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      1 This is ld.info, produced by makeinfo version 4.13 from
      2 /tmp/android-1596/src/build/../binutils/binutils-2.21/ld/ld.texinfo.
      3 
      4 INFO-DIR-SECTION Software development
      5 START-INFO-DIR-ENTRY
      6 * Ld: (ld).                       The GNU linker.
      7 END-INFO-DIR-ENTRY
      8 
      9    This file documents the GNU linker LD (GNU Binutils) version 2.21.
     10 
     11    Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
     12 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free
     13 Software Foundation, Inc.
     14 
     15    Permission is granted to copy, distribute and/or modify this document
     16 under the terms of the GNU Free Documentation License, Version 1.3 or
     17 any later version published by the Free Software Foundation; with no
     18 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
     19 Texts.  A copy of the license is included in the section entitled "GNU
     20 Free Documentation License".
     21 
     22 
     23 File: ld.info,  Node: Top,  Next: Overview,  Up: (dir)
     24 
     25 LD
     26 **
     27 
     28 This file documents the GNU linker ld (GNU Binutils) version 2.21.
     29 
     30    This document is distributed under the terms of the GNU Free
     31 Documentation License version 1.3.  A copy of the license is included
     32 in the section entitled "GNU Free Documentation License".
     33 
     34 * Menu:
     35 
     36 * Overview::                    Overview
     37 * Invocation::                  Invocation
     38 * Scripts::                     Linker Scripts
     39 
     40 * Machine Dependent::           Machine Dependent Features
     41 
     42 * BFD::                         BFD
     43 
     44 * Reporting Bugs::              Reporting Bugs
     45 * MRI::                         MRI Compatible Script Files
     46 * GNU Free Documentation License::  GNU Free Documentation License
     47 * LD Index::                       LD Index
     48 
     49 
     50 File: ld.info,  Node: Overview,  Next: Invocation,  Prev: Top,  Up: Top
     51 
     52 1 Overview
     53 **********
     54 
     55 `ld' combines a number of object and archive files, relocates their
     56 data and ties up symbol references. Usually the last step in compiling
     57 a program is to run `ld'.
     58 
     59    `ld' accepts Linker Command Language files written in a superset of
     60 AT&T's Link Editor Command Language syntax, to provide explicit and
     61 total control over the linking process.
     62 
     63    This version of `ld' uses the general purpose BFD libraries to
     64 operate on object files. This allows `ld' to read, combine, and write
     65 object files in many different formats--for example, COFF or `a.out'.
     66 Different formats may be linked together to produce any available kind
     67 of object file.  *Note BFD::, for more information.
     68 
     69    Aside from its flexibility, the GNU linker is more helpful than other
     70 linkers in providing diagnostic information.  Many linkers abandon
     71 execution immediately upon encountering an error; whenever possible,
     72 `ld' continues executing, allowing you to identify other errors (or, in
     73 some cases, to get an output file in spite of the error).
     74 
     75 
     76 File: ld.info,  Node: Invocation,  Next: Scripts,  Prev: Overview,  Up: Top
     77 
     78 2 Invocation
     79 ************
     80 
     81 The GNU linker `ld' is meant to cover a broad range of situations, and
     82 to be as compatible as possible with other linkers.  As a result, you
     83 have many choices to control its behavior.
     84 
     85 * Menu:
     86 
     87 * Options::                     Command Line Options
     88 * Environment::                 Environment Variables
     89 
     90 
     91 File: ld.info,  Node: Options,  Next: Environment,  Up: Invocation
     92 
     93 2.1 Command Line Options
     94 ========================
     95 
     96    The linker supports a plethora of command-line options, but in actual
     97 practice few of them are used in any particular context.  For instance,
     98 a frequent use of `ld' is to link standard Unix object files on a
     99 standard, supported Unix system.  On such a system, to link a file
    100 `hello.o':
    101 
    102      ld -o OUTPUT /lib/crt0.o hello.o -lc
    103 
    104    This tells `ld' to produce a file called OUTPUT as the result of
    105 linking the file `/lib/crt0.o' with `hello.o' and the library `libc.a',
    106 which will come from the standard search directories.  (See the
    107 discussion of the `-l' option below.)
    108 
    109    Some of the command-line options to `ld' may be specified at any
    110 point in the command line.  However, options which refer to files, such
    111 as `-l' or `-T', cause the file to be read at the point at which the
    112 option appears in the command line, relative to the object files and
    113 other file options.  Repeating non-file options with a different
    114 argument will either have no further effect, or override prior
    115 occurrences (those further to the left on the command line) of that
    116 option.  Options which may be meaningfully specified more than once are
    117 noted in the descriptions below.
    118 
    119    Non-option arguments are object files or archives which are to be
    120 linked together.  They may follow, precede, or be mixed in with
    121 command-line options, except that an object file argument may not be
    122 placed between an option and its argument.
    123 
    124    Usually the linker is invoked with at least one object file, but you
    125 can specify other forms of binary input files using `-l', `-R', and the
    126 script command language.  If _no_ binary input files at all are
    127 specified, the linker does not produce any output, and issues the
    128 message `No input files'.
    129 
    130    If the linker cannot recognize the format of an object file, it will
    131 assume that it is a linker script.  A script specified in this way
    132 augments the main linker script used for the link (either the default
    133 linker script or the one specified by using `-T').  This feature
    134 permits the linker to link against a file which appears to be an object
    135 or an archive, but actually merely defines some symbol values, or uses
    136 `INPUT' or `GROUP' to load other objects.  Specifying a script in this
    137 way merely augments the main linker script, with the extra commands
    138 placed after the main script; use the `-T' option to replace the
    139 default linker script entirely, but note the effect of the `INSERT'
    140 command.  *Note Scripts::.
    141 
    142    For options whose names are a single letter, option arguments must
    143 either follow the option letter without intervening whitespace, or be
    144 given as separate arguments immediately following the option that
    145 requires them.
    146 
    147    For options whose names are multiple letters, either one dash or two
    148 can precede the option name; for example, `-trace-symbol' and
    149 `--trace-symbol' are equivalent.  Note--there is one exception to this
    150 rule.  Multiple letter options that start with a lower case 'o' can
    151 only be preceded by two dashes.  This is to reduce confusion with the
    152 `-o' option.  So for example `-omagic' sets the output file name to
    153 `magic' whereas `--omagic' sets the NMAGIC flag on the output.
    154 
    155    Arguments to multiple-letter options must either be separated from
    156 the option name by an equals sign, or be given as separate arguments
    157 immediately following the option that requires them.  For example,
    158 `--trace-symbol foo' and `--trace-symbol=foo' are equivalent.  Unique
    159 abbreviations of the names of multiple-letter options are accepted.
    160 
    161    Note--if the linker is being invoked indirectly, via a compiler
    162 driver (e.g. `gcc') then all the linker command line options should be
    163 prefixed by `-Wl,' (or whatever is appropriate for the particular
    164 compiler driver) like this:
    165 
    166        gcc -Wl,--start-group foo.o bar.o -Wl,--end-group
    167 
    168    This is important, because otherwise the compiler driver program may
    169 silently drop the linker options, resulting in a bad link.  Confusion
    170 may also arise when passing options that require values through a
    171 driver, as the use of a space between option and argument acts as a
    172 separator, and causes the driver to pass only the option to the linker
    173 and the argument to the compiler.  In this case, it is simplest to use
    174 the joined forms of both single- and multiple-letter options, such as:
    175 
    176        gcc foo.o bar.o -Wl,-eENTRY -Wl,-Map=a.map
    177 
    178    Here is a table of the generic command line switches accepted by the
    179 GNU linker:
    180 
    181 `@FILE'
    182      Read command-line options from FILE.  The options read are
    183      inserted in place of the original @FILE option.  If FILE does not
    184      exist, or cannot be read, then the option will be treated
    185      literally, and not removed.
    186 
    187      Options in FILE are separated by whitespace.  A whitespace
    188      character may be included in an option by surrounding the entire
    189      option in either single or double quotes.  Any character
    190      (including a backslash) may be included by prefixing the character
    191      to be included with a backslash.  The FILE may itself contain
    192      additional @FILE options; any such options will be processed
    193      recursively.
    194 
    195 `-a KEYWORD'
    196      This option is supported for HP/UX compatibility.  The KEYWORD
    197      argument must be one of the strings `archive', `shared', or
    198      `default'.  `-aarchive' is functionally equivalent to `-Bstatic',
    199      and the other two keywords are functionally equivalent to
    200      `-Bdynamic'.  This option may be used any number of times.
    201 
    202 `--audit AUDITLIB'
    203      Adds AUDITLIB to the `DT_AUDIT' entry of the dynamic section.
    204      AUDITLIB is not checked for existence, nor will it use the
    205      DT_SONAME specified in the library.  If specified multiple times
    206      `DT_AUDIT' will contain a colon separated list of audit interfaces
    207      to use. If the linker finds an object with an audit entry while
    208      searching for shared libraries, it will add a corresponding
    209      `DT_DEPAUDIT' entry in the output file.  This option is only
    210      meaningful on ELF platforms supporting the rtld-audit interface.
    211 
    212 `-A ARCHITECTURE'
    213 `--architecture=ARCHITECTURE'
    214      In the current release of `ld', this option is useful only for the
    215      Intel 960 family of architectures.  In that `ld' configuration, the
    216      ARCHITECTURE argument identifies the particular architecture in
    217      the 960 family, enabling some safeguards and modifying the
    218      archive-library search path.  *Note `ld' and the Intel 960 family:
    219      i960, for details.
    220 
    221      Future releases of `ld' may support similar functionality for
    222      other architecture families.
    223 
    224 `-b INPUT-FORMAT'
    225 `--format=INPUT-FORMAT'
    226      `ld' may be configured to support more than one kind of object
    227      file.  If your `ld' is configured this way, you can use the `-b'
    228      option to specify the binary format for input object files that
    229      follow this option on the command line.  Even when `ld' is
    230      configured to support alternative object formats, you don't
    231      usually need to specify this, as `ld' should be configured to
    232      expect as a default input format the most usual format on each
    233      machine.  INPUT-FORMAT is a text string, the name of a particular
    234      format supported by the BFD libraries.  (You can list the
    235      available binary formats with `objdump -i'.)  *Note BFD::.
    236 
    237      You may want to use this option if you are linking files with an
    238      unusual binary format.  You can also use `-b' to switch formats
    239      explicitly (when linking object files of different formats), by
    240      including `-b INPUT-FORMAT' before each group of object files in a
    241      particular format.
    242 
    243      The default format is taken from the environment variable
    244      `GNUTARGET'.  *Note Environment::.  You can also define the input
    245      format from a script, using the command `TARGET'; see *note Format
    246      Commands::.
    247 
    248 `-c MRI-COMMANDFILE'
    249 `--mri-script=MRI-COMMANDFILE'
    250      For compatibility with linkers produced by MRI, `ld' accepts script
    251      files written in an alternate, restricted command language,
    252      described in *note MRI Compatible Script Files: MRI.  Introduce
    253      MRI script files with the option `-c'; use the `-T' option to run
    254      linker scripts written in the general-purpose `ld' scripting
    255      language.  If MRI-CMDFILE does not exist, `ld' looks for it in the
    256      directories specified by any `-L' options.
    257 
    258 `-d'
    259 `-dc'
    260 `-dp'
    261      These three options are equivalent; multiple forms are supported
    262      for compatibility with other linkers.  They assign space to common
    263      symbols even if a relocatable output file is specified (with
    264      `-r').  The script command `FORCE_COMMON_ALLOCATION' has the same
    265      effect.  *Note Miscellaneous Commands::.
    266 
    267 `--depaudit AUDITLIB'
    268 `-P AUDITLIB'
    269      Adds AUDITLIB to the `DT_DEPAUDIT' entry of the dynamic section.
    270      AUDITLIB is not checked for existence, nor will it use the
    271      DT_SONAME specified in the library.  If specified multiple times
    272      `DT_DEPAUDIT' will contain a colon separated list of audit
    273      interfaces to use.  This option is only meaningful on ELF
    274      platforms supporting the rtld-audit interface.  The -P option is
    275      provided for Solaris compatibility.
    276 
    277 `-e ENTRY'
    278 `--entry=ENTRY'
    279      Use ENTRY as the explicit symbol for beginning execution of your
    280      program, rather than the default entry point.  If there is no
    281      symbol named ENTRY, the linker will try to parse ENTRY as a number,
    282      and use that as the entry address (the number will be interpreted
    283      in base 10; you may use a leading `0x' for base 16, or a leading
    284      `0' for base 8).  *Note Entry Point::, for a discussion of defaults
    285      and other ways of specifying the entry point.
    286 
    287 `--exclude-libs LIB,LIB,...'
    288      Specifies a list of archive libraries from which symbols should
    289      not be automatically exported.  The library names may be delimited
    290      by commas or colons.  Specifying `--exclude-libs ALL' excludes
    291      symbols in all archive libraries from automatic export.  This
    292      option is available only for the i386 PE targeted port of the
    293      linker and for ELF targeted ports.  For i386 PE, symbols
    294      explicitly listed in a .def file are still exported, regardless of
    295      this option.  For ELF targeted ports, symbols affected by this
    296      option will be treated as hidden.
    297 
    298 `--exclude-modules-for-implib MODULE,MODULE,...'
    299      Specifies a list of object files or archive members, from which
    300      symbols should not be automatically exported, but which should be
    301      copied wholesale into the import library being generated during
    302      the link.  The module names may be delimited by commas or colons,
    303      and must match exactly the filenames used by `ld' to open the
    304      files; for archive members, this is simply the member name, but
    305      for object files the name listed must include and match precisely
    306      any path used to specify the input file on the linker's
    307      command-line.  This option is available only for the i386 PE
    308      targeted port of the linker.  Symbols explicitly listed in a .def
    309      file are still exported, regardless of this option.
    310 
    311 `-E'
    312 `--export-dynamic'
    313 `--no-export-dynamic'
    314      When creating a dynamically linked executable, using the `-E'
    315      option or the `--export-dynamic' option causes the linker to add
    316      all symbols to the dynamic symbol table.  The dynamic symbol table
    317      is the set of symbols which are visible from dynamic objects at
    318      run time.
    319 
    320      If you do not use either of these options (or use the
    321      `--no-export-dynamic' option to restore the default behavior), the
    322      dynamic symbol table will normally contain only those symbols
    323      which are referenced by some dynamic object mentioned in the link.
    324 
    325      If you use `dlopen' to load a dynamic object which needs to refer
    326      back to the symbols defined by the program, rather than some other
    327      dynamic object, then you will probably need to use this option when
    328      linking the program itself.
    329 
    330      You can also use the dynamic list to control what symbols should
    331      be added to the dynamic symbol table if the output format supports
    332      it.  See the description of `--dynamic-list'.
    333 
    334      Note that this option is specific to ELF targeted ports.  PE
    335      targets support a similar function to export all symbols from a
    336      DLL or EXE; see the description of `--export-all-symbols' below.
    337 
    338 `-EB'
    339      Link big-endian objects.  This affects the default output format.
    340 
    341 `-EL'
    342      Link little-endian objects.  This affects the default output
    343      format.
    344 
    345 `-f NAME'
    346 `--auxiliary=NAME'
    347      When creating an ELF shared object, set the internal DT_AUXILIARY
    348      field to the specified name.  This tells the dynamic linker that
    349      the symbol table of the shared object should be used as an
    350      auxiliary filter on the symbol table of the shared object NAME.
    351 
    352      If you later link a program against this filter object, then, when
    353      you run the program, the dynamic linker will see the DT_AUXILIARY
    354      field.  If the dynamic linker resolves any symbols from the filter
    355      object, it will first check whether there is a definition in the
    356      shared object NAME.  If there is one, it will be used instead of
    357      the definition in the filter object.  The shared object NAME need
    358      not exist.  Thus the shared object NAME may be used to provide an
    359      alternative implementation of certain functions, perhaps for
    360      debugging or for machine specific performance.
    361 
    362      This option may be specified more than once.  The DT_AUXILIARY
    363      entries will be created in the order in which they appear on the
    364      command line.
    365 
    366 `-F NAME'
    367 `--filter=NAME'
    368      When creating an ELF shared object, set the internal DT_FILTER
    369      field to the specified name.  This tells the dynamic linker that
    370      the symbol table of the shared object which is being created
    371      should be used as a filter on the symbol table of the shared
    372      object NAME.
    373 
    374      If you later link a program against this filter object, then, when
    375      you run the program, the dynamic linker will see the DT_FILTER
    376      field.  The dynamic linker will resolve symbols according to the
    377      symbol table of the filter object as usual, but it will actually
    378      link to the definitions found in the shared object NAME.  Thus the
    379      filter object can be used to select a subset of the symbols
    380      provided by the object NAME.
    381 
    382      Some older linkers used the `-F' option throughout a compilation
    383      toolchain for specifying object-file format for both input and
    384      output object files.  The GNU linker uses other mechanisms for
    385      this purpose: the `-b', `--format', `--oformat' options, the
    386      `TARGET' command in linker scripts, and the `GNUTARGET'
    387      environment variable.  The GNU linker will ignore the `-F' option
    388      when not creating an ELF shared object.
    389 
    390 `-fini=NAME'
    391      When creating an ELF executable or shared object, call NAME when
    392      the executable or shared object is unloaded, by setting DT_FINI to
    393      the address of the function.  By default, the linker uses `_fini'
    394      as the function to call.
    395 
    396 `-g'
    397      Ignored.  Provided for compatibility with other tools.
    398 
    399 `-G VALUE'
    400 `--gpsize=VALUE'
    401      Set the maximum size of objects to be optimized using the GP
    402      register to SIZE.  This is only meaningful for object file formats
    403      such as MIPS ECOFF which supports putting large and small objects
    404      into different sections.  This is ignored for other object file
    405      formats.
    406 
    407 `-h NAME'
    408 `-soname=NAME'
    409      When creating an ELF shared object, set the internal DT_SONAME
    410      field to the specified name.  When an executable is linked with a
    411      shared object which has a DT_SONAME field, then when the
    412      executable is run the dynamic linker will attempt to load the
    413      shared object specified by the DT_SONAME field rather than the
    414      using the file name given to the linker.
    415 
    416 `-i'
    417      Perform an incremental link (same as option `-r').
    418 
    419 `-init=NAME'
    420      When creating an ELF executable or shared object, call NAME when
    421      the executable or shared object is loaded, by setting DT_INIT to
    422      the address of the function.  By default, the linker uses `_init'
    423      as the function to call.
    424 
    425 `-l NAMESPEC'
    426 `--library=NAMESPEC'
    427      Add the archive or object file specified by NAMESPEC to the list
    428      of files to link.  This option may be used any number of times.
    429      If NAMESPEC is of the form `:FILENAME', `ld' will search the
    430      library path for a file called FILENAME, otherwise it will search
    431      the library path for a file called `libNAMESPEC.a'.
    432 
    433      On systems which support shared libraries, `ld' may also search for
    434      files other than `libNAMESPEC.a'.  Specifically, on ELF and SunOS
    435      systems, `ld' will search a directory for a library called
    436      `libNAMESPEC.so' before searching for one called `libNAMESPEC.a'.
    437      (By convention, a `.so' extension indicates a shared library.)
    438      Note that this behavior does not apply to `:FILENAME', which
    439      always specifies a file called FILENAME.
    440 
    441      The linker will search an archive only once, at the location where
    442      it is specified on the command line.  If the archive defines a
    443      symbol which was undefined in some object which appeared before
    444      the archive on the command line, the linker will include the
    445      appropriate file(s) from the archive.  However, an undefined
    446      symbol in an object appearing later on the command line will not
    447      cause the linker to search the archive again.
    448 
    449      See the `-(' option for a way to force the linker to search
    450      archives multiple times.
    451 
    452      You may list the same archive multiple times on the command line.
    453 
    454      This type of archive searching is standard for Unix linkers.
    455      However, if you are using `ld' on AIX, note that it is different
    456      from the behaviour of the AIX linker.
    457 
    458 `-L SEARCHDIR'
    459 `--library-path=SEARCHDIR'
    460      Add path SEARCHDIR to the list of paths that `ld' will search for
    461      archive libraries and `ld' control scripts.  You may use this
    462      option any number of times.  The directories are searched in the
    463      order in which they are specified on the command line.
    464      Directories specified on the command line are searched before the
    465      default directories.  All `-L' options apply to all `-l' options,
    466      regardless of the order in which the options appear.  `-L' options
    467      do not affect how `ld' searches for a linker script unless `-T'
    468      option is specified.
    469 
    470      If SEARCHDIR begins with `=', then the `=' will be replaced by the
    471      "sysroot prefix", a path specified when the linker is configured.
    472 
    473      The default set of paths searched (without being specified with
    474      `-L') depends on which emulation mode `ld' is using, and in some
    475      cases also on how it was configured.  *Note Environment::.
    476 
    477      The paths can also be specified in a link script with the
    478      `SEARCH_DIR' command.  Directories specified this way are searched
    479      at the point in which the linker script appears in the command
    480      line.
    481 
    482 `-m EMULATION'
    483      Emulate the EMULATION linker.  You can list the available
    484      emulations with the `--verbose' or `-V' options.
    485 
    486      If the `-m' option is not used, the emulation is taken from the
    487      `LDEMULATION' environment variable, if that is defined.
    488 
    489      Otherwise, the default emulation depends upon how the linker was
    490      configured.
    491 
    492 `-M'
    493 `--print-map'
    494      Print a link map to the standard output.  A link map provides
    495      information about the link, including the following:
    496 
    497         * Where object files are mapped into memory.
    498 
    499         * How common symbols are allocated.
    500 
    501         * All archive members included in the link, with a mention of
    502           the symbol which caused the archive member to be brought in.
    503 
    504         * The values assigned to symbols.
    505 
    506           Note - symbols whose values are computed by an expression
    507           which involves a reference to a previous value of the same
    508           symbol may not have correct result displayed in the link map.
    509           This is because the linker discards intermediate results and
    510           only retains the final value of an expression.  Under such
    511           circumstances the linker will display the final value
    512           enclosed by square brackets.  Thus for example a linker
    513           script containing:
    514 
    515                   foo = 1
    516                   foo = foo * 4
    517                   foo = foo + 8
    518 
    519           will produce the following output in the link map if the `-M'
    520           option is used:
    521 
    522                   0x00000001                foo = 0x1
    523                   [0x0000000c]                foo = (foo * 0x4)
    524                   [0x0000000c]                foo = (foo + 0x8)
    525 
    526           See *note Expressions:: for more information about
    527           expressions in linker scripts.
    528 
    529 `-n'
    530 `--nmagic'
    531      Turn off page alignment of sections, and disable linking against
    532      shared libraries.  If the output format supports Unix style magic
    533      numbers, mark the output as `NMAGIC'.
    534 
    535 `-N'
    536 `--omagic'
    537      Set the text and data sections to be readable and writable.  Also,
    538      do not page-align the data segment, and disable linking against
    539      shared libraries.  If the output format supports Unix style magic
    540      numbers, mark the output as `OMAGIC'. Note: Although a writable
    541      text section is allowed for PE-COFF targets, it does not conform
    542      to the format specification published by Microsoft.
    543 
    544 `--no-omagic'
    545      This option negates most of the effects of the `-N' option.  It
    546      sets the text section to be read-only, and forces the data segment
    547      to be page-aligned.  Note - this option does not enable linking
    548      against shared libraries.  Use `-Bdynamic' for this.
    549 
    550 `-o OUTPUT'
    551 `--output=OUTPUT'
    552      Use OUTPUT as the name for the program produced by `ld'; if this
    553      option is not specified, the name `a.out' is used by default.  The
    554      script command `OUTPUT' can also specify the output file name.
    555 
    556 `-O LEVEL'
    557      If LEVEL is a numeric values greater than zero `ld' optimizes the
    558      output.  This might take significantly longer and therefore
    559      probably should only be enabled for the final binary.  At the
    560      moment this option only affects ELF shared library generation.
    561      Future releases of the linker may make more use of this option.
    562      Also currently there is no difference in the linker's behaviour
    563      for different non-zero values of this option.  Again this may
    564      change with future releases.
    565 
    566 `-q'
    567 `--emit-relocs'
    568      Leave relocation sections and contents in fully linked executables.
    569      Post link analysis and optimization tools may need this
    570      information in order to perform correct modifications of
    571      executables.  This results in larger executables.
    572 
    573      This option is currently only supported on ELF platforms.
    574 
    575 `--force-dynamic'
    576      Force the output file to have dynamic sections.  This option is
    577      specific to VxWorks targets.
    578 
    579 `-r'
    580 `--relocatable'
    581      Generate relocatable output--i.e., generate an output file that
    582      can in turn serve as input to `ld'.  This is often called "partial
    583      linking".  As a side effect, in environments that support standard
    584      Unix magic numbers, this option also sets the output file's magic
    585      number to `OMAGIC'.  If this option is not specified, an absolute
    586      file is produced.  When linking C++ programs, this option _will
    587      not_ resolve references to constructors; to do that, use `-Ur'.
    588 
    589      When an input file does not have the same format as the output
    590      file, partial linking is only supported if that input file does
    591      not contain any relocations.  Different output formats can have
    592      further restrictions; for example some `a.out'-based formats do
    593      not support partial linking with input files in other formats at
    594      all.
    595 
    596      This option does the same thing as `-i'.
    597 
    598 `-R FILENAME'
    599 `--just-symbols=FILENAME'
    600      Read symbol names and their addresses from FILENAME, but do not
    601      relocate it or include it in the output.  This allows your output
    602      file to refer symbolically to absolute locations of memory defined
    603      in other programs.  You may use this option more than once.
    604 
    605      For compatibility with other ELF linkers, if the `-R' option is
    606      followed by a directory name, rather than a file name, it is
    607      treated as the `-rpath' option.
    608 
    609 `-s'
    610 `--strip-all'
    611      Omit all symbol information from the output file.
    612 
    613 `-S'
    614 `--strip-debug'
    615      Omit debugger symbol information (but not all symbols) from the
    616      output file.
    617 
    618 `-t'
    619 `--trace'
    620      Print the names of the input files as `ld' processes them.
    621 
    622 `-T SCRIPTFILE'
    623 `--script=SCRIPTFILE'
    624      Use SCRIPTFILE as the linker script.  This script replaces `ld''s
    625      default linker script (rather than adding to it), so COMMANDFILE
    626      must specify everything necessary to describe the output file.
    627      *Note Scripts::.  If SCRIPTFILE does not exist in the current
    628      directory, `ld' looks for it in the directories specified by any
    629      preceding `-L' options.  Multiple `-T' options accumulate.
    630 
    631 `-dT SCRIPTFILE'
    632 `--default-script=SCRIPTFILE'
    633      Use SCRIPTFILE as the default linker script.  *Note Scripts::.
    634 
    635      This option is similar to the `--script' option except that
    636      processing of the script is delayed until after the rest of the
    637      command line has been processed.  This allows options placed after
    638      the `--default-script' option on the command line to affect the
    639      behaviour of the linker script, which can be important when the
    640      linker command line cannot be directly controlled by the user.
    641      (eg because the command line is being constructed by another tool,
    642      such as `gcc').
    643 
    644 `-u SYMBOL'
    645 `--undefined=SYMBOL'
    646      Force SYMBOL to be entered in the output file as an undefined
    647      symbol.  Doing this may, for example, trigger linking of additional
    648      modules from standard libraries.  `-u' may be repeated with
    649      different option arguments to enter additional undefined symbols.
    650      This option is equivalent to the `EXTERN' linker script command.
    651 
    652 `-Ur'
    653      For anything other than C++ programs, this option is equivalent to
    654      `-r': it generates relocatable output--i.e., an output file that
    655      can in turn serve as input to `ld'.  When linking C++ programs,
    656      `-Ur' _does_ resolve references to constructors, unlike `-r'.  It
    657      does not work to use `-Ur' on files that were themselves linked
    658      with `-Ur'; once the constructor table has been built, it cannot
    659      be added to.  Use `-Ur' only for the last partial link, and `-r'
    660      for the others.
    661 
    662 `--unique[=SECTION]'
    663      Creates a separate output section for every input section matching
    664      SECTION, or if the optional wildcard SECTION argument is missing,
    665      for every orphan input section.  An orphan section is one not
    666      specifically mentioned in a linker script.  You may use this option
    667      multiple times on the command line;  It prevents the normal
    668      merging of input sections with the same name, overriding output
    669      section assignments in a linker script.
    670 
    671 `-v'
    672 `--version'
    673 `-V'
    674      Display the version number for `ld'.  The `-V' option also lists
    675      the supported emulations.
    676 
    677 `-x'
    678 `--discard-all'
    679      Delete all local symbols.
    680 
    681 `-X'
    682 `--discard-locals'
    683      Delete all temporary local symbols.  (These symbols start with
    684      system-specific local label prefixes, typically `.L' for ELF
    685      systems or `L' for traditional a.out systems.)
    686 
    687 `-y SYMBOL'
    688 `--trace-symbol=SYMBOL'
    689      Print the name of each linked file in which SYMBOL appears.  This
    690      option may be given any number of times.  On many systems it is
    691      necessary to prepend an underscore.
    692 
    693      This option is useful when you have an undefined symbol in your
    694      link but don't know where the reference is coming from.
    695 
    696 `-Y PATH'
    697      Add PATH to the default library search path.  This option exists
    698      for Solaris compatibility.
    699 
    700 `-z KEYWORD'
    701      The recognized keywords are:
    702     `combreloc'
    703           Combines multiple reloc sections and sorts them to make
    704           dynamic symbol lookup caching possible.
    705 
    706     `defs'
    707           Disallows undefined symbols in object files.  Undefined
    708           symbols in shared libraries are still allowed.
    709 
    710     `execstack'
    711           Marks the object as requiring executable stack.
    712 
    713     `initfirst'
    714           This option is only meaningful when building a shared object.
    715           It marks the object so that its runtime initialization will
    716           occur before the runtime initialization of any other objects
    717           brought into the process at the same time.  Similarly the
    718           runtime finalization of the object will occur after the
    719           runtime finalization of any other objects.
    720 
    721     `interpose'
    722           Marks the object that its symbol table interposes before all
    723           symbols but the primary executable.
    724 
    725     `lazy'
    726           When generating an executable or shared library, mark it to
    727           tell the dynamic linker to defer function call resolution to
    728           the point when the function is called (lazy binding), rather
    729           than at load time.  Lazy binding is the default.
    730 
    731     `loadfltr'
    732           Marks  the object that its filters be processed immediately at
    733           runtime.
    734 
    735     `muldefs'
    736           Allows multiple definitions.
    737 
    738     `nocombreloc'
    739           Disables multiple reloc sections combining.
    740 
    741     `nocopyreloc'
    742           Disables production of copy relocs.
    743 
    744     `nodefaultlib'
    745           Marks the object that the search for dependencies of this
    746           object will ignore any default library search paths.
    747 
    748     `nodelete'
    749           Marks the object shouldn't be unloaded at runtime.
    750 
    751     `nodlopen'
    752           Marks the object not available to `dlopen'.
    753 
    754     `nodump'
    755           Marks the object can not be dumped by `dldump'.
    756 
    757     `noexecstack'
    758           Marks the object as not requiring executable stack.
    759 
    760     `norelro'
    761           Don't create an ELF `PT_GNU_RELRO' segment header in the
    762           object.
    763 
    764     `now'
    765           When generating an executable or shared library, mark it to
    766           tell the dynamic linker to resolve all symbols when the
    767           program is started, or when the shared library is linked to
    768           using dlopen, instead of deferring function call resolution
    769           to the point when the function is first called.
    770 
    771     `origin'
    772           Marks the object may contain $ORIGIN.
    773 
    774     `relro'
    775           Create an ELF `PT_GNU_RELRO' segment header in the object.
    776 
    777     `max-page-size=VALUE'
    778           Set the emulation maximum page size to VALUE.
    779 
    780     `common-page-size=VALUE'
    781           Set the emulation common page size to VALUE.
    782 
    783 
    784      Other keywords are ignored for Solaris compatibility.
    785 
    786 `-( ARCHIVES -)'
    787 `--start-group ARCHIVES --end-group'
    788      The ARCHIVES should be a list of archive files.  They may be
    789      either explicit file names, or `-l' options.
    790 
    791      The specified archives are searched repeatedly until no new
    792      undefined references are created.  Normally, an archive is
    793      searched only once in the order that it is specified on the
    794      command line.  If a symbol in that archive is needed to resolve an
    795      undefined symbol referred to by an object in an archive that
    796      appears later on the command line, the linker would not be able to
    797      resolve that reference.  By grouping the archives, they all be
    798      searched repeatedly until all possible references are resolved.
    799 
    800      Using this option has a significant performance cost.  It is best
    801      to use it only when there are unavoidable circular references
    802      between two or more archives.
    803 
    804 `--accept-unknown-input-arch'
    805 `--no-accept-unknown-input-arch'
    806      Tells the linker to accept input files whose architecture cannot be
    807      recognised.  The assumption is that the user knows what they are
    808      doing and deliberately wants to link in these unknown input files.
    809      This was the default behaviour of the linker, before release 2.14.
    810      The default behaviour from release 2.14 onwards is to reject such
    811      input files, and so the `--accept-unknown-input-arch' option has
    812      been added to restore the old behaviour.
    813 
    814 `--as-needed'
    815 `--no-as-needed'
    816      This option affects ELF DT_NEEDED tags for dynamic libraries
    817      mentioned on the command line after the `--as-needed' option.
    818      Normally the linker will add a DT_NEEDED tag for each dynamic
    819      library mentioned on the command line, regardless of whether the
    820      library is actually needed or not.  `--as-needed' causes a
    821      DT_NEEDED tag to only be emitted for a library that satisfies an
    822      undefined symbol reference from a regular object file or, if the
    823      library is not found in the DT_NEEDED lists of other libraries
    824      linked up to that point, an undefined symbol reference from
    825      another dynamic library.  `--no-as-needed' restores the default
    826      behaviour.
    827 
    828 `--add-needed'
    829 `--no-add-needed'
    830      These two options have been deprecated because of the similarity of
    831      their names to the `--as-needed' and `--no-as-needed' options.
    832      They have been replaced by `--copy-dt-needed-entries' and
    833      `--no-copy-dt-needed-entries'.
    834 
    835 `-assert KEYWORD'
    836      This option is ignored for SunOS compatibility.
    837 
    838 `-Bdynamic'
    839 `-dy'
    840 `-call_shared'
    841      Link against dynamic libraries.  This is only meaningful on
    842      platforms for which shared libraries are supported.  This option
    843      is normally the default on such platforms.  The different variants
    844      of this option are for compatibility with various systems.  You
    845      may use this option multiple times on the command line: it affects
    846      library searching for `-l' options which follow it.
    847 
    848 `-Bgroup'
    849      Set the `DF_1_GROUP' flag in the `DT_FLAGS_1' entry in the dynamic
    850      section.  This causes the runtime linker to handle lookups in this
    851      object and its dependencies to be performed only inside the group.
    852      `--unresolved-symbols=report-all' is implied.  This option is only
    853      meaningful on ELF platforms which support shared libraries.
    854 
    855 `-Bstatic'
    856 `-dn'
    857 `-non_shared'
    858 `-static'
    859      Do not link against shared libraries.  This is only meaningful on
    860      platforms for which shared libraries are supported.  The different
    861      variants of this option are for compatibility with various
    862      systems.  You may use this option multiple times on the command
    863      line: it affects library searching for `-l' options which follow
    864      it.  This option also implies `--unresolved-symbols=report-all'.
    865      This option can be used with `-shared'.  Doing so means that a
    866      shared library is being created but that all of the library's
    867      external references must be resolved by pulling in entries from
    868      static libraries.
    869 
    870 `-Bsymbolic'
    871      When creating a shared library, bind references to global symbols
    872      to the definition within the shared library, if any.  Normally, it
    873      is possible for a program linked against a shared library to
    874      override the definition within the shared library.  This option is
    875      only meaningful on ELF platforms which support shared libraries.
    876 
    877 `-Bsymbolic-functions'
    878      When creating a shared library, bind references to global function
    879      symbols to the definition within the shared library, if any.  This
    880      option is only meaningful on ELF platforms which support shared
    881      libraries.
    882 
    883 `--dynamic-list=DYNAMIC-LIST-FILE'
    884      Specify the name of a dynamic list file to the linker.  This is
    885      typically used when creating shared libraries to specify a list of
    886      global symbols whose references shouldn't be bound to the
    887      definition within the shared library, or creating dynamically
    888      linked executables to specify a list of symbols which should be
    889      added to the symbol table in the executable.  This option is only
    890      meaningful on ELF platforms which support shared libraries.
    891 
    892      The format of the dynamic list is the same as the version node
    893      without scope and node name.  See *note VERSION:: for more
    894      information.
    895 
    896 `--dynamic-list-data'
    897      Include all global data symbols to the dynamic list.
    898 
    899 `--dynamic-list-cpp-new'
    900      Provide the builtin dynamic list for C++ operator new and delete.
    901      It is mainly useful for building shared libstdc++.
    902 
    903 `--dynamic-list-cpp-typeinfo'
    904      Provide the builtin dynamic list for C++ runtime type
    905      identification.
    906 
    907 `--check-sections'
    908 `--no-check-sections'
    909      Asks the linker _not_ to check section addresses after they have
    910      been assigned to see if there are any overlaps.  Normally the
    911      linker will perform this check, and if it finds any overlaps it
    912      will produce suitable error messages.  The linker does know about,
    913      and does make allowances for sections in overlays.  The default
    914      behaviour can be restored by using the command line switch
    915      `--check-sections'.  Section overlap is not usually checked for
    916      relocatable links.  You can force checking in that case by using
    917      the `--check-sections' option.
    918 
    919 `--copy-dt-needed-entries'
    920 `--no-copy-dt-needed-entries'
    921      This option affects the treatment of dynamic libraries referred to
    922      by DT_NEEDED tags _inside_ ELF dynamic libraries mentioned on the
    923      command line.  Normally the linker will add a DT_NEEDED tag to the
    924      output binary for each library mentioned in a DT_NEEDED tag in an
    925      input dynamic library.  With `--no-copy-dt-needed-entries'
    926      specified on the command line however any dynamic libraries that
    927      follow it will have their DT_NEEDED entries ignored.  The default
    928      behaviour can be restored with `--copy-dt-needed-entries'.
    929 
    930      This option also has an effect on the resolution of symbols in
    931      dynamic libraries.  With the default setting dynamic libraries
    932      mentioned on the command line will be recursively searched,
    933      following their DT_NEEDED tags to other libraries, in order to
    934      resolve symbols required by the output binary.  With
    935      `--no-copy-dt-needed-entries' specified however the searching of
    936      dynamic libraries that follow it will stop with the dynamic
    937      library itself.  No DT_NEEDED links will be traversed to resolve
    938      symbols.
    939 
    940 `--cref'
    941      Output a cross reference table.  If a linker map file is being
    942      generated, the cross reference table is printed to the map file.
    943      Otherwise, it is printed on the standard output.
    944 
    945      The format of the table is intentionally simple, so that it may be
    946      easily processed by a script if necessary.  The symbols are
    947      printed out, sorted by name.  For each symbol, a list of file
    948      names is given.  If the symbol is defined, the first file listed
    949      is the location of the definition.  The remaining files contain
    950      references to the symbol.
    951 
    952 `--no-define-common'
    953      This option inhibits the assignment of addresses to common symbols.
    954      The script command `INHIBIT_COMMON_ALLOCATION' has the same effect.
    955      *Note Miscellaneous Commands::.
    956 
    957      The `--no-define-common' option allows decoupling the decision to
    958      assign addresses to Common symbols from the choice of the output
    959      file type; otherwise a non-Relocatable output type forces
    960      assigning addresses to Common symbols.  Using `--no-define-common'
    961      allows Common symbols that are referenced from a shared library to
    962      be assigned addresses only in the main program.  This eliminates
    963      the unused duplicate space in the shared library, and also
    964      prevents any possible confusion over resolving to the wrong
    965      duplicate when there are many dynamic modules with specialized
    966      search paths for runtime symbol resolution.
    967 
    968 `--defsym=SYMBOL=EXPRESSION'
    969      Create a global symbol in the output file, containing the absolute
    970      address given by EXPRESSION.  You may use this option as many
    971      times as necessary to define multiple symbols in the command line.
    972      A limited form of arithmetic is supported for the EXPRESSION in
    973      this context: you may give a hexadecimal constant or the name of
    974      an existing symbol, or use `+' and `-' to add or subtract
    975      hexadecimal constants or symbols.  If you need more elaborate
    976      expressions, consider using the linker command language from a
    977      script (*note Assignment: Symbol Definitions: Assignments.).
    978      _Note:_ there should be no white space between SYMBOL, the equals
    979      sign ("<=>"), and EXPRESSION.
    980 
    981 `--demangle[=STYLE]'
    982 `--no-demangle'
    983      These options control whether to demangle symbol names in error
    984      messages and other output.  When the linker is told to demangle,
    985      it tries to present symbol names in a readable fashion: it strips
    986      leading underscores if they are used by the object file format,
    987      and converts C++ mangled symbol names into user readable names.
    988      Different compilers have different mangling styles.  The optional
    989      demangling style argument can be used to choose an appropriate
    990      demangling style for your compiler.  The linker will demangle by
    991      default unless the environment variable `COLLECT_NO_DEMANGLE' is
    992      set.  These options may be used to override the default.
    993 
    994 `-IFILE'
    995 `--dynamic-linker=FILE'
    996      Set the name of the dynamic linker.  This is only meaningful when
    997      generating dynamically linked ELF executables.  The default dynamic
    998      linker is normally correct; don't use this unless you know what
    999      you are doing.
   1000 
   1001 `--fatal-warnings'
   1002 `--no-fatal-warnings'
   1003      Treat all warnings as errors.  The default behaviour can be
   1004      restored with the option `--no-fatal-warnings'.
   1005 
   1006 `--force-exe-suffix'
   1007      Make sure that an output file has a .exe suffix.
   1008 
   1009      If a successfully built fully linked output file does not have a
   1010      `.exe' or `.dll' suffix, this option forces the linker to copy the
   1011      output file to one of the same name with a `.exe' suffix. This
   1012      option is useful when using unmodified Unix makefiles on a
   1013      Microsoft Windows host, since some versions of Windows won't run
   1014      an image unless it ends in a `.exe' suffix.
   1015 
   1016 `--gc-sections'
   1017 `--no-gc-sections'
   1018      Enable garbage collection of unused input sections.  It is ignored
   1019      on targets that do not support this option.  The default behaviour
   1020      (of not performing this garbage collection) can be restored by
   1021      specifying `--no-gc-sections' on the command line.
   1022 
   1023      `--gc-sections' decides which input sections are used by examining
   1024      symbols and relocations.  The section containing the entry symbol
   1025      and all sections containing symbols undefined on the command-line
   1026      will be kept, as will sections containing symbols referenced by
   1027      dynamic objects.  Note that when building shared libraries, the
   1028      linker must assume that any visible symbol is referenced.  Once
   1029      this initial set of sections has been determined, the linker
   1030      recursively marks as used any section referenced by their
   1031      relocations.  See `--entry' and `--undefined'.
   1032 
   1033      This option can be set when doing a partial link (enabled with
   1034      option `-r').  In this case the root of symbols kept must be
   1035      explicitly specified either by an `--entry' or `--undefined'
   1036      option or by a `ENTRY' command in the linker script.
   1037 
   1038 `--print-gc-sections'
   1039 `--no-print-gc-sections'
   1040      List all sections removed by garbage collection.  The listing is
   1041      printed on stderr.  This option is only effective if garbage
   1042      collection has been enabled via the `--gc-sections') option.  The
   1043      default behaviour (of not listing the sections that are removed)
   1044      can be restored by specifying `--no-print-gc-sections' on the
   1045      command line.
   1046 
   1047 `--help'
   1048      Print a summary of the command-line options on the standard output
   1049      and exit.
   1050 
   1051 `--target-help'
   1052      Print a summary of all target specific options on the standard
   1053      output and exit.
   1054 
   1055 `-Map=MAPFILE'
   1056      Print a link map to the file MAPFILE.  See the description of the
   1057      `-M' option, above.
   1058 
   1059 `--no-keep-memory'
   1060      `ld' normally optimizes for speed over memory usage by caching the
   1061      symbol tables of input files in memory.  This option tells `ld' to
   1062      instead optimize for memory usage, by rereading the symbol tables
   1063      as necessary.  This may be required if `ld' runs out of memory
   1064      space while linking a large executable.
   1065 
   1066 `--no-undefined'
   1067 `-z defs'
   1068      Report unresolved symbol references from regular object files.
   1069      This is done even if the linker is creating a non-symbolic shared
   1070      library.  The switch `--[no-]allow-shlib-undefined' controls the
   1071      behaviour for reporting unresolved references found in shared
   1072      libraries being linked in.
   1073 
   1074 `--allow-multiple-definition'
   1075 `-z muldefs'
   1076      Normally when a symbol is defined multiple times, the linker will
   1077      report a fatal error. These options allow multiple definitions and
   1078      the first definition will be used.
   1079 
   1080 `--allow-shlib-undefined'
   1081 `--no-allow-shlib-undefined'
   1082      Allows or disallows undefined symbols in shared libraries.  This
   1083      switch is similar to `--no-undefined' except that it determines
   1084      the behaviour when the undefined symbols are in a shared library
   1085      rather than a regular object file.  It does not affect how
   1086      undefined symbols in regular object files are handled.
   1087 
   1088      The default behaviour is to report errors for any undefined symbols
   1089      referenced in shared libraries if the linker is being used to
   1090      create an executable, but to allow them if the linker is being
   1091      used to create a shared library.
   1092 
   1093      The reasons for allowing undefined symbol references in shared
   1094      libraries specified at link time are that:
   1095 
   1096         * A shared library specified at link time may not be the same
   1097           as the one that is available at load time, so the symbol
   1098           might actually be resolvable at load time.
   1099 
   1100         * There are some operating systems, eg BeOS and HPPA, where
   1101           undefined symbols in shared libraries are normal.
   1102 
   1103           The BeOS kernel for example patches shared libraries at load
   1104           time to select whichever function is most appropriate for the
   1105           current architecture.  This is used, for example, to
   1106           dynamically select an appropriate memset function.
   1107 
   1108 `--no-undefined-version'
   1109      Normally when a symbol has an undefined version, the linker will
   1110      ignore it. This option disallows symbols with undefined version
   1111      and a fatal error will be issued instead.
   1112 
   1113 `--default-symver'
   1114      Create and use a default symbol version (the soname) for
   1115      unversioned exported symbols.
   1116 
   1117 `--default-imported-symver'
   1118      Create and use a default symbol version (the soname) for
   1119      unversioned imported symbols.
   1120 
   1121 `--no-warn-mismatch'
   1122      Normally `ld' will give an error if you try to link together input
   1123      files that are mismatched for some reason, perhaps because they
   1124      have been compiled for different processors or for different
   1125      endiannesses.  This option tells `ld' that it should silently
   1126      permit such possible errors.  This option should only be used with
   1127      care, in cases when you have taken some special action that
   1128      ensures that the linker errors are inappropriate.
   1129 
   1130 `--no-warn-search-mismatch'
   1131      Normally `ld' will give a warning if it finds an incompatible
   1132      library during a library search.  This option silences the warning.
   1133 
   1134 `--no-whole-archive'
   1135      Turn off the effect of the `--whole-archive' option for subsequent
   1136      archive files.
   1137 
   1138 `--noinhibit-exec'
   1139      Retain the executable output file whenever it is still usable.
   1140      Normally, the linker will not produce an output file if it
   1141      encounters errors during the link process; it exits without
   1142      writing an output file when it issues any error whatsoever.
   1143 
   1144 `-nostdlib'
   1145      Only search library directories explicitly specified on the
   1146      command line.  Library directories specified in linker scripts
   1147      (including linker scripts specified on the command line) are
   1148      ignored.
   1149 
   1150 `--oformat=OUTPUT-FORMAT'
   1151      `ld' may be configured to support more than one kind of object
   1152      file.  If your `ld' is configured this way, you can use the
   1153      `--oformat' option to specify the binary format for the output
   1154      object file.  Even when `ld' is configured to support alternative
   1155      object formats, you don't usually need to specify this, as `ld'
   1156      should be configured to produce as a default output format the most
   1157      usual format on each machine.  OUTPUT-FORMAT is a text string, the
   1158      name of a particular format supported by the BFD libraries.  (You
   1159      can list the available binary formats with `objdump -i'.)  The
   1160      script command `OUTPUT_FORMAT' can also specify the output format,
   1161      but this option overrides it.  *Note BFD::.
   1162 
   1163 `-pie'
   1164 `--pic-executable'
   1165      Create a position independent executable.  This is currently only
   1166      supported on ELF platforms.  Position independent executables are
   1167      similar to shared libraries in that they are relocated by the
   1168      dynamic linker to the virtual address the OS chooses for them
   1169      (which can vary between invocations).  Like normal dynamically
   1170      linked executables they can be executed and symbols defined in the
   1171      executable cannot be overridden by shared libraries.
   1172 
   1173 `-qmagic'
   1174      This option is ignored for Linux compatibility.
   1175 
   1176 `-Qy'
   1177      This option is ignored for SVR4 compatibility.
   1178 
   1179 `--relax'
   1180 `--no-relax'
   1181      An option with machine dependent effects.  This option is only
   1182      supported on a few targets.  *Note `ld' and the H8/300: H8/300.
   1183      *Note `ld' and the Intel 960 family: i960.  *Note `ld' and Xtensa
   1184      Processors: Xtensa.  *Note `ld' and the 68HC11 and 68HC12:
   1185      M68HC11/68HC12.  *Note `ld' and PowerPC 32-bit ELF Support:
   1186      PowerPC ELF32.
   1187 
   1188      On some platforms the `--relax' option performs target specific,
   1189      global optimizations that become possible when the linker resolves
   1190      addressing in the program, such as relaxing address modes,
   1191      synthesizing new instructions, selecting shorter version of current
   1192      instructions, and combinig constant values.
   1193 
   1194      On some platforms these link time global optimizations may make
   1195      symbolic debugging of the resulting executable impossible.  This
   1196      is known to be the case for the Matsushita MN10200 and MN10300
   1197      family of processors.
   1198 
   1199      On platforms where this is not supported, `--relax' is accepted,
   1200      but ignored.
   1201 
   1202      On platforms where `--relax' is accepted the option `--no-relax'
   1203      can be used to disable the feature.
   1204 
   1205 `--retain-symbols-file=FILENAME'
   1206      Retain _only_ the symbols listed in the file FILENAME, discarding
   1207      all others.  FILENAME is simply a flat file, with one symbol name
   1208      per line.  This option is especially useful in environments (such
   1209      as VxWorks) where a large global symbol table is accumulated
   1210      gradually, to conserve run-time memory.
   1211 
   1212      `--retain-symbols-file' does _not_ discard undefined symbols, or
   1213      symbols needed for relocations.
   1214 
   1215      You may only specify `--retain-symbols-file' once in the command
   1216      line.  It overrides `-s' and `-S'.
   1217 
   1218 `-rpath=DIR'
   1219      Add a directory to the runtime library search path.  This is used
   1220      when linking an ELF executable with shared objects.  All `-rpath'
   1221      arguments are concatenated and passed to the runtime linker, which
   1222      uses them to locate shared objects at runtime.  The `-rpath'
   1223      option is also used when locating shared objects which are needed
   1224      by shared objects explicitly included in the link; see the
   1225      description of the `-rpath-link' option.  If `-rpath' is not used
   1226      when linking an ELF executable, the contents of the environment
   1227      variable `LD_RUN_PATH' will be used if it is defined.
   1228 
   1229      The `-rpath' option may also be used on SunOS.  By default, on
   1230      SunOS, the linker will form a runtime search patch out of all the
   1231      `-L' options it is given.  If a `-rpath' option is used, the
   1232      runtime search path will be formed exclusively using the `-rpath'
   1233      options, ignoring the `-L' options.  This can be useful when using
   1234      gcc, which adds many `-L' options which may be on NFS mounted file
   1235      systems.
   1236 
   1237      For compatibility with other ELF linkers, if the `-R' option is
   1238      followed by a directory name, rather than a file name, it is
   1239      treated as the `-rpath' option.
   1240 
   1241 `-rpath-link=DIR'
   1242      When using ELF or SunOS, one shared library may require another.
   1243      This happens when an `ld -shared' link includes a shared library
   1244      as one of the input files.
   1245 
   1246      When the linker encounters such a dependency when doing a
   1247      non-shared, non-relocatable link, it will automatically try to
   1248      locate the required shared library and include it in the link, if
   1249      it is not included explicitly.  In such a case, the `-rpath-link'
   1250      option specifies the first set of directories to search.  The
   1251      `-rpath-link' option may specify a sequence of directory names
   1252      either by specifying a list of names separated by colons, or by
   1253      appearing multiple times.
   1254 
   1255      This option should be used with caution as it overrides the search
   1256      path that may have been hard compiled into a shared library. In
   1257      such a case it is possible to use unintentionally a different
   1258      search path than the runtime linker would do.
   1259 
   1260      The linker uses the following search paths to locate required
   1261      shared libraries:
   1262        1. Any directories specified by `-rpath-link' options.
   1263 
   1264        2. Any directories specified by `-rpath' options.  The difference
   1265           between `-rpath' and `-rpath-link' is that directories
   1266           specified by `-rpath' options are included in the executable
   1267           and used at runtime, whereas the `-rpath-link' option is only
   1268           effective at link time. Searching `-rpath' in this way is
   1269           only supported by native linkers and cross linkers which have
   1270           been configured with the `--with-sysroot' option.
   1271 
   1272        3. On an ELF system, for native linkers, if the `-rpath' and
   1273           `-rpath-link' options were not used, search the contents of
   1274           the environment variable `LD_RUN_PATH'.
   1275 
   1276        4. On SunOS, if the `-rpath' option was not used, search any
   1277           directories specified using `-L' options.
   1278 
   1279        5. For a native linker, the search the contents of the
   1280           environment variable `LD_LIBRARY_PATH'.
   1281 
   1282        6. For a native ELF linker, the directories in `DT_RUNPATH' or
   1283           `DT_RPATH' of a shared library are searched for shared
   1284           libraries needed by it. The `DT_RPATH' entries are ignored if
   1285           `DT_RUNPATH' entries exist.
   1286 
   1287        7. The default directories, normally `/lib' and `/usr/lib'.
   1288 
   1289        8. For a native linker on an ELF system, if the file
   1290           `/etc/ld.so.conf' exists, the list of directories found in
   1291           that file.
   1292 
   1293      If the required shared library is not found, the linker will issue
   1294      a warning and continue with the link.
   1295 
   1296 `-shared'
   1297 `-Bshareable'
   1298      Create a shared library.  This is currently only supported on ELF,
   1299      XCOFF and SunOS platforms.  On SunOS, the linker will
   1300      automatically create a shared library if the `-e' option is not
   1301      used and there are undefined symbols in the link.
   1302 
   1303 `--sort-common'
   1304 `--sort-common=ascending'
   1305 `--sort-common=descending'
   1306      This option tells `ld' to sort the common symbols by alignment in
   1307      ascending or descending order when it places them in the
   1308      appropriate output sections.  The symbol alignments considered are
   1309      sixteen-byte or larger, eight-byte, four-byte, two-byte, and
   1310      one-byte. This is to prevent gaps between symbols due to alignment
   1311      constraints.  If no sorting order is specified, then descending
   1312      order is assumed.
   1313 
   1314 `--sort-section=name'
   1315      This option will apply `SORT_BY_NAME' to all wildcard section
   1316      patterns in the linker script.
   1317 
   1318 `--sort-section=alignment'
   1319      This option will apply `SORT_BY_ALIGNMENT' to all wildcard section
   1320      patterns in the linker script.
   1321 
   1322 `--split-by-file[=SIZE]'
   1323      Similar to `--split-by-reloc' but creates a new output section for
   1324      each input file when SIZE is reached.  SIZE defaults to a size of
   1325      1 if not given.
   1326 
   1327 `--split-by-reloc[=COUNT]'
   1328      Tries to creates extra sections in the output file so that no
   1329      single output section in the file contains more than COUNT
   1330      relocations.  This is useful when generating huge relocatable
   1331      files for downloading into certain real time kernels with the COFF
   1332      object file format; since COFF cannot represent more than 65535
   1333      relocations in a single section.  Note that this will fail to work
   1334      with object file formats which do not support arbitrary sections.
   1335      The linker will not split up individual input sections for
   1336      redistribution, so if a single input section contains more than
   1337      COUNT relocations one output section will contain that many
   1338      relocations.  COUNT defaults to a value of 32768.
   1339 
   1340 `--stats'
   1341      Compute and display statistics about the operation of the linker,
   1342      such as execution time and memory usage.
   1343 
   1344 `--sysroot=DIRECTORY'
   1345      Use DIRECTORY as the location of the sysroot, overriding the
   1346      configure-time default.  This option is only supported by linkers
   1347      that were configured using `--with-sysroot'.
   1348 
   1349 `--traditional-format'
   1350      For some targets, the output of `ld' is different in some ways from
   1351      the output of some existing linker.  This switch requests `ld' to
   1352      use the traditional format instead.
   1353 
   1354      For example, on SunOS, `ld' combines duplicate entries in the
   1355      symbol string table.  This can reduce the size of an output file
   1356      with full debugging information by over 30 percent.
   1357      Unfortunately, the SunOS `dbx' program can not read the resulting
   1358      program (`gdb' has no trouble).  The `--traditional-format' switch
   1359      tells `ld' to not combine duplicate entries.
   1360 
   1361 `--section-start=SECTIONNAME=ORG'
   1362      Locate a section in the output file at the absolute address given
   1363      by ORG.  You may use this option as many times as necessary to
   1364      locate multiple sections in the command line.  ORG must be a
   1365      single hexadecimal integer; for compatibility with other linkers,
   1366      you may omit the leading `0x' usually associated with hexadecimal
   1367      values.  _Note:_ there should be no white space between
   1368      SECTIONNAME, the equals sign ("<=>"), and ORG.
   1369 
   1370 `-Tbss=ORG'
   1371 `-Tdata=ORG'
   1372 `-Ttext=ORG'
   1373      Same as `--section-start', with `.bss', `.data' or `.text' as the
   1374      SECTIONNAME.
   1375 
   1376 `-Ttext-segment=ORG'
   1377      When creating an ELF executable or shared object, it will set the
   1378      address of the first byte of the text segment.
   1379 
   1380 `--unresolved-symbols=METHOD'
   1381      Determine how to handle unresolved symbols.  There are four
   1382      possible values for `method':
   1383 
   1384     `ignore-all'
   1385           Do not report any unresolved symbols.
   1386 
   1387     `report-all'
   1388           Report all unresolved symbols.  This is the default.
   1389 
   1390     `ignore-in-object-files'
   1391           Report unresolved symbols that are contained in shared
   1392           libraries, but ignore them if they come from regular object
   1393           files.
   1394 
   1395     `ignore-in-shared-libs'
   1396           Report unresolved symbols that come from regular object
   1397           files, but ignore them if they come from shared libraries.
   1398           This can be useful when creating a dynamic binary and it is
   1399           known that all the shared libraries that it should be
   1400           referencing are included on the linker's command line.
   1401 
   1402      The behaviour for shared libraries on their own can also be
   1403      controlled by the `--[no-]allow-shlib-undefined' option.
   1404 
   1405      Normally the linker will generate an error message for each
   1406      reported unresolved symbol but the option
   1407      `--warn-unresolved-symbols' can change this to a warning.
   1408 
   1409 `--dll-verbose'
   1410 `--verbose'
   1411      Display the version number for `ld' and list the linker emulations
   1412      supported.  Display which input files can and cannot be opened.
   1413      Display the linker script being used by the linker.
   1414 
   1415 `--version-script=VERSION-SCRIPTFILE'
   1416      Specify the name of a version script to the linker.  This is
   1417      typically used when creating shared libraries to specify
   1418      additional information about the version hierarchy for the library
   1419      being created.  This option is only fully supported on ELF
   1420      platforms which support shared libraries; see *note VERSION::.  It
   1421      is partially supported on PE platforms, which can use version
   1422      scripts to filter symbol visibility in auto-export mode: any
   1423      symbols marked `local' in the version script will not be exported.
   1424      *Note WIN32::.
   1425 
   1426 `--warn-common'
   1427      Warn when a common symbol is combined with another common symbol
   1428      or with a symbol definition.  Unix linkers allow this somewhat
   1429      sloppy practise, but linkers on some other operating systems do
   1430      not.  This option allows you to find potential problems from
   1431      combining global symbols.  Unfortunately, some C libraries use
   1432      this practise, so you may get some warnings about symbols in the
   1433      libraries as well as in your programs.
   1434 
   1435      There are three kinds of global symbols, illustrated here by C
   1436      examples:
   1437 
   1438     `int i = 1;'
   1439           A definition, which goes in the initialized data section of
   1440           the output file.
   1441 
   1442     `extern int i;'
   1443           An undefined reference, which does not allocate space.  There
   1444           must be either a definition or a common symbol for the
   1445           variable somewhere.
   1446 
   1447     `int i;'
   1448           A common symbol.  If there are only (one or more) common
   1449           symbols for a variable, it goes in the uninitialized data
   1450           area of the output file.  The linker merges multiple common
   1451           symbols for the same variable into a single symbol.  If they
   1452           are of different sizes, it picks the largest size.  The
   1453           linker turns a common symbol into a declaration, if there is
   1454           a definition of the same variable.
   1455 
   1456      The `--warn-common' option can produce five kinds of warnings.
   1457      Each warning consists of a pair of lines: the first describes the
   1458      symbol just encountered, and the second describes the previous
   1459      symbol encountered with the same name.  One or both of the two
   1460      symbols will be a common symbol.
   1461 
   1462        1. Turning a common symbol into a reference, because there is
   1463           already a definition for the symbol.
   1464                FILE(SECTION): warning: common of `SYMBOL'
   1465                   overridden by definition
   1466                FILE(SECTION): warning: defined here
   1467 
   1468        2. Turning a common symbol into a reference, because a later
   1469           definition for the symbol is encountered.  This is the same
   1470           as the previous case, except that the symbols are encountered
   1471           in a different order.
   1472                FILE(SECTION): warning: definition of `SYMBOL'
   1473                   overriding common
   1474                FILE(SECTION): warning: common is here
   1475 
   1476        3. Merging a common symbol with a previous same-sized common
   1477           symbol.
   1478                FILE(SECTION): warning: multiple common
   1479                   of `SYMBOL'
   1480                FILE(SECTION): warning: previous common is here
   1481 
   1482        4. Merging a common symbol with a previous larger common symbol.
   1483                FILE(SECTION): warning: common of `SYMBOL'
   1484                   overridden by larger common
   1485                FILE(SECTION): warning: larger common is here
   1486 
   1487        5. Merging a common symbol with a previous smaller common
   1488           symbol.  This is the same as the previous case, except that
   1489           the symbols are encountered in a different order.
   1490                FILE(SECTION): warning: common of `SYMBOL'
   1491                   overriding smaller common
   1492                FILE(SECTION): warning: smaller common is here
   1493 
   1494 `--warn-constructors'
   1495      Warn if any global constructors are used.  This is only useful for
   1496      a few object file formats.  For formats like COFF or ELF, the
   1497      linker can not detect the use of global constructors.
   1498 
   1499 `--warn-multiple-gp'
   1500      Warn if multiple global pointer values are required in the output
   1501      file.  This is only meaningful for certain processors, such as the
   1502      Alpha.  Specifically, some processors put large-valued constants
   1503      in a special section.  A special register (the global pointer)
   1504      points into the middle of this section, so that constants can be
   1505      loaded efficiently via a base-register relative addressing mode.
   1506      Since the offset in base-register relative mode is fixed and
   1507      relatively small (e.g., 16 bits), this limits the maximum size of
   1508      the constant pool.  Thus, in large programs, it is often necessary
   1509      to use multiple global pointer values in order to be able to
   1510      address all possible constants.  This option causes a warning to
   1511      be issued whenever this case occurs.
   1512 
   1513 `--warn-once'
   1514      Only warn once for each undefined symbol, rather than once per
   1515      module which refers to it.
   1516 
   1517 `--warn-section-align'
   1518      Warn if the address of an output section is changed because of
   1519      alignment.  Typically, the alignment will be set by an input
   1520      section.  The address will only be changed if it not explicitly
   1521      specified; that is, if the `SECTIONS' command does not specify a
   1522      start address for the section (*note SECTIONS::).
   1523 
   1524 `--warn-shared-textrel'
   1525      Warn if the linker adds a DT_TEXTREL to a shared object.
   1526 
   1527 `--warn-alternate-em'
   1528      Warn if an object has alternate ELF machine code.
   1529 
   1530 `--warn-unresolved-symbols'
   1531      If the linker is going to report an unresolved symbol (see the
   1532      option `--unresolved-symbols') it will normally generate an error.
   1533      This option makes it generate a warning instead.
   1534 
   1535 `--error-unresolved-symbols'
   1536      This restores the linker's default behaviour of generating errors
   1537      when it is reporting unresolved symbols.
   1538 
   1539 `--whole-archive'
   1540      For each archive mentioned on the command line after the
   1541      `--whole-archive' option, include every object file in the archive
   1542      in the link, rather than searching the archive for the required
   1543      object files.  This is normally used to turn an archive file into
   1544      a shared library, forcing every object to be included in the
   1545      resulting shared library.  This option may be used more than once.
   1546 
   1547      Two notes when using this option from gcc: First, gcc doesn't know
   1548      about this option, so you have to use `-Wl,-whole-archive'.
   1549      Second, don't forget to use `-Wl,-no-whole-archive' after your
   1550      list of archives, because gcc will add its own list of archives to
   1551      your link and you may not want this flag to affect those as well.
   1552 
   1553 `--wrap=SYMBOL'
   1554      Use a wrapper function for SYMBOL.  Any undefined reference to
   1555      SYMBOL will be resolved to `__wrap_SYMBOL'.  Any undefined
   1556      reference to `__real_SYMBOL' will be resolved to SYMBOL.
   1557 
   1558      This can be used to provide a wrapper for a system function.  The
   1559      wrapper function should be called `__wrap_SYMBOL'.  If it wishes
   1560      to call the system function, it should call `__real_SYMBOL'.
   1561 
   1562      Here is a trivial example:
   1563 
   1564           void *
   1565           __wrap_malloc (size_t c)
   1566           {
   1567             printf ("malloc called with %zu\n", c);
   1568             return __real_malloc (c);
   1569           }
   1570 
   1571      If you link other code with this file using `--wrap malloc', then
   1572      all calls to `malloc' will call the function `__wrap_malloc'
   1573      instead.  The call to `__real_malloc' in `__wrap_malloc' will call
   1574      the real `malloc' function.
   1575 
   1576      You may wish to provide a `__real_malloc' function as well, so that
   1577      links without the `--wrap' option will succeed.  If you do this,
   1578      you should not put the definition of `__real_malloc' in the same
   1579      file as `__wrap_malloc'; if you do, the assembler may resolve the
   1580      call before the linker has a chance to wrap it to `malloc'.
   1581 
   1582 `--eh-frame-hdr'
   1583      Request creation of `.eh_frame_hdr' section and ELF
   1584      `PT_GNU_EH_FRAME' segment header.
   1585 
   1586 `--enable-new-dtags'
   1587 `--disable-new-dtags'
   1588      This linker can create the new dynamic tags in ELF. But the older
   1589      ELF systems may not understand them. If you specify
   1590      `--enable-new-dtags', the dynamic tags will be created as needed.
   1591      If you specify `--disable-new-dtags', no new dynamic tags will be
   1592      created. By default, the new dynamic tags are not created. Note
   1593      that those options are only available for ELF systems.
   1594 
   1595 `--hash-size=NUMBER'
   1596      Set the default size of the linker's hash tables to a prime number
   1597      close to NUMBER.  Increasing this value can reduce the length of
   1598      time it takes the linker to perform its tasks, at the expense of
   1599      increasing the linker's memory requirements.  Similarly reducing
   1600      this value can reduce the memory requirements at the expense of
   1601      speed.
   1602 
   1603 `--hash-style=STYLE'
   1604      Set the type of linker's hash table(s).  STYLE can be either
   1605      `sysv' for classic ELF `.hash' section, `gnu' for new style GNU
   1606      `.gnu.hash' section or `both' for both the classic ELF `.hash' and
   1607      new style GNU `.gnu.hash' hash tables.  The default is `sysv'.
   1608 
   1609 `--reduce-memory-overheads'
   1610      This option reduces memory requirements at ld runtime, at the
   1611      expense of linking speed.  This was introduced to select the old
   1612      O(n^2) algorithm for link map file generation, rather than the new
   1613      O(n) algorithm which uses about 40% more memory for symbol storage.
   1614 
   1615      Another effect of the switch is to set the default hash table size
   1616      to 1021, which again saves memory at the cost of lengthening the
   1617      linker's run time.  This is not done however if the `--hash-size'
   1618      switch has been used.
   1619 
   1620      The `--reduce-memory-overheads' switch may be also be used to
   1621      enable other tradeoffs in future versions of the linker.
   1622 
   1623 `--build-id'
   1624 `--build-id=STYLE'
   1625      Request creation of `.note.gnu.build-id' ELF note section.  The
   1626      contents of the note are unique bits identifying this linked file.
   1627      STYLE can be `uuid' to use 128 random bits, `sha1' to use a
   1628      160-bit SHA1 hash on the normative parts of the output contents,
   1629      `md5' to use a 128-bit MD5 hash on the normative parts of the
   1630      output contents, or `0xHEXSTRING' to use a chosen bit string
   1631      specified as an even number of hexadecimal digits (`-' and `:'
   1632      characters between digit pairs are ignored).  If STYLE is omitted,
   1633      `sha1' is used.
   1634 
   1635      The `md5' and `sha1' styles produces an identifier that is always
   1636      the same in an identical output file, but will be unique among all
   1637      nonidentical output files.  It is not intended to be compared as a
   1638      checksum for the file's contents.  A linked file may be changed
   1639      later by other tools, but the build ID bit string identifying the
   1640      original linked file does not change.
   1641 
   1642      Passing `none' for STYLE disables the setting from any
   1643      `--build-id' options earlier on the command line.
   1644 
   1645 2.1.1 Options Specific to i386 PE Targets
   1646 -----------------------------------------
   1647 
   1648 The i386 PE linker supports the `-shared' option, which causes the
   1649 output to be a dynamically linked library (DLL) instead of a normal
   1650 executable.  You should name the output `*.dll' when you use this
   1651 option.  In addition, the linker fully supports the standard `*.def'
   1652 files, which may be specified on the linker command line like an object
   1653 file (in fact, it should precede archives it exports symbols from, to
   1654 ensure that they get linked in, just like a normal object file).
   1655 
   1656    In addition to the options common to all targets, the i386 PE linker
   1657 support additional command line options that are specific to the i386
   1658 PE target.  Options that take values may be separated from their values
   1659 by either a space or an equals sign.
   1660 
   1661 `--add-stdcall-alias'
   1662      If given, symbols with a stdcall suffix (@NN) will be exported
   1663      as-is and also with the suffix stripped.  [This option is specific
   1664      to the i386 PE targeted port of the linker]
   1665 
   1666 `--base-file FILE'
   1667      Use FILE as the name of a file in which to save the base addresses
   1668      of all the relocations needed for generating DLLs with `dlltool'.
   1669      [This is an i386 PE specific option]
   1670 
   1671 `--dll'
   1672      Create a DLL instead of a regular executable.  You may also use
   1673      `-shared' or specify a `LIBRARY' in a given `.def' file.  [This
   1674      option is specific to the i386 PE targeted port of the linker]
   1675 
   1676 `--enable-long-section-names'
   1677 `--disable-long-section-names'
   1678      The PE variants of the Coff object format add an extension that
   1679      permits the use of section names longer than eight characters, the
   1680      normal limit for Coff.  By default, these names are only allowed
   1681      in object files, as fully-linked executable images do not carry
   1682      the Coff string table required to support the longer names.  As a
   1683      GNU extension, it is possible to allow their use in executable
   1684      images as well, or to (probably pointlessly!)  disallow it in
   1685      object files, by using these two options.  Executable images
   1686      generated with these long section names are slightly non-standard,
   1687      carrying as they do a string table, and may generate confusing
   1688      output when examined with non-GNU PE-aware tools, such as file
   1689      viewers and dumpers.  However, GDB relies on the use of PE long
   1690      section names to find Dwarf-2 debug information sections in an
   1691      executable image at runtime, and so if neither option is specified
   1692      on the command-line, `ld' will enable long section names,
   1693      overriding the default and technically correct behaviour, when it
   1694      finds the presence of debug information while linking an executable
   1695      image and not stripping symbols.  [This option is valid for all PE
   1696      targeted ports of the linker]
   1697 
   1698 `--enable-stdcall-fixup'
   1699 `--disable-stdcall-fixup'
   1700      If the link finds a symbol that it cannot resolve, it will attempt
   1701      to do "fuzzy linking" by looking for another defined symbol that
   1702      differs only in the format of the symbol name (cdecl vs stdcall)
   1703      and will resolve that symbol by linking to the match.  For
   1704      example, the undefined symbol `_foo' might be linked to the
   1705      function `_foo@12', or the undefined symbol `_bar@16' might be
   1706      linked to the function `_bar'.  When the linker does this, it
   1707      prints a warning, since it normally should have failed to link,
   1708      but sometimes import libraries generated from third-party dlls may
   1709      need this feature to be usable.  If you specify
   1710      `--enable-stdcall-fixup', this feature is fully enabled and
   1711      warnings are not printed.  If you specify
   1712      `--disable-stdcall-fixup', this feature is disabled and such
   1713      mismatches are considered to be errors.  [This option is specific
   1714      to the i386 PE targeted port of the linker]
   1715 
   1716 `--leading-underscore'
   1717 `--no-leading-underscore'
   1718      For most targets default symbol-prefix is an underscore and is
   1719      defined in target's description. By this option it is possible to
   1720      disable/enable the default underscore symbol-prefix.
   1721 
   1722 `--export-all-symbols'
   1723      If given, all global symbols in the objects used to build a DLL
   1724      will be exported by the DLL.  Note that this is the default if
   1725      there otherwise wouldn't be any exported symbols.  When symbols are
   1726      explicitly exported via DEF files or implicitly exported via
   1727      function attributes, the default is to not export anything else
   1728      unless this option is given.  Note that the symbols `DllMain@12',
   1729      `DllEntryPoint@0', `DllMainCRTStartup@12', and `impure_ptr' will
   1730      not be automatically exported.  Also, symbols imported from other
   1731      DLLs will not be re-exported, nor will symbols specifying the
   1732      DLL's internal layout such as those beginning with `_head_' or
   1733      ending with `_iname'.  In addition, no symbols from `libgcc',
   1734      `libstd++', `libmingw32', or `crtX.o' will be exported.  Symbols
   1735      whose names begin with `__rtti_' or `__builtin_' will not be
   1736      exported, to help with C++ DLLs.  Finally, there is an extensive
   1737      list of cygwin-private symbols that are not exported (obviously,
   1738      this applies on when building DLLs for cygwin targets).  These
   1739      cygwin-excludes are: `_cygwin_dll_entry@12',
   1740      `_cygwin_crt0_common@8', `_cygwin_noncygwin_dll_entry@12',
   1741      `_fmode', `_impure_ptr', `cygwin_attach_dll', `cygwin_premain0',
   1742      `cygwin_premain1', `cygwin_premain2', `cygwin_premain3', and
   1743      `environ'.  [This option is specific to the i386 PE targeted port
   1744      of the linker]
   1745 
   1746 `--exclude-symbols SYMBOL,SYMBOL,...'
   1747      Specifies a list of symbols which should not be automatically
   1748      exported.  The symbol names may be delimited by commas or colons.
   1749      [This option is specific to the i386 PE targeted port of the
   1750      linker]
   1751 
   1752 `--exclude-all-symbols'
   1753      Specifies no symbols should be automatically exported.  [This
   1754      option is specific to the i386 PE targeted port of the linker]
   1755 
   1756 `--file-alignment'
   1757      Specify the file alignment.  Sections in the file will always
   1758      begin at file offsets which are multiples of this number.  This
   1759      defaults to 512.  [This option is specific to the i386 PE targeted
   1760      port of the linker]
   1761 
   1762 `--heap RESERVE'
   1763 `--heap RESERVE,COMMIT'
   1764      Specify the number of bytes of memory to reserve (and optionally
   1765      commit) to be used as heap for this program.  The default is 1Mb
   1766      reserved, 4K committed.  [This option is specific to the i386 PE
   1767      targeted port of the linker]
   1768 
   1769 `--image-base VALUE'
   1770      Use VALUE as the base address of your program or dll.  This is the
   1771      lowest memory location that will be used when your program or dll
   1772      is loaded.  To reduce the need to relocate and improve performance
   1773      of your dlls, each should have a unique base address and not
   1774      overlap any other dlls.  The default is 0x400000 for executables,
   1775      and 0x10000000 for dlls.  [This option is specific to the i386 PE
   1776      targeted port of the linker]
   1777 
   1778 `--kill-at'
   1779      If given, the stdcall suffixes (@NN) will be stripped from symbols
   1780      before they are exported.  [This option is specific to the i386 PE
   1781      targeted port of the linker]
   1782 
   1783 `--large-address-aware'
   1784      If given, the appropriate bit in the "Characteristics" field of
   1785      the COFF header is set to indicate that this executable supports
   1786      virtual addresses greater than 2 gigabytes.  This should be used
   1787      in conjunction with the /3GB or /USERVA=VALUE megabytes switch in
   1788      the "[operating systems]" section of the BOOT.INI.  Otherwise,
   1789      this bit has no effect.  [This option is specific to PE targeted
   1790      ports of the linker]
   1791 
   1792 `--major-image-version VALUE'
   1793      Sets the major number of the "image version".  Defaults to 1.
   1794      [This option is specific to the i386 PE targeted port of the
   1795      linker]
   1796 
   1797 `--major-os-version VALUE'
   1798      Sets the major number of the "os version".  Defaults to 4.  [This
   1799      option is specific to the i386 PE targeted port of the linker]
   1800 
   1801 `--major-subsystem-version VALUE'
   1802      Sets the major number of the "subsystem version".  Defaults to 4.
   1803      [This option is specific to the i386 PE targeted port of the
   1804      linker]
   1805 
   1806 `--minor-image-version VALUE'
   1807      Sets the minor number of the "image version".  Defaults to 0.
   1808      [This option is specific to the i386 PE targeted port of the
   1809      linker]
   1810 
   1811 `--minor-os-version VALUE'
   1812      Sets the minor number of the "os version".  Defaults to 0.  [This
   1813      option is specific to the i386 PE targeted port of the linker]
   1814 
   1815 `--minor-subsystem-version VALUE'
   1816      Sets the minor number of the "subsystem version".  Defaults to 0.
   1817      [This option is specific to the i386 PE targeted port of the
   1818      linker]
   1819 
   1820 `--output-def FILE'
   1821      The linker will create the file FILE which will contain a DEF file
   1822      corresponding to the DLL the linker is generating.  This DEF file
   1823      (which should be called `*.def') may be used to create an import
   1824      library with `dlltool' or may be used as a reference to
   1825      automatically or implicitly exported symbols.  [This option is
   1826      specific to the i386 PE targeted port of the linker]
   1827 
   1828 `--out-implib FILE'
   1829      The linker will create the file FILE which will contain an import
   1830      lib corresponding to the DLL the linker is generating. This import
   1831      lib (which should be called `*.dll.a' or `*.a' may be used to link
   1832      clients against the generated DLL; this behaviour makes it
   1833      possible to skip a separate `dlltool' import library creation step.
   1834      [This option is specific to the i386 PE targeted port of the
   1835      linker]
   1836 
   1837 `--enable-auto-image-base'
   1838      Automatically choose the image base for DLLs, unless one is
   1839      specified using the `--image-base' argument.  By using a hash
   1840      generated from the dllname to create unique image bases for each
   1841      DLL, in-memory collisions and relocations which can delay program
   1842      execution are avoided.  [This option is specific to the i386 PE
   1843      targeted port of the linker]
   1844 
   1845 `--disable-auto-image-base'
   1846      Do not automatically generate a unique image base.  If there is no
   1847      user-specified image base (`--image-base') then use the platform
   1848      default.  [This option is specific to the i386 PE targeted port of
   1849      the linker]
   1850 
   1851 `--dll-search-prefix STRING'
   1852      When linking dynamically to a dll without an import library,
   1853      search for `<string><basename>.dll' in preference to
   1854      `lib<basename>.dll'. This behaviour allows easy distinction
   1855      between DLLs built for the various "subplatforms": native, cygwin,
   1856      uwin, pw, etc.  For instance, cygwin DLLs typically use
   1857      `--dll-search-prefix=cyg'.  [This option is specific to the i386
   1858      PE targeted port of the linker]
   1859 
   1860 `--enable-auto-import'
   1861      Do sophisticated linking of `_symbol' to `__imp__symbol' for DATA
   1862      imports from DLLs, and create the necessary thunking symbols when
   1863      building the import libraries with those DATA exports. Note: Use
   1864      of the 'auto-import' extension will cause the text section of the
   1865      image file to be made writable. This does not conform to the
   1866      PE-COFF format specification published by Microsoft.
   1867 
   1868      Note - use of the 'auto-import' extension will also cause read only
   1869      data which would normally be placed into the .rdata section to be
   1870      placed into the .data section instead.  This is in order to work
   1871      around a problem with consts that is described here:
   1872      http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
   1873 
   1874      Using 'auto-import' generally will 'just work' - but sometimes you
   1875      may see this message:
   1876 
   1877      "variable '<var>' can't be auto-imported. Please read the
   1878      documentation for ld's `--enable-auto-import' for details."
   1879 
   1880      This message occurs when some (sub)expression accesses an address
   1881      ultimately given by the sum of two constants (Win32 import tables
   1882      only allow one).  Instances where this may occur include accesses
   1883      to member fields of struct variables imported from a DLL, as well
   1884      as using a constant index into an array variable imported from a
   1885      DLL.  Any multiword variable (arrays, structs, long long, etc) may
   1886      trigger this error condition.  However, regardless of the exact
   1887      data type of the offending exported variable, ld will always
   1888      detect it, issue the warning, and exit.
   1889 
   1890      There are several ways to address this difficulty, regardless of
   1891      the data type of the exported variable:
   1892 
   1893      One way is to use -enable-runtime-pseudo-reloc switch. This leaves
   1894      the task of adjusting references in your client code for runtime
   1895      environment, so this method works only when runtime environment
   1896      supports this feature.
   1897 
   1898      A second solution is to force one of the 'constants' to be a
   1899      variable - that is, unknown and un-optimizable at compile time.
   1900      For arrays, there are two possibilities: a) make the indexee (the
   1901      array's address) a variable, or b) make the 'constant' index a
   1902      variable.  Thus:
   1903 
   1904           extern type extern_array[];
   1905           extern_array[1] -->
   1906              { volatile type *t=extern_array; t[1] }
   1907 
   1908      or
   1909 
   1910           extern type extern_array[];
   1911           extern_array[1] -->
   1912              { volatile int t=1; extern_array[t] }
   1913 
   1914      For structs (and most other multiword data types) the only option
   1915      is to make the struct itself (or the long long, or the ...)
   1916      variable:
   1917 
   1918           extern struct s extern_struct;
   1919           extern_struct.field -->
   1920              { volatile struct s *t=&extern_struct; t->field }
   1921 
   1922      or
   1923 
   1924           extern long long extern_ll;
   1925           extern_ll -->
   1926             { volatile long long * local_ll=&extern_ll; *local_ll }
   1927 
   1928      A third method of dealing with this difficulty is to abandon
   1929      'auto-import' for the offending symbol and mark it with
   1930      `__declspec(dllimport)'.  However, in practise that requires using
   1931      compile-time #defines to indicate whether you are building a DLL,
   1932      building client code that will link to the DLL, or merely
   1933      building/linking to a static library.   In making the choice
   1934      between the various methods of resolving the 'direct address with
   1935      constant offset' problem, you should consider typical real-world
   1936      usage:
   1937 
   1938      Original:
   1939           --foo.h
   1940           extern int arr[];
   1941           --foo.c
   1942           #include "foo.h"
   1943           void main(int argc, char **argv){
   1944             printf("%d\n",arr[1]);
   1945           }
   1946 
   1947      Solution 1:
   1948           --foo.h
   1949           extern int arr[];
   1950           --foo.c
   1951           #include "foo.h"
   1952           void main(int argc, char **argv){
   1953             /* This workaround is for win32 and cygwin; do not "optimize" */
   1954             volatile int *parr = arr;
   1955             printf("%d\n",parr[1]);
   1956           }
   1957 
   1958      Solution 2:
   1959           --foo.h
   1960           /* Note: auto-export is assumed (no __declspec(dllexport)) */
   1961           #if (defined(_WIN32) || defined(__CYGWIN__)) && \
   1962             !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
   1963           #define FOO_IMPORT __declspec(dllimport)
   1964           #else
   1965           #define FOO_IMPORT
   1966           #endif
   1967           extern FOO_IMPORT int arr[];
   1968           --foo.c
   1969           #include "foo.h"
   1970           void main(int argc, char **argv){
   1971             printf("%d\n",arr[1]);
   1972           }
   1973 
   1974      A fourth way to avoid this problem is to re-code your library to
   1975      use a functional interface rather than a data interface for the
   1976      offending variables (e.g. set_foo() and get_foo() accessor
   1977      functions).  [This option is specific to the i386 PE targeted port
   1978      of the linker]
   1979 
   1980 `--disable-auto-import'
   1981      Do not attempt to do sophisticated linking of `_symbol' to
   1982      `__imp__symbol' for DATA imports from DLLs.  [This option is
   1983      specific to the i386 PE targeted port of the linker]
   1984 
   1985 `--enable-runtime-pseudo-reloc'
   1986      If your code contains expressions described in -enable-auto-import
   1987      section, that is, DATA imports from DLL with non-zero offset, this
   1988      switch will create a vector of 'runtime pseudo relocations' which
   1989      can be used by runtime environment to adjust references to such
   1990      data in your client code.  [This option is specific to the i386 PE
   1991      targeted port of the linker]
   1992 
   1993 `--disable-runtime-pseudo-reloc'
   1994      Do not create pseudo relocations for non-zero offset DATA imports
   1995      from DLLs.  This is the default.  [This option is specific to the
   1996      i386 PE targeted port of the linker]
   1997 
   1998 `--enable-extra-pe-debug'
   1999      Show additional debug info related to auto-import symbol thunking.
   2000      [This option is specific to the i386 PE targeted port of the
   2001      linker]
   2002 
   2003 `--section-alignment'
   2004      Sets the section alignment.  Sections in memory will always begin
   2005      at addresses which are a multiple of this number.  Defaults to
   2006      0x1000.  [This option is specific to the i386 PE targeted port of
   2007      the linker]
   2008 
   2009 `--stack RESERVE'
   2010 `--stack RESERVE,COMMIT'
   2011      Specify the number of bytes of memory to reserve (and optionally
   2012      commit) to be used as stack for this program.  The default is 2Mb
   2013      reserved, 4K committed.  [This option is specific to the i386 PE
   2014      targeted port of the linker]
   2015 
   2016 `--subsystem WHICH'
   2017 `--subsystem WHICH:MAJOR'
   2018 `--subsystem WHICH:MAJOR.MINOR'
   2019      Specifies the subsystem under which your program will execute.  The
   2020      legal values for WHICH are `native', `windows', `console',
   2021      `posix', and `xbox'.  You may optionally set the subsystem version
   2022      also.  Numeric values are also accepted for WHICH.  [This option
   2023      is specific to the i386 PE targeted port of the linker]
   2024 
   2025      The following options set flags in the `DllCharacteristics' field
   2026      of the PE file header: [These options are specific to PE targeted
   2027      ports of the linker]
   2028 
   2029 `--dynamicbase'
   2030      The image base address may be relocated using address space layout
   2031      randomization (ASLR).  This feature was introduced with MS Windows
   2032      Vista for i386 PE targets.
   2033 
   2034 `--forceinteg'
   2035      Code integrity checks are enforced.
   2036 
   2037 `--nxcompat'
   2038      The image is compatible with the Data Execution Prevention.  This
   2039      feature was introduced with MS Windows XP SP2 for i386 PE targets.
   2040 
   2041 `--no-isolation'
   2042      Although the image understands isolation, do not isolate the image.
   2043 
   2044 `--no-seh'
   2045      The image does not use SEH. No SE handler may be called from this
   2046      image.
   2047 
   2048 `--no-bind'
   2049      Do not bind this image.
   2050 
   2051 `--wdmdriver'
   2052      The driver uses the MS Windows Driver Model.
   2053 
   2054 `--tsaware'
   2055      The image is Terminal Server aware.
   2056 
   2057 
   2058 2.1.2 Options specific to Motorola 68HC11 and 68HC12 targets
   2059 ------------------------------------------------------------
   2060 
   2061 The 68HC11 and 68HC12 linkers support specific options to control the
   2062 memory bank switching mapping and trampoline code generation.
   2063 
   2064 `--no-trampoline'
   2065      This option disables the generation of trampoline. By default a
   2066      trampoline is generated for each far function which is called
   2067      using a `jsr' instruction (this happens when a pointer to a far
   2068      function is taken).
   2069 
   2070 `--bank-window NAME'
   2071      This option indicates to the linker the name of the memory region
   2072      in the `MEMORY' specification that describes the memory bank
   2073      window.  The definition of such region is then used by the linker
   2074      to compute paging and addresses within the memory window.
   2075 
   2076 
   2077 2.1.3 Options specific to Motorola 68K target
   2078 ---------------------------------------------
   2079 
   2080 The following options are supported to control handling of GOT
   2081 generation when linking for 68K targets.
   2082 
   2083 `--got=TYPE'
   2084      This option tells the linker which GOT generation scheme to use.
   2085      TYPE should be one of `single', `negative', `multigot' or
   2086      `target'.  For more information refer to the Info entry for `ld'.
   2087 
   2088 
   2089 
   2090 File: ld.info,  Node: Environment,  Prev: Options,  Up: Invocation
   2091 
   2092 2.2 Environment Variables
   2093 =========================
   2094 
   2095 You can change the behaviour of `ld' with the environment variables
   2096 `GNUTARGET', `LDEMULATION' and `COLLECT_NO_DEMANGLE'.
   2097 
   2098    `GNUTARGET' determines the input-file object format if you don't use
   2099 `-b' (or its synonym `--format').  Its value should be one of the BFD
   2100 names for an input format (*note BFD::).  If there is no `GNUTARGET' in
   2101 the environment, `ld' uses the natural format of the target. If
   2102 `GNUTARGET' is set to `default' then BFD attempts to discover the input
   2103 format by examining binary input files; this method often succeeds, but
   2104 there are potential ambiguities, since there is no method of ensuring
   2105 that the magic number used to specify object-file formats is unique.
   2106 However, the configuration procedure for BFD on each system places the
   2107 conventional format for that system first in the search-list, so
   2108 ambiguities are resolved in favor of convention.
   2109 
   2110    `LDEMULATION' determines the default emulation if you don't use the
   2111 `-m' option.  The emulation can affect various aspects of linker
   2112 behaviour, particularly the default linker script.  You can list the
   2113 available emulations with the `--verbose' or `-V' options.  If the `-m'
   2114 option is not used, and the `LDEMULATION' environment variable is not
   2115 defined, the default emulation depends upon how the linker was
   2116 configured.
   2117 
   2118    Normally, the linker will default to demangling symbols.  However, if
   2119 `COLLECT_NO_DEMANGLE' is set in the environment, then it will default
   2120 to not demangling symbols.  This environment variable is used in a
   2121 similar fashion by the `gcc' linker wrapper program.  The default may
   2122 be overridden by the `--demangle' and `--no-demangle' options.
   2123 
   2124 
   2125 File: ld.info,  Node: Scripts,  Next: Machine Dependent,  Prev: Invocation,  Up: Top
   2126 
   2127 3 Linker Scripts
   2128 ****************
   2129 
   2130 Every link is controlled by a "linker script".  This script is written
   2131 in the linker command language.
   2132 
   2133    The main purpose of the linker script is to describe how the
   2134 sections in the input files should be mapped into the output file, and
   2135 to control the memory layout of the output file.  Most linker scripts
   2136 do nothing more than this.  However, when necessary, the linker script
   2137 can also direct the linker to perform many other operations, using the
   2138 commands described below.
   2139 
   2140    The linker always uses a linker script.  If you do not supply one
   2141 yourself, the linker will use a default script that is compiled into the
   2142 linker executable.  You can use the `--verbose' command line option to
   2143 display the default linker script.  Certain command line options, such
   2144 as `-r' or `-N', will affect the default linker script.
   2145 
   2146    You may supply your own linker script by using the `-T' command line
   2147 option.  When you do this, your linker script will replace the default
   2148 linker script.
   2149 
   2150    You may also use linker scripts implicitly by naming them as input
   2151 files to the linker, as though they were files to be linked.  *Note
   2152 Implicit Linker Scripts::.
   2153 
   2154 * Menu:
   2155 
   2156 * Basic Script Concepts::	Basic Linker Script Concepts
   2157 * Script Format::		Linker Script Format
   2158 * Simple Example::		Simple Linker Script Example
   2159 * Simple Commands::		Simple Linker Script Commands
   2160 * Assignments::			Assigning Values to Symbols
   2161 * SECTIONS::			SECTIONS Command
   2162 * MEMORY::			MEMORY Command
   2163 * PHDRS::			PHDRS Command
   2164 * VERSION::			VERSION Command
   2165 * Expressions::			Expressions in Linker Scripts
   2166 * Implicit Linker Scripts::	Implicit Linker Scripts
   2167 
   2168 
   2169 File: ld.info,  Node: Basic Script Concepts,  Next: Script Format,  Up: Scripts
   2170 
   2171 3.1 Basic Linker Script Concepts
   2172 ================================
   2173 
   2174 We need to define some basic concepts and vocabulary in order to
   2175 describe the linker script language.
   2176 
   2177    The linker combines input files into a single output file.  The
   2178 output file and each input file are in a special data format known as an
   2179 "object file format".  Each file is called an "object file".  The
   2180 output file is often called an "executable", but for our purposes we
   2181 will also call it an object file.  Each object file has, among other
   2182 things, a list of "sections".  We sometimes refer to a section in an
   2183 input file as an "input section"; similarly, a section in the output
   2184 file is an "output section".
   2185 
   2186    Each section in an object file has a name and a size.  Most sections
   2187 also have an associated block of data, known as the "section contents".
   2188 A section may be marked as "loadable", which mean that the contents
   2189 should be loaded into memory when the output file is run.  A section
   2190 with no contents may be "allocatable", which means that an area in
   2191 memory should be set aside, but nothing in particular should be loaded
   2192 there (in some cases this memory must be zeroed out).  A section which
   2193 is neither loadable nor allocatable typically contains some sort of
   2194 debugging information.
   2195 
   2196    Every loadable or allocatable output section has two addresses.  The
   2197 first is the "VMA", or virtual memory address.  This is the address the
   2198 section will have when the output file is run.  The second is the
   2199 "LMA", or load memory address.  This is the address at which the
   2200 section will be loaded.  In most cases the two addresses will be the
   2201 same.  An example of when they might be different is when a data section
   2202 is loaded into ROM, and then copied into RAM when the program starts up
   2203 (this technique is often used to initialize global variables in a ROM
   2204 based system).  In this case the ROM address would be the LMA, and the
   2205 RAM address would be the VMA.
   2206 
   2207    You can see the sections in an object file by using the `objdump'
   2208 program with the `-h' option.
   2209 
   2210    Every object file also has a list of "symbols", known as the "symbol
   2211 table".  A symbol may be defined or undefined.  Each symbol has a name,
   2212 and each defined symbol has an address, among other information.  If
   2213 you compile a C or C++ program into an object file, you will get a
   2214 defined symbol for every defined function and global or static
   2215 variable.  Every undefined function or global variable which is
   2216 referenced in the input file will become an undefined symbol.
   2217 
   2218    You can see the symbols in an object file by using the `nm' program,
   2219 or by using the `objdump' program with the `-t' option.
   2220 
   2221 
   2222 File: ld.info,  Node: Script Format,  Next: Simple Example,  Prev: Basic Script Concepts,  Up: Scripts
   2223 
   2224 3.2 Linker Script Format
   2225 ========================
   2226 
   2227 Linker scripts are text files.
   2228 
   2229    You write a linker script as a series of commands.  Each command is
   2230 either a keyword, possibly followed by arguments, or an assignment to a
   2231 symbol.  You may separate commands using semicolons.  Whitespace is
   2232 generally ignored.
   2233 
   2234    Strings such as file or format names can normally be entered
   2235 directly.  If the file name contains a character such as a comma which
   2236 would otherwise serve to separate file names, you may put the file name
   2237 in double quotes.  There is no way to use a double quote character in a
   2238 file name.
   2239 
   2240    You may include comments in linker scripts just as in C, delimited by
   2241 `/*' and `*/'.  As in C, comments are syntactically equivalent to
   2242 whitespace.
   2243 
   2244 
   2245 File: ld.info,  Node: Simple Example,  Next: Simple Commands,  Prev: Script Format,  Up: Scripts
   2246 
   2247 3.3 Simple Linker Script Example
   2248 ================================
   2249 
   2250 Many linker scripts are fairly simple.
   2251 
   2252    The simplest possible linker script has just one command:
   2253 `SECTIONS'.  You use the `SECTIONS' command to describe the memory
   2254 layout of the output file.
   2255 
   2256    The `SECTIONS' command is a powerful command.  Here we will describe
   2257 a simple use of it.  Let's assume your program consists only of code,
   2258 initialized data, and uninitialized data.  These will be in the
   2259 `.text', `.data', and `.bss' sections, respectively.  Let's assume
   2260 further that these are the only sections which appear in your input
   2261 files.
   2262 
   2263    For this example, let's say that the code should be loaded at address
   2264 0x10000, and that the data should start at address 0x8000000.  Here is a
   2265 linker script which will do that:
   2266      SECTIONS
   2267      {
   2268        . = 0x10000;
   2269        .text : { *(.text) }
   2270        . = 0x8000000;
   2271        .data : { *(.data) }
   2272        .bss : { *(.bss) }
   2273      }
   2274 
   2275    You write the `SECTIONS' command as the keyword `SECTIONS', followed
   2276 by a series of symbol assignments and output section descriptions
   2277 enclosed in curly braces.
   2278 
   2279    The first line inside the `SECTIONS' command of the above example
   2280 sets the value of the special symbol `.', which is the location
   2281 counter.  If you do not specify the address of an output section in some
   2282 other way (other ways are described later), the address is set from the
   2283 current value of the location counter.  The location counter is then
   2284 incremented by the size of the output section.  At the start of the
   2285 `SECTIONS' command, the location counter has the value `0'.
   2286 
   2287    The second line defines an output section, `.text'.  The colon is
   2288 required syntax which may be ignored for now.  Within the curly braces
   2289 after the output section name, you list the names of the input sections
   2290 which should be placed into this output section.  The `*' is a wildcard
   2291 which matches any file name.  The expression `*(.text)' means all
   2292 `.text' input sections in all input files.
   2293 
   2294    Since the location counter is `0x10000' when the output section
   2295 `.text' is defined, the linker will set the address of the `.text'
   2296 section in the output file to be `0x10000'.
   2297 
   2298    The remaining lines define the `.data' and `.bss' sections in the
   2299 output file.  The linker will place the `.data' output section at
   2300 address `0x8000000'.  After the linker places the `.data' output
   2301 section, the value of the location counter will be `0x8000000' plus the
   2302 size of the `.data' output section.  The effect is that the linker will
   2303 place the `.bss' output section immediately after the `.data' output
   2304 section in memory.
   2305 
   2306    The linker will ensure that each output section has the required
   2307 alignment, by increasing the location counter if necessary.  In this
   2308 example, the specified addresses for the `.text' and `.data' sections
   2309 will probably satisfy any alignment constraints, but the linker may
   2310 have to create a small gap between the `.data' and `.bss' sections.
   2311 
   2312    That's it!  That's a simple and complete linker script.
   2313 
   2314 
   2315 File: ld.info,  Node: Simple Commands,  Next: Assignments,  Prev: Simple Example,  Up: Scripts
   2316 
   2317 3.4 Simple Linker Script Commands
   2318 =================================
   2319 
   2320 In this section we describe the simple linker script commands.
   2321 
   2322 * Menu:
   2323 
   2324 * Entry Point::			Setting the entry point
   2325 * File Commands::		Commands dealing with files
   2326 
   2327 * Format Commands::		Commands dealing with object file formats
   2328 
   2329 * REGION_ALIAS::		Assign alias names to memory regions
   2330 * Miscellaneous Commands::	Other linker script commands
   2331 
   2332 
   2333 File: ld.info,  Node: Entry Point,  Next: File Commands,  Up: Simple Commands
   2334 
   2335 3.4.1 Setting the Entry Point
   2336 -----------------------------
   2337 
   2338 The first instruction to execute in a program is called the "entry
   2339 point".  You can use the `ENTRY' linker script command to set the entry
   2340 point.  The argument is a symbol name:
   2341      ENTRY(SYMBOL)
   2342 
   2343    There are several ways to set the entry point.  The linker will set
   2344 the entry point by trying each of the following methods in order, and
   2345 stopping when one of them succeeds:
   2346    * the `-e' ENTRY command-line option;
   2347 
   2348    * the `ENTRY(SYMBOL)' command in a linker script;
   2349 
   2350    * the value of a target specific symbol, if it is defined;  For many
   2351      targets this is `start', but PE and BeOS based systems for example
   2352      check a list of possible entry symbols, matching the first one
   2353      found.
   2354 
   2355    * the address of the first byte of the `.text' section, if present;
   2356 
   2357    * The address `0'.
   2358 
   2359 
   2360 File: ld.info,  Node: File Commands,  Next: Format Commands,  Prev: Entry Point,  Up: Simple Commands
   2361 
   2362 3.4.2 Commands Dealing with Files
   2363 ---------------------------------
   2364 
   2365 Several linker script commands deal with files.
   2366 
   2367 `INCLUDE FILENAME'
   2368      Include the linker script FILENAME at this point.  The file will
   2369      be searched for in the current directory, and in any directory
   2370      specified with the `-L' option.  You can nest calls to `INCLUDE'
   2371      up to 10 levels deep.
   2372 
   2373      You can place `INCLUDE' directives at the top level, in `MEMORY' or
   2374      `SECTIONS' commands, or in output section descriptions.
   2375 
   2376 `INPUT(FILE, FILE, ...)'
   2377 `INPUT(FILE FILE ...)'
   2378      The `INPUT' command directs the linker to include the named files
   2379      in the link, as though they were named on the command line.
   2380 
   2381      For example, if you always want to include `subr.o' any time you do
   2382      a link, but you can't be bothered to put it on every link command
   2383      line, then you can put `INPUT (subr.o)' in your linker script.
   2384 
   2385      In fact, if you like, you can list all of your input files in the
   2386      linker script, and then invoke the linker with nothing but a `-T'
   2387      option.
   2388 
   2389      In case a "sysroot prefix" is configured, and the filename starts
   2390      with the `/' character, and the script being processed was located
   2391      inside the "sysroot prefix", the filename will be looked for in
   2392      the "sysroot prefix".  Otherwise, the linker will try to open the
   2393      file in the current directory.  If it is not found, the linker
   2394      will search through the archive library search path.  See the
   2395      description of `-L' in *note Command Line Options: Options.
   2396 
   2397      If you use `INPUT (-lFILE)', `ld' will transform the name to
   2398      `libFILE.a', as with the command line argument `-l'.
   2399 
   2400      When you use the `INPUT' command in an implicit linker script, the
   2401      files will be included in the link at the point at which the linker
   2402      script file is included.  This can affect archive searching.
   2403 
   2404 `GROUP(FILE, FILE, ...)'
   2405 `GROUP(FILE FILE ...)'
   2406      The `GROUP' command is like `INPUT', except that the named files
   2407      should all be archives, and they are searched repeatedly until no
   2408      new undefined references are created.  See the description of `-('
   2409      in *note Command Line Options: Options.
   2410 
   2411 `AS_NEEDED(FILE, FILE, ...)'
   2412 `AS_NEEDED(FILE FILE ...)'
   2413      This construct can appear only inside of the `INPUT' or `GROUP'
   2414      commands, among other filenames.  The files listed will be handled
   2415      as if they appear directly in the `INPUT' or `GROUP' commands,
   2416      with the exception of ELF shared libraries, that will be added only
   2417      when they are actually needed.  This construct essentially enables
   2418      `--as-needed' option for all the files listed inside of it and
   2419      restores previous `--as-needed' resp. `--no-as-needed' setting
   2420      afterwards.
   2421 
   2422 `OUTPUT(FILENAME)'
   2423      The `OUTPUT' command names the output file.  Using
   2424      `OUTPUT(FILENAME)' in the linker script is exactly like using `-o
   2425      FILENAME' on the command line (*note Command Line Options:
   2426      Options.).  If both are used, the command line option takes
   2427      precedence.
   2428 
   2429      You can use the `OUTPUT' command to define a default name for the
   2430      output file other than the usual default of `a.out'.
   2431 
   2432 `SEARCH_DIR(PATH)'
   2433      The `SEARCH_DIR' command adds PATH to the list of paths where `ld'
   2434      looks for archive libraries.  Using `SEARCH_DIR(PATH)' is exactly
   2435      like using `-L PATH' on the command line (*note Command Line
   2436      Options: Options.).  If both are used, then the linker will search
   2437      both paths.  Paths specified using the command line option are
   2438      searched first.
   2439 
   2440 `STARTUP(FILENAME)'
   2441      The `STARTUP' command is just like the `INPUT' command, except
   2442      that FILENAME will become the first input file to be linked, as
   2443      though it were specified first on the command line.  This may be
   2444      useful when using a system in which the entry point is always the
   2445      start of the first file.
   2446 
   2447 
   2448 File: ld.info,  Node: Format Commands,  Next: REGION_ALIAS,  Prev: File Commands,  Up: Simple Commands
   2449 
   2450 3.4.3 Commands Dealing with Object File Formats
   2451 -----------------------------------------------
   2452 
   2453 A couple of linker script commands deal with object file formats.
   2454 
   2455 `OUTPUT_FORMAT(BFDNAME)'
   2456 `OUTPUT_FORMAT(DEFAULT, BIG, LITTLE)'
   2457      The `OUTPUT_FORMAT' command names the BFD format to use for the
   2458      output file (*note BFD::).  Using `OUTPUT_FORMAT(BFDNAME)' is
   2459      exactly like using `--oformat BFDNAME' on the command line (*note
   2460      Command Line Options: Options.).  If both are used, the command
   2461      line option takes precedence.
   2462 
   2463      You can use `OUTPUT_FORMAT' with three arguments to use different
   2464      formats based on the `-EB' and `-EL' command line options.  This
   2465      permits the linker script to set the output format based on the
   2466      desired endianness.
   2467 
   2468      If neither `-EB' nor `-EL' are used, then the output format will
   2469      be the first argument, DEFAULT.  If `-EB' is used, the output
   2470      format will be the second argument, BIG.  If `-EL' is used, the
   2471      output format will be the third argument, LITTLE.
   2472 
   2473      For example, the default linker script for the MIPS ELF target
   2474      uses this command:
   2475           OUTPUT_FORMAT(elf32-bigmips, elf32-bigmips, elf32-littlemips)
   2476      This says that the default format for the output file is
   2477      `elf32-bigmips', but if the user uses the `-EL' command line
   2478      option, the output file will be created in the `elf32-littlemips'
   2479      format.
   2480 
   2481 `TARGET(BFDNAME)'
   2482      The `TARGET' command names the BFD format to use when reading input
   2483      files.  It affects subsequent `INPUT' and `GROUP' commands.  This
   2484      command is like using `-b BFDNAME' on the command line (*note
   2485      Command Line Options: Options.).  If the `TARGET' command is used
   2486      but `OUTPUT_FORMAT' is not, then the last `TARGET' command is also
   2487      used to set the format for the output file.  *Note BFD::.
   2488 
   2489 
   2490 File: ld.info,  Node: REGION_ALIAS,  Next: Miscellaneous Commands,  Prev: Format Commands,  Up: Simple Commands
   2491 
   2492 3.4.4 Assign alias names to memory regions
   2493 ------------------------------------------
   2494 
   2495 Alias names can be added to existing memory regions created with the
   2496 *note MEMORY:: command.  Each name corresponds to at most one memory
   2497 region.
   2498 
   2499      REGION_ALIAS(ALIAS, REGION)
   2500 
   2501    The `REGION_ALIAS' function creates an alias name ALIAS for the
   2502 memory region REGION.  This allows a flexible mapping of output sections
   2503 to memory regions.  An example follows.
   2504 
   2505    Suppose we have an application for embedded systems which come with
   2506 various memory storage devices.  All have a general purpose, volatile
   2507 memory `RAM' that allows code execution or data storage.  Some may have
   2508 a read-only, non-volatile memory `ROM' that allows code execution and
   2509 read-only data access.  The last variant is a read-only, non-volatile
   2510 memory `ROM2' with read-only data access and no code execution
   2511 capability.  We have four output sections:
   2512 
   2513    * `.text' program code;
   2514 
   2515    * `.rodata' read-only data;
   2516 
   2517    * `.data' read-write initialized data;
   2518 
   2519    * `.bss' read-write zero initialized data.
   2520 
   2521    The goal is to provide a linker command file that contains a system
   2522 independent part defining the output sections and a system dependent
   2523 part mapping the output sections to the memory regions available on the
   2524 system.  Our embedded systems come with three different memory setups
   2525 `A', `B' and `C':
   2526 Section            Variant A          Variant B          Variant C
   2527 .text              RAM                ROM                ROM
   2528 .rodata            RAM                ROM                ROM2
   2529 .data              RAM                RAM/ROM            RAM/ROM2
   2530 .bss               RAM                RAM                RAM
   2531    The notation `RAM/ROM' or `RAM/ROM2' means that this section is
   2532 loaded into region `ROM' or `ROM2' respectively.  Please note that the
   2533 load address of the `.data' section starts in all three variants at the
   2534 end of the `.rodata' section.
   2535 
   2536    The base linker script that deals with the output sections follows.
   2537 It includes the system dependent `linkcmds.memory' file that describes
   2538 the memory layout:
   2539      INCLUDE linkcmds.memory
   2540 
   2541      SECTIONS
   2542        {
   2543          .text :
   2544            {
   2545              *(.text)
   2546            } > REGION_TEXT
   2547          .rodata :
   2548            {
   2549              *(.rodata)
   2550              rodata_end = .;
   2551            } > REGION_RODATA
   2552          .data : AT (rodata_end)
   2553            {
   2554              data_start = .;
   2555              *(.data)
   2556            } > REGION_DATA
   2557          data_size = SIZEOF(.data);
   2558          data_load_start = LOADADDR(.data);
   2559          .bss :
   2560            {
   2561              *(.bss)
   2562            } > REGION_BSS
   2563        }
   2564 
   2565    Now we need three different `linkcmds.memory' files to define memory
   2566 regions and alias names.  The content of `linkcmds.memory' for the three
   2567 variants `A', `B' and `C':
   2568 `A'
   2569      Here everything goes into the `RAM'.
   2570           MEMORY
   2571             {
   2572               RAM : ORIGIN = 0, LENGTH = 4M
   2573             }
   2574 
   2575           REGION_ALIAS("REGION_TEXT", RAM);
   2576           REGION_ALIAS("REGION_RODATA", RAM);
   2577           REGION_ALIAS("REGION_DATA", RAM);
   2578           REGION_ALIAS("REGION_BSS", RAM);
   2579 
   2580 `B'
   2581      Program code and read-only data go into the `ROM'.  Read-write
   2582      data goes into the `RAM'.  An image of the initialized data is
   2583      loaded into the `ROM' and will be copied during system start into
   2584      the `RAM'.
   2585           MEMORY
   2586             {
   2587               ROM : ORIGIN = 0, LENGTH = 3M
   2588               RAM : ORIGIN = 0x10000000, LENGTH = 1M
   2589             }
   2590 
   2591           REGION_ALIAS("REGION_TEXT", ROM);
   2592           REGION_ALIAS("REGION_RODATA", ROM);
   2593           REGION_ALIAS("REGION_DATA", RAM);
   2594           REGION_ALIAS("REGION_BSS", RAM);
   2595 
   2596 `C'
   2597      Program code goes into the `ROM'.  Read-only data goes into the
   2598      `ROM2'.  Read-write data goes into the `RAM'.  An image of the
   2599      initialized data is loaded into the `ROM2' and will be copied
   2600      during system start into the `RAM'.
   2601           MEMORY
   2602             {
   2603               ROM : ORIGIN = 0, LENGTH = 2M
   2604               ROM2 : ORIGIN = 0x10000000, LENGTH = 1M
   2605               RAM : ORIGIN = 0x20000000, LENGTH = 1M
   2606             }
   2607 
   2608           REGION_ALIAS("REGION_TEXT", ROM);
   2609           REGION_ALIAS("REGION_RODATA", ROM2);
   2610           REGION_ALIAS("REGION_DATA", RAM);
   2611           REGION_ALIAS("REGION_BSS", RAM);
   2612 
   2613    It is possible to write a common system initialization routine to
   2614 copy the `.data' section from `ROM' or `ROM2' into the `RAM' if
   2615 necessary:
   2616      #include <string.h>
   2617 
   2618      extern char data_start [];
   2619      extern char data_size [];
   2620      extern char data_load_start [];
   2621 
   2622      void copy_data(void)
   2623      {
   2624        if (data_start != data_load_start)
   2625          {
   2626            memcpy(data_start, data_load_start, (size_t) data_size);
   2627          }
   2628      }
   2629 
   2630 
   2631 File: ld.info,  Node: Miscellaneous Commands,  Prev: REGION_ALIAS,  Up: Simple Commands
   2632 
   2633 3.4.5 Other Linker Script Commands
   2634 ----------------------------------
   2635 
   2636 There are a few other linker scripts commands.
   2637 
   2638 `ASSERT(EXP, MESSAGE)'
   2639      Ensure that EXP is non-zero.  If it is zero, then exit the linker
   2640      with an error code, and print MESSAGE.
   2641 
   2642 `EXTERN(SYMBOL SYMBOL ...)'
   2643      Force SYMBOL to be entered in the output file as an undefined
   2644      symbol.  Doing this may, for example, trigger linking of additional
   2645      modules from standard libraries.  You may list several SYMBOLs for
   2646      each `EXTERN', and you may use `EXTERN' multiple times.  This
   2647      command has the same effect as the `-u' command-line option.
   2648 
   2649 `FORCE_COMMON_ALLOCATION'
   2650      This command has the same effect as the `-d' command-line option:
   2651      to make `ld' assign space to common symbols even if a relocatable
   2652      output file is specified (`-r').
   2653 
   2654 `INHIBIT_COMMON_ALLOCATION'
   2655      This command has the same effect as the `--no-define-common'
   2656      command-line option: to make `ld' omit the assignment of addresses
   2657      to common symbols even for a non-relocatable output file.
   2658 
   2659 `INSERT [ AFTER | BEFORE ] OUTPUT_SECTION'
   2660      This command is typically used in a script specified by `-T' to
   2661      augment the default `SECTIONS' with, for example, overlays.  It
   2662      inserts all prior linker script statements after (or before)
   2663      OUTPUT_SECTION, and also causes `-T' to not override the default
   2664      linker script.  The exact insertion point is as for orphan
   2665      sections.  *Note Location Counter::.  The insertion happens after
   2666      the linker has mapped input sections to output sections.  Prior to
   2667      the insertion, since `-T' scripts are parsed before the default
   2668      linker script, statements in the `-T' script occur before the
   2669      default linker script statements in the internal linker
   2670      representation of the script.  In particular, input section
   2671      assignments will be made to `-T' output sections before those in
   2672      the default script.  Here is an example of how a `-T' script using
   2673      `INSERT' might look:
   2674 
   2675           SECTIONS
   2676           {
   2677             OVERLAY :
   2678             {
   2679               .ov1 { ov1*(.text) }
   2680               .ov2 { ov2*(.text) }
   2681             }
   2682           }
   2683           INSERT AFTER .text;
   2684 
   2685 `NOCROSSREFS(SECTION SECTION ...)'
   2686      This command may be used to tell `ld' to issue an error about any
   2687      references among certain output sections.
   2688 
   2689      In certain types of programs, particularly on embedded systems when
   2690      using overlays, when one section is loaded into memory, another
   2691      section will not be.  Any direct references between the two
   2692      sections would be errors.  For example, it would be an error if
   2693      code in one section called a function defined in the other section.
   2694 
   2695      The `NOCROSSREFS' command takes a list of output section names.  If
   2696      `ld' detects any cross references between the sections, it reports
   2697      an error and returns a non-zero exit status.  Note that the
   2698      `NOCROSSREFS' command uses output section names, not input section
   2699      names.
   2700 
   2701 `OUTPUT_ARCH(BFDARCH)'
   2702      Specify a particular output machine architecture.  The argument is
   2703      one of the names used by the BFD library (*note BFD::).  You can
   2704      see the architecture of an object file by using the `objdump'
   2705      program with the `-f' option.
   2706 
   2707 
   2708 File: ld.info,  Node: Assignments,  Next: SECTIONS,  Prev: Simple Commands,  Up: Scripts
   2709 
   2710 3.5 Assigning Values to Symbols
   2711 ===============================
   2712 
   2713 You may assign a value to a symbol in a linker script.  This will define
   2714 the symbol and place it into the symbol table with a global scope.
   2715 
   2716 * Menu:
   2717 
   2718 * Simple Assignments::		Simple Assignments
   2719 * PROVIDE::			PROVIDE
   2720 * PROVIDE_HIDDEN::		PROVIDE_HIDDEN
   2721 * Source Code Reference::	How to use a linker script defined symbol in source code
   2722 
   2723 
   2724 File: ld.info,  Node: Simple Assignments,  Next: PROVIDE,  Up: Assignments
   2725 
   2726 3.5.1 Simple Assignments
   2727 ------------------------
   2728 
   2729 You may assign to a symbol using any of the C assignment operators:
   2730 
   2731 `SYMBOL = EXPRESSION ;'
   2732 `SYMBOL += EXPRESSION ;'
   2733 `SYMBOL -= EXPRESSION ;'
   2734 `SYMBOL *= EXPRESSION ;'
   2735 `SYMBOL /= EXPRESSION ;'
   2736 `SYMBOL <<= EXPRESSION ;'
   2737 `SYMBOL >>= EXPRESSION ;'
   2738 `SYMBOL &= EXPRESSION ;'
   2739 `SYMBOL |= EXPRESSION ;'
   2740 
   2741    The first case will define SYMBOL to the value of EXPRESSION.  In
   2742 the other cases, SYMBOL must already be defined, and the value will be
   2743 adjusted accordingly.
   2744 
   2745    The special symbol name `.' indicates the location counter.  You may
   2746 only use this within a `SECTIONS' command.  *Note Location Counter::.
   2747 
   2748    The semicolon after EXPRESSION is required.
   2749 
   2750    Expressions are defined below; see *note Expressions::.
   2751 
   2752    You may write symbol assignments as commands in their own right, or
   2753 as statements within a `SECTIONS' command, or as part of an output
   2754 section description in a `SECTIONS' command.
   2755 
   2756    The section of the symbol will be set from the section of the
   2757 expression; for more information, see *note Expression Section::.
   2758 
   2759    Here is an example showing the three different places that symbol
   2760 assignments may be used:
   2761 
   2762      floating_point = 0;
   2763      SECTIONS
   2764      {
   2765        .text :
   2766          {
   2767            *(.text)
   2768            _etext = .;
   2769          }
   2770        _bdata = (. + 3) & ~ 3;
   2771        .data : { *(.data) }
   2772      }
   2773    In this example, the symbol `floating_point' will be defined as
   2774 zero.  The symbol `_etext' will be defined as the address following the
   2775 last `.text' input section.  The symbol `_bdata' will be defined as the
   2776 address following the `.text' output section aligned upward to a 4 byte
   2777 boundary.
   2778 
   2779 
   2780 File: ld.info,  Node: PROVIDE,  Next: PROVIDE_HIDDEN,  Prev: Simple Assignments,  Up: Assignments
   2781 
   2782 3.5.2 PROVIDE
   2783 -------------
   2784 
   2785 In some cases, it is desirable for a linker script to define a symbol
   2786 only if it is referenced and is not defined by any object included in
   2787 the link.  For example, traditional linkers defined the symbol `etext'.
   2788 However, ANSI C requires that the user be able to use `etext' as a
   2789 function name without encountering an error.  The `PROVIDE' keyword may
   2790 be used to define a symbol, such as `etext', only if it is referenced
   2791 but not defined.  The syntax is `PROVIDE(SYMBOL = EXPRESSION)'.
   2792 
   2793    Here is an example of using `PROVIDE' to define `etext':
   2794      SECTIONS
   2795      {
   2796        .text :
   2797          {
   2798            *(.text)
   2799            _etext = .;
   2800            PROVIDE(etext = .);
   2801          }
   2802      }
   2803 
   2804    In this example, if the program defines `_etext' (with a leading
   2805 underscore), the linker will give a multiple definition error.  If, on
   2806 the other hand, the program defines `etext' (with no leading
   2807 underscore), the linker will silently use the definition in the program.
   2808 If the program references `etext' but does not define it, the linker
   2809 will use the definition in the linker script.
   2810 
   2811 
   2812 File: ld.info,  Node: PROVIDE_HIDDEN,  Next: Source Code Reference,  Prev: PROVIDE,  Up: Assignments
   2813 
   2814 3.5.3 PROVIDE_HIDDEN
   2815 --------------------
   2816 
   2817 Similar to `PROVIDE'.  For ELF targeted ports, the symbol will be
   2818 hidden and won't be exported.
   2819 
   2820 
   2821 File: ld.info,  Node: Source Code Reference,  Prev: PROVIDE_HIDDEN,  Up: Assignments
   2822 
   2823 3.5.4 Source Code Reference
   2824 ---------------------------
   2825 
   2826 Accessing a linker script defined variable from source code is not
   2827 intuitive.  In particular a linker script symbol is not equivalent to a
   2828 variable declaration in a high level language, it is instead a symbol
   2829 that does not have a value.
   2830 
   2831    Before going further, it is important to note that compilers often
   2832 transform names in the source code into different names when they are
   2833 stored in the symbol table.  For example, Fortran compilers commonly
   2834 prepend or append an underscore, and C++ performs extensive `name
   2835 mangling'.  Therefore there might be a discrepancy between the name of
   2836 a variable as it is used in source code and the name of the same
   2837 variable as it is defined in a linker script.  For example in C a
   2838 linker script variable might be referred to as:
   2839 
   2840        extern int foo;
   2841 
   2842    But in the linker script it might be defined as:
   2843 
   2844        _foo = 1000;
   2845 
   2846    In the remaining examples however it is assumed that no name
   2847 transformation has taken place.
   2848 
   2849    When a symbol is declared in a high level language such as C, two
   2850 things happen.  The first is that the compiler reserves enough space in
   2851 the program's memory to hold the _value_ of the symbol.  The second is
   2852 that the compiler creates an entry in the program's symbol table which
   2853 holds the symbol's _address_.  ie the symbol table contains the address
   2854 of the block of memory holding the symbol's value.  So for example the
   2855 following C declaration, at file scope:
   2856 
   2857        int foo = 1000;
   2858 
   2859    creates a entry called `foo' in the symbol table.  This entry holds
   2860 the address of an `int' sized block of memory where the number 1000 is
   2861 initially stored.
   2862 
   2863    When a program references a symbol the compiler generates code that
   2864 first accesses the symbol table to find the address of the symbol's
   2865 memory block and then code to read the value from that memory block.
   2866 So:
   2867 
   2868        foo = 1;
   2869 
   2870    looks up the symbol `foo' in the symbol table, gets the address
   2871 associated with this symbol and then writes the value 1 into that
   2872 address.  Whereas:
   2873 
   2874        int * a = & foo;
   2875 
   2876    looks up the symbol `foo' in the symbol table, gets it address and
   2877 then copies this address into the block of memory associated with the
   2878 variable `a'.
   2879 
   2880    Linker scripts symbol declarations, by contrast, create an entry in
   2881 the symbol table but do not assign any memory to them.  Thus they are
   2882 an address without a value.  So for example the linker script
   2883 definition:
   2884 
   2885        foo = 1000;
   2886 
   2887    creates an entry in the symbol table called `foo' which holds the
   2888 address of memory location 1000, but nothing special is stored at
   2889 address 1000.  This means that you cannot access the _value_ of a
   2890 linker script defined symbol - it has no value - all you can do is
   2891 access the _address_ of a linker script defined symbol.
   2892 
   2893    Hence when you are using a linker script defined symbol in source
   2894 code you should always take the address of the symbol, and never
   2895 attempt to use its value.  For example suppose you want to copy the
   2896 contents of a section of memory called .ROM into a section called
   2897 .FLASH and the linker script contains these declarations:
   2898 
   2899        start_of_ROM   = .ROM;
   2900        end_of_ROM     = .ROM + sizeof (.ROM) - 1;
   2901        start_of_FLASH = .FLASH;
   2902 
   2903    Then the C source code to perform the copy would be:
   2904 
   2905        extern char start_of_ROM, end_of_ROM, start_of_FLASH;
   2906 
   2907        memcpy (& start_of_FLASH, & start_of_ROM, & end_of_ROM - & start_of_ROM);
   2908 
   2909    Note the use of the `&' operators.  These are correct.
   2910 
   2911 
   2912 File: ld.info,  Node: SECTIONS,  Next: MEMORY,  Prev: Assignments,  Up: Scripts
   2913 
   2914 3.6 SECTIONS Command
   2915 ====================
   2916 
   2917 The `SECTIONS' command tells the linker how to map input sections into
   2918 output sections, and how to place the output sections in memory.
   2919 
   2920    The format of the `SECTIONS' command is:
   2921      SECTIONS
   2922      {
   2923        SECTIONS-COMMAND
   2924        SECTIONS-COMMAND
   2925        ...
   2926      }
   2927 
   2928    Each SECTIONS-COMMAND may of be one of the following:
   2929 
   2930    * an `ENTRY' command (*note Entry command: Entry Point.)
   2931 
   2932    * a symbol assignment (*note Assignments::)
   2933 
   2934    * an output section description
   2935 
   2936    * an overlay description
   2937 
   2938    The `ENTRY' command and symbol assignments are permitted inside the
   2939 `SECTIONS' command for convenience in using the location counter in
   2940 those commands.  This can also make the linker script easier to
   2941 understand because you can use those commands at meaningful points in
   2942 the layout of the output file.
   2943 
   2944    Output section descriptions and overlay descriptions are described
   2945 below.
   2946 
   2947    If you do not use a `SECTIONS' command in your linker script, the
   2948 linker will place each input section into an identically named output
   2949 section in the order that the sections are first encountered in the
   2950 input files.  If all input sections are present in the first file, for
   2951 example, the order of sections in the output file will match the order
   2952 in the first input file.  The first section will be at address zero.
   2953 
   2954 * Menu:
   2955 
   2956 * Output Section Description::	Output section description
   2957 * Output Section Name::		Output section name
   2958 * Output Section Address::	Output section address
   2959 * Input Section::		Input section description
   2960 * Output Section Data::		Output section data
   2961 * Output Section Keywords::	Output section keywords
   2962 * Output Section Discarding::	Output section discarding
   2963 * Output Section Attributes::	Output section attributes
   2964 * Overlay Description::		Overlay description
   2965 
   2966 
   2967 File: ld.info,  Node: Output Section Description,  Next: Output Section Name,  Up: SECTIONS
   2968 
   2969 3.6.1 Output Section Description
   2970 --------------------------------
   2971 
   2972 The full description of an output section looks like this:
   2973      SECTION [ADDRESS] [(TYPE)] :
   2974        [AT(LMA)]
   2975        [ALIGN(SECTION_ALIGN)]
   2976        [SUBALIGN(SUBSECTION_ALIGN)]
   2977        [CONSTRAINT]
   2978        {
   2979          OUTPUT-SECTION-COMMAND
   2980          OUTPUT-SECTION-COMMAND
   2981          ...
   2982        } [>REGION] [AT>LMA_REGION] [:PHDR :PHDR ...] [=FILLEXP]
   2983 
   2984    Most output sections do not use most of the optional section
   2985 attributes.
   2986 
   2987    The whitespace around SECTION is required, so that the section name
   2988 is unambiguous.  The colon and the curly braces are also required.  The
   2989 line breaks and other white space are optional.
   2990 
   2991    Each OUTPUT-SECTION-COMMAND may be one of the following:
   2992 
   2993    * a symbol assignment (*note Assignments::)
   2994 
   2995    * an input section description (*note Input Section::)
   2996 
   2997    * data values to include directly (*note Output Section Data::)
   2998 
   2999    * a special output section keyword (*note Output Section Keywords::)
   3000 
   3001 
   3002 File: ld.info,  Node: Output Section Name,  Next: Output Section Address,  Prev: Output Section Description,  Up: SECTIONS
   3003 
   3004 3.6.2 Output Section Name
   3005 -------------------------
   3006 
   3007 The name of the output section is SECTION.  SECTION must meet the
   3008 constraints of your output format.  In formats which only support a
   3009 limited number of sections, such as `a.out', the name must be one of
   3010 the names supported by the format (`a.out', for example, allows only
   3011 `.text', `.data' or `.bss'). If the output format supports any number
   3012 of sections, but with numbers and not names (as is the case for Oasys),
   3013 the name should be supplied as a quoted numeric string.  A section name
   3014 may consist of any sequence of characters, but a name which contains
   3015 any unusual characters such as commas must be quoted.
   3016 
   3017    The output section name `/DISCARD/' is special; *note Output Section
   3018 Discarding::.
   3019 
   3020 
   3021 File: ld.info,  Node: Output Section Address,  Next: Input Section,  Prev: Output Section Name,  Up: SECTIONS
   3022 
   3023 3.6.3 Output Section Address
   3024 ----------------------------
   3025 
   3026 The ADDRESS is an expression for the VMA (the virtual memory address)
   3027 of the output section.  This address is optional, but if it is provided
   3028 then the output address will be set exactly as specified.
   3029 
   3030    If the output address is not specified then one will be chosen for
   3031 the section, based on the heuristic below.  This address will be
   3032 adjusted to fit the alignment requirement of the output section.  The
   3033 alignment requirement is the strictest alignment of any input section
   3034 contained within the output section.
   3035 
   3036    The output section address heuristic is as follows:
   3037 
   3038    * If an output memory REGION is set for the section then it is added
   3039      to this region and its address will be the next free address in
   3040      that region.
   3041 
   3042    * If the MEMORY command has been used to create a list of memory
   3043      regions then the first region which has attributes compatible with
   3044      the section is selected to contain it.  The section's output
   3045      address will be the next free address in that region; *note
   3046      MEMORY::.
   3047 
   3048    * If no memory regions were specified, or none match the section then
   3049      the output address will be based on the current value of the
   3050      location counter.
   3051 
   3052 For example:
   3053 
   3054      .text . : { *(.text) }
   3055 
   3056 and
   3057 
   3058      .text : { *(.text) }
   3059 
   3060 are subtly different.  The first will set the address of the `.text'
   3061 output section to the current value of the location counter.  The
   3062 second will set it to the current value of the location counter aligned
   3063 to the strictest alignment of any of the `.text' input sections.
   3064 
   3065    The ADDRESS may be an arbitrary expression; *note Expressions::.
   3066 For example, if you want to align the section on a 0x10 byte boundary,
   3067 so that the lowest four bits of the section address are zero, you could
   3068 do something like this:
   3069      .text ALIGN(0x10) : { *(.text) }
   3070    This works because `ALIGN' returns the current location counter
   3071 aligned upward to the specified value.
   3072 
   3073    Specifying ADDRESS for a section will change the value of the
   3074 location counter, provided that the section is non-empty.  (Empty
   3075 sections are ignored).
   3076 
   3077 
   3078 File: ld.info,  Node: Input Section,  Next: Output Section Data,  Prev: Output Section Address,  Up: SECTIONS
   3079 
   3080 3.6.4 Input Section Description
   3081 -------------------------------
   3082 
   3083 The most common output section command is an input section description.
   3084 
   3085    The input section description is the most basic linker script
   3086 operation.  You use output sections to tell the linker how to lay out
   3087 your program in memory.  You use input section descriptions to tell the
   3088 linker how to map the input files into your memory layout.
   3089 
   3090 * Menu:
   3091 
   3092 * Input Section Basics::	Input section basics
   3093 * Input Section Wildcards::	Input section wildcard patterns
   3094 * Input Section Common::	Input section for common symbols
   3095 * Input Section Keep::		Input section and garbage collection
   3096 * Input Section Example::	Input section example
   3097 
   3098 
   3099 File: ld.info,  Node: Input Section Basics,  Next: Input Section Wildcards,  Up: Input Section
   3100 
   3101 3.6.4.1 Input Section Basics
   3102 ............................
   3103 
   3104 An input section description consists of a file name optionally followed
   3105 by a list of section names in parentheses.
   3106 
   3107    The file name and the section name may be wildcard patterns, which we
   3108 describe further below (*note Input Section Wildcards::).
   3109 
   3110    The most common input section description is to include all input
   3111 sections with a particular name in the output section.  For example, to
   3112 include all input `.text' sections, you would write:
   3113      *(.text)
   3114    Here the `*' is a wildcard which matches any file name.  To exclude
   3115 a list of files from matching the file name wildcard, EXCLUDE_FILE may
   3116 be used to match all files except the ones specified in the
   3117 EXCLUDE_FILE list.  For example:
   3118      *(EXCLUDE_FILE (*crtend.o *otherfile.o) .ctors)
   3119    will cause all .ctors sections from all files except `crtend.o' and
   3120 `otherfile.o' to be included.
   3121 
   3122    There are two ways to include more than one section:
   3123      *(.text .rdata)
   3124      *(.text) *(.rdata)
   3125    The difference between these is the order in which the `.text' and
   3126 `.rdata' input sections will appear in the output section.  In the
   3127 first example, they will be intermingled, appearing in the same order as
   3128 they are found in the linker input.  In the second example, all `.text'
   3129 input sections will appear first, followed by all `.rdata' input
   3130 sections.
   3131 
   3132    You can specify a file name to include sections from a particular
   3133 file.  You would do this if one or more of your files contain special
   3134 data that needs to be at a particular location in memory.  For example:
   3135      data.o(.data)
   3136 
   3137    You can also specify files within archives by writing a pattern
   3138 matching the archive, a colon, then the pattern matching the file, with
   3139 no whitespace around the colon.
   3140 
   3141 `archive:file'
   3142      matches file within archive
   3143 
   3144 `archive:'
   3145      matches the whole archive
   3146 
   3147 `:file'
   3148      matches file but not one in an archive
   3149 
   3150    Either one or both of `archive' and `file' can contain shell
   3151 wildcards.  On DOS based file systems, the linker will assume that a
   3152 single letter followed by a colon is a drive specifier, so `c:myfile.o'
   3153 is a simple file specification, not `myfile.o' within an archive called
   3154 `c'.  `archive:file' filespecs may also be used within an
   3155 `EXCLUDE_FILE' list, but may not appear in other linker script
   3156 contexts.  For instance, you cannot extract a file from an archive by
   3157 using `archive:file' in an `INPUT' command.
   3158 
   3159    If you use a file name without a list of sections, then all sections
   3160 in the input file will be included in the output section.  This is not
   3161 commonly done, but it may by useful on occasion.  For example:
   3162      data.o
   3163 
   3164    When you use a file name which is not an `archive:file' specifier
   3165 and does not contain any wild card characters, the linker will first
   3166 see if you also specified the file name on the linker command line or
   3167 in an `INPUT' command.  If you did not, the linker will attempt to open
   3168 the file as an input file, as though it appeared on the command line.
   3169 Note that this differs from an `INPUT' command, because the linker will
   3170 not search for the file in the archive search path.
   3171 
   3172 
   3173 File: ld.info,  Node: Input Section Wildcards,  Next: Input Section Common,  Prev: Input Section Basics,  Up: Input Section
   3174 
   3175 3.6.4.2 Input Section Wildcard Patterns
   3176 .......................................
   3177 
   3178 In an input section description, either the file name or the section
   3179 name or both may be wildcard patterns.
   3180 
   3181    The file name of `*' seen in many examples is a simple wildcard
   3182 pattern for the file name.
   3183 
   3184    The wildcard patterns are like those used by the Unix shell.
   3185 
   3186 `*'
   3187      matches any number of characters
   3188 
   3189 `?'
   3190      matches any single character
   3191 
   3192 `[CHARS]'
   3193      matches a single instance of any of the CHARS; the `-' character
   3194      may be used to specify a range of characters, as in `[a-z]' to
   3195      match any lower case letter
   3196 
   3197 `\'
   3198      quotes the following character
   3199 
   3200    When a file name is matched with a wildcard, the wildcard characters
   3201 will not match a `/' character (used to separate directory names on
   3202 Unix).  A pattern consisting of a single `*' character is an exception;
   3203 it will always match any file name, whether it contains a `/' or not.
   3204 In a section name, the wildcard characters will match a `/' character.
   3205 
   3206    File name wildcard patterns only match files which are explicitly
   3207 specified on the command line or in an `INPUT' command.  The linker
   3208 does not search directories to expand wildcards.
   3209 
   3210    If a file name matches more than one wildcard pattern, or if a file
   3211 name appears explicitly and is also matched by a wildcard pattern, the
   3212 linker will use the first match in the linker script.  For example, this
   3213 sequence of input section descriptions is probably in error, because the
   3214 `data.o' rule will not be used:
   3215      .data : { *(.data) }
   3216      .data1 : { data.o(.data) }
   3217 
   3218    Normally, the linker will place files and sections matched by
   3219 wildcards in the order in which they are seen during the link.  You can
   3220 change this by using the `SORT_BY_NAME' keyword, which appears before a
   3221 wildcard pattern in parentheses (e.g., `SORT_BY_NAME(.text*)').  When
   3222 the `SORT_BY_NAME' keyword is used, the linker will sort the files or
   3223 sections into ascending order by name before placing them in the output
   3224 file.
   3225 
   3226    `SORT_BY_ALIGNMENT' is very similar to `SORT_BY_NAME'. The
   3227 difference is `SORT_BY_ALIGNMENT' will sort sections into ascending
   3228 order by alignment before placing them in the output file.
   3229 
   3230    `SORT' is an alias for `SORT_BY_NAME'.
   3231 
   3232    When there are nested section sorting commands in linker script,
   3233 there can be at most 1 level of nesting for section sorting commands.
   3234 
   3235   1. `SORT_BY_NAME' (`SORT_BY_ALIGNMENT' (wildcard section pattern)).
   3236      It will sort the input sections by name first, then by alignment
   3237      if 2 sections have the same name.
   3238 
   3239   2. `SORT_BY_ALIGNMENT' (`SORT_BY_NAME' (wildcard section pattern)).
   3240      It will sort the input sections by alignment first, then by name
   3241      if 2 sections have the same alignment.
   3242 
   3243   3. `SORT_BY_NAME' (`SORT_BY_NAME' (wildcard section pattern)) is
   3244      treated the same as `SORT_BY_NAME' (wildcard section pattern).
   3245 
   3246   4. `SORT_BY_ALIGNMENT' (`SORT_BY_ALIGNMENT' (wildcard section
   3247      pattern)) is treated the same as `SORT_BY_ALIGNMENT' (wildcard
   3248      section pattern).
   3249 
   3250   5. All other nested section sorting commands are invalid.
   3251 
   3252    When both command line section sorting option and linker script
   3253 section sorting command are used, section sorting command always takes
   3254 precedence over the command line option.
   3255 
   3256    If the section sorting command in linker script isn't nested, the
   3257 command line option will make the section sorting command to be treated
   3258 as nested sorting command.
   3259 
   3260   1. `SORT_BY_NAME' (wildcard section pattern ) with `--sort-sections
   3261      alignment' is equivalent to `SORT_BY_NAME' (`SORT_BY_ALIGNMENT'
   3262      (wildcard section pattern)).
   3263 
   3264   2. `SORT_BY_ALIGNMENT' (wildcard section pattern) with
   3265      `--sort-section name' is equivalent to `SORT_BY_ALIGNMENT'
   3266      (`SORT_BY_NAME' (wildcard section pattern)).
   3267 
   3268    If the section sorting command in linker script is nested, the
   3269 command line option will be ignored.
   3270 
   3271    If you ever get confused about where input sections are going, use
   3272 the `-M' linker option to generate a map file.  The map file shows
   3273 precisely how input sections are mapped to output sections.
   3274 
   3275    This example shows how wildcard patterns might be used to partition
   3276 files.  This linker script directs the linker to place all `.text'
   3277 sections in `.text' and all `.bss' sections in `.bss'.  The linker will
   3278 place the `.data' section from all files beginning with an upper case
   3279 character in `.DATA'; for all other files, the linker will place the
   3280 `.data' section in `.data'.
   3281      SECTIONS {
   3282        .text : { *(.text) }
   3283        .DATA : { [A-Z]*(.data) }
   3284        .data : { *(.data) }
   3285        .bss : { *(.bss) }
   3286      }
   3287 
   3288 
   3289 File: ld.info,  Node: Input Section Common,  Next: Input Section Keep,  Prev: Input Section Wildcards,  Up: Input Section
   3290 
   3291 3.6.4.3 Input Section for Common Symbols
   3292 ........................................
   3293 
   3294 A special notation is needed for common symbols, because in many object
   3295 file formats common symbols do not have a particular input section.  The
   3296 linker treats common symbols as though they are in an input section
   3297 named `COMMON'.
   3298 
   3299    You may use file names with the `COMMON' section just as with any
   3300 other input sections.  You can use this to place common symbols from a
   3301 particular input file in one section while common symbols from other
   3302 input files are placed in another section.
   3303 
   3304    In most cases, common symbols in input files will be placed in the
   3305 `.bss' section in the output file.  For example:
   3306      .bss { *(.bss) *(COMMON) }
   3307 
   3308    Some object file formats have more than one type of common symbol.
   3309 For example, the MIPS ELF object file format distinguishes standard
   3310 common symbols and small common symbols.  In this case, the linker will
   3311 use a different special section name for other types of common symbols.
   3312 In the case of MIPS ELF, the linker uses `COMMON' for standard common
   3313 symbols and `.scommon' for small common symbols.  This permits you to
   3314 map the different types of common symbols into memory at different
   3315 locations.
   3316 
   3317    You will sometimes see `[COMMON]' in old linker scripts.  This
   3318 notation is now considered obsolete.  It is equivalent to `*(COMMON)'.
   3319 
   3320 
   3321 File: ld.info,  Node: Input Section Keep,  Next: Input Section Example,  Prev: Input Section Common,  Up: Input Section
   3322 
   3323 3.6.4.4 Input Section and Garbage Collection
   3324 ............................................
   3325 
   3326 When link-time garbage collection is in use (`--gc-sections'), it is
   3327 often useful to mark sections that should not be eliminated.  This is
   3328 accomplished by surrounding an input section's wildcard entry with
   3329 `KEEP()', as in `KEEP(*(.init))' or `KEEP(SORT_BY_NAME(*)(.ctors))'.
   3330 
   3331 
   3332 File: ld.info,  Node: Input Section Example,  Prev: Input Section Keep,  Up: Input Section
   3333 
   3334 3.6.4.5 Input Section Example
   3335 .............................
   3336 
   3337 The following example is a complete linker script.  It tells the linker
   3338 to read all of the sections from file `all.o' and place them at the
   3339 start of output section `outputa' which starts at location `0x10000'.
   3340 All of section `.input1' from file `foo.o' follows immediately, in the
   3341 same output section.  All of section `.input2' from `foo.o' goes into
   3342 output section `outputb', followed by section `.input1' from `foo1.o'.
   3343 All of the remaining `.input1' and `.input2' sections from any files
   3344 are written to output section `outputc'.
   3345 
   3346      SECTIONS {
   3347        outputa 0x10000 :
   3348          {
   3349          all.o
   3350          foo.o (.input1)
   3351          }
   3352        outputb :
   3353          {
   3354          foo.o (.input2)
   3355          foo1.o (.input1)
   3356          }
   3357        outputc :
   3358          {
   3359          *(.input1)
   3360          *(.input2)
   3361          }
   3362      }
   3363 
   3364 
   3365 File: ld.info,  Node: Output Section Data,  Next: Output Section Keywords,  Prev: Input Section,  Up: SECTIONS
   3366 
   3367 3.6.5 Output Section Data
   3368 -------------------------
   3369 
   3370 You can include explicit bytes of data in an output section by using
   3371 `BYTE', `SHORT', `LONG', `QUAD', or `SQUAD' as an output section
   3372 command.  Each keyword is followed by an expression in parentheses
   3373 providing the value to store (*note Expressions::).  The value of the
   3374 expression is stored at the current value of the location counter.
   3375 
   3376    The `BYTE', `SHORT', `LONG', and `QUAD' commands store one, two,
   3377 four, and eight bytes (respectively).  After storing the bytes, the
   3378 location counter is incremented by the number of bytes stored.
   3379 
   3380    For example, this will store the byte 1 followed by the four byte
   3381 value of the symbol `addr':
   3382      BYTE(1)
   3383      LONG(addr)
   3384 
   3385    When using a 64 bit host or target, `QUAD' and `SQUAD' are the same;
   3386 they both store an 8 byte, or 64 bit, value.  When both host and target
   3387 are 32 bits, an expression is computed as 32 bits.  In this case `QUAD'
   3388 stores a 32 bit value zero extended to 64 bits, and `SQUAD' stores a 32
   3389 bit value sign extended to 64 bits.
   3390 
   3391    If the object file format of the output file has an explicit
   3392 endianness, which is the normal case, the value will be stored in that
   3393 endianness.  When the object file format does not have an explicit
   3394 endianness, as is true of, for example, S-records, the value will be
   3395 stored in the endianness of the first input object file.
   3396 
   3397    Note--these commands only work inside a section description and not
   3398 between them, so the following will produce an error from the linker:
   3399      SECTIONS { .text : { *(.text) } LONG(1) .data : { *(.data) } }
   3400    whereas this will work:
   3401      SECTIONS { .text : { *(.text) ; LONG(1) } .data : { *(.data) } }
   3402 
   3403    You may use the `FILL' command to set the fill pattern for the
   3404 current section.  It is followed by an expression in parentheses.  Any
   3405 otherwise unspecified regions of memory within the section (for example,
   3406 gaps left due to the required alignment of input sections) are filled
   3407 with the value of the expression, repeated as necessary.  A `FILL'
   3408 statement covers memory locations after the point at which it occurs in
   3409 the section definition; by including more than one `FILL' statement,
   3410 you can have different fill patterns in different parts of an output
   3411 section.
   3412 
   3413    This example shows how to fill unspecified regions of memory with the
   3414 value `0x90':
   3415      FILL(0x90909090)
   3416 
   3417    The `FILL' command is similar to the `=FILLEXP' output section
   3418 attribute, but it only affects the part of the section following the
   3419 `FILL' command, rather than the entire section.  If both are used, the
   3420 `FILL' command takes precedence.  *Note Output Section Fill::, for
   3421 details on the fill expression.
   3422 
   3423 
   3424 File: ld.info,  Node: Output Section Keywords,  Next: Output Section Discarding,  Prev: Output Section Data,  Up: SECTIONS
   3425 
   3426 3.6.6 Output Section Keywords
   3427 -----------------------------
   3428 
   3429 There are a couple of keywords which can appear as output section
   3430 commands.
   3431 
   3432 `CREATE_OBJECT_SYMBOLS'
   3433      The command tells the linker to create a symbol for each input
   3434      file.  The name of each symbol will be the name of the
   3435      corresponding input file.  The section of each symbol will be the
   3436      output section in which the `CREATE_OBJECT_SYMBOLS' command
   3437      appears.
   3438 
   3439      This is conventional for the a.out object file format.  It is not
   3440      normally used for any other object file format.
   3441 
   3442 `CONSTRUCTORS'
   3443      When linking using the a.out object file format, the linker uses an
   3444      unusual set construct to support C++ global constructors and
   3445      destructors.  When linking object file formats which do not support
   3446      arbitrary sections, such as ECOFF and XCOFF, the linker will
   3447      automatically recognize C++ global constructors and destructors by
   3448      name.  For these object file formats, the `CONSTRUCTORS' command
   3449      tells the linker to place constructor information in the output
   3450      section where the `CONSTRUCTORS' command appears.  The
   3451      `CONSTRUCTORS' command is ignored for other object file formats.
   3452 
   3453      The symbol `__CTOR_LIST__' marks the start of the global
   3454      constructors, and the symbol `__CTOR_END__' marks the end.
   3455      Similarly, `__DTOR_LIST__' and `__DTOR_END__' mark the start and
   3456      end of the global destructors.  The first word in the list is the
   3457      number of entries, followed by the address of each constructor or
   3458      destructor, followed by a zero word.  The compiler must arrange to
   3459      actually run the code.  For these object file formats GNU C++
   3460      normally calls constructors from a subroutine `__main'; a call to
   3461      `__main' is automatically inserted into the startup code for
   3462      `main'.  GNU C++ normally runs destructors either by using
   3463      `atexit', or directly from the function `exit'.
   3464 
   3465      For object file formats such as `COFF' or `ELF' which support
   3466      arbitrary section names, GNU C++ will normally arrange to put the
   3467      addresses of global constructors and destructors into the `.ctors'
   3468      and `.dtors' sections.  Placing the following sequence into your
   3469      linker script will build the sort of table which the GNU C++
   3470      runtime code expects to see.
   3471 
   3472                 __CTOR_LIST__ = .;
   3473                 LONG((__CTOR_END__ - __CTOR_LIST__) / 4 - 2)
   3474                 *(.ctors)
   3475                 LONG(0)
   3476                 __CTOR_END__ = .;
   3477                 __DTOR_LIST__ = .;
   3478                 LONG((__DTOR_END__ - __DTOR_LIST__) / 4 - 2)
   3479                 *(.dtors)
   3480                 LONG(0)
   3481                 __DTOR_END__ = .;
   3482 
   3483      If you are using the GNU C++ support for initialization priority,
   3484      which provides some control over the order in which global
   3485      constructors are run, you must sort the constructors at link time
   3486      to ensure that they are executed in the correct order.  When using
   3487      the `CONSTRUCTORS' command, use `SORT_BY_NAME(CONSTRUCTORS)'
   3488      instead.  When using the `.ctors' and `.dtors' sections, use
   3489      `*(SORT_BY_NAME(.ctors))' and `*(SORT_BY_NAME(.dtors))' instead of
   3490      just `*(.ctors)' and `*(.dtors)'.
   3491 
   3492      Normally the compiler and linker will handle these issues
   3493      automatically, and you will not need to concern yourself with
   3494      them.  However, you may need to consider this if you are using C++
   3495      and writing your own linker scripts.
   3496 
   3497 
   3498 
   3499 File: ld.info,  Node: Output Section Discarding,  Next: Output Section Attributes,  Prev: Output Section Keywords,  Up: SECTIONS
   3500 
   3501 3.6.7 Output Section Discarding
   3502 -------------------------------
   3503 
   3504 The linker will not create output sections with no contents.  This is
   3505 for convenience when referring to input sections that may or may not be
   3506 present in any of the input files.  For example:
   3507      .foo : { *(.foo) }
   3508    will only create a `.foo' section in the output file if there is a
   3509 `.foo' section in at least one input file, and if the input sections
   3510 are not all empty.  Other link script directives that allocate space in
   3511 an output section will also create the output section.
   3512 
   3513    The linker will ignore address assignments (*note Output Section
   3514 Address::) on discarded output sections, except when the linker script
   3515 defines symbols in the output section.  In that case the linker will
   3516 obey the address assignments, possibly advancing dot even though the
   3517 section is discarded.
   3518 
   3519    The special output section name `/DISCARD/' may be used to discard
   3520 input sections.  Any input sections which are assigned to an output
   3521 section named `/DISCARD/' are not included in the output file.
   3522 
   3523 
   3524 File: ld.info,  Node: Output Section Attributes,  Next: Overlay Description,  Prev: Output Section Discarding,  Up: SECTIONS
   3525 
   3526 3.6.8 Output Section Attributes
   3527 -------------------------------
   3528 
   3529 We showed above that the full description of an output section looked
   3530 like this:
   3531 
   3532      SECTION [ADDRESS] [(TYPE)] :
   3533        [AT(LMA)]
   3534        [ALIGN(SECTION_ALIGN)]
   3535        [SUBALIGN(SUBSECTION_ALIGN)]
   3536        [CONSTRAINT]
   3537        {
   3538          OUTPUT-SECTION-COMMAND
   3539          OUTPUT-SECTION-COMMAND
   3540          ...
   3541        } [>REGION] [AT>LMA_REGION] [:PHDR :PHDR ...] [=FILLEXP]
   3542 
   3543    We've already described SECTION, ADDRESS, and
   3544 OUTPUT-SECTION-COMMAND.  In this section we will describe the remaining
   3545 section attributes.
   3546 
   3547 * Menu:
   3548 
   3549 * Output Section Type::		Output section type
   3550 * Output Section LMA::		Output section LMA
   3551 * Forced Output Alignment::	Forced Output Alignment
   3552 * Forced Input Alignment::	Forced Input Alignment
   3553 * Output Section Constraint::   Output section constraint
   3554 * Output Section Region::	Output section region
   3555 * Output Section Phdr::		Output section phdr
   3556 * Output Section Fill::		Output section fill
   3557 
   3558 
   3559 File: ld.info,  Node: Output Section Type,  Next: Output Section LMA,  Up: Output Section Attributes
   3560 
   3561 3.6.8.1 Output Section Type
   3562 ...........................
   3563 
   3564 Each output section may have a type.  The type is a keyword in
   3565 parentheses.  The following types are defined:
   3566 
   3567 `NOLOAD'
   3568      The section should be marked as not loadable, so that it will not
   3569      be loaded into memory when the program is run.
   3570 
   3571 `DSECT'
   3572 `COPY'
   3573 `INFO'
   3574 `OVERLAY'
   3575      These type names are supported for backward compatibility, and are
   3576      rarely used.  They all have the same effect: the section should be
   3577      marked as not allocatable, so that no memory is allocated for the
   3578      section when the program is run.
   3579 
   3580    The linker normally sets the attributes of an output section based on
   3581 the input sections which map into it.  You can override this by using
   3582 the section type.  For example, in the script sample below, the `ROM'
   3583 section is addressed at memory location `0' and does not need to be
   3584 loaded when the program is run.
   3585      SECTIONS {
   3586        ROM 0 (NOLOAD) : { ... }
   3587        ...
   3588      }
   3589 
   3590 
   3591 File: ld.info,  Node: Output Section LMA,  Next: Forced Output Alignment,  Prev: Output Section Type,  Up: Output Section Attributes
   3592 
   3593 3.6.8.2 Output Section LMA
   3594 ..........................
   3595 
   3596 Every section has a virtual address (VMA) and a load address (LMA); see
   3597 *note Basic Script Concepts::.  The virtual address is specified by the
   3598 *note Output Section Address:: described earlier.  The load address is
   3599 specified by the `AT' or `AT>' keywords.  Specifying a load address is
   3600 optional.
   3601 
   3602    The `AT' keyword takes an expression as an argument.  This specifies
   3603 the exact load address of the section.  The `AT>' keyword takes the
   3604 name of a memory region as an argument.  *Note MEMORY::.  The load
   3605 address of the section is set to the next free address in the region,
   3606 aligned to the section's alignment requirements.
   3607 
   3608    If neither `AT' nor `AT>' is specified for an allocatable section,
   3609 the linker will use the following heuristic to determine the load
   3610 address:
   3611 
   3612    * If the section has a specific VMA address, then this is used as
   3613      the LMA address as well.
   3614 
   3615    * If the section is not allocatable then its LMA is set to its VMA.
   3616 
   3617    * Otherwise if a memory region can be found that is compatible with
   3618      the current section, and this region contains at least one
   3619      section, then the LMA is set so the difference between the VMA and
   3620      LMA is the same as the difference between the VMA and LMA of the
   3621      last section in the located region.
   3622 
   3623    * If no memory regions have been declared then a default region that
   3624      covers the entire address space is used in the previous step.
   3625 
   3626    * If no suitable region could be found, or there was no previous
   3627      section then the LMA is set equal to the VMA.
   3628 
   3629    This feature is designed to make it easy to build a ROM image.  For
   3630 example, the following linker script creates three output sections: one
   3631 called `.text', which starts at `0x1000', one called `.mdata', which is
   3632 loaded at the end of the `.text' section even though its VMA is
   3633 `0x2000', and one called `.bss' to hold uninitialized data at address
   3634 `0x3000'.  The symbol `_data' is defined with the value `0x2000', which
   3635 shows that the location counter holds the VMA value, not the LMA value.
   3636 
   3637      SECTIONS
   3638        {
   3639        .text 0x1000 : { *(.text) _etext = . ; }
   3640        .mdata 0x2000 :
   3641          AT ( ADDR (.text) + SIZEOF (.text) )
   3642          { _data = . ; *(.data); _edata = . ;  }
   3643        .bss 0x3000 :
   3644          { _bstart = . ;  *(.bss) *(COMMON) ; _bend = . ;}
   3645      }
   3646 
   3647    The run-time initialization code for use with a program generated
   3648 with this linker script would include something like the following, to
   3649 copy the initialized data from the ROM image to its runtime address.
   3650 Notice how this code takes advantage of the symbols defined by the
   3651 linker script.
   3652 
   3653      extern char _etext, _data, _edata, _bstart, _bend;
   3654      char *src = &_etext;
   3655      char *dst = &_data;
   3656 
   3657      /* ROM has data at end of text; copy it.  */
   3658      while (dst < &_edata)
   3659        *dst++ = *src++;
   3660 
   3661      /* Zero bss.  */
   3662      for (dst = &_bstart; dst< &_bend; dst++)
   3663        *dst = 0;
   3664 
   3665 
   3666 File: ld.info,  Node: Forced Output Alignment,  Next: Forced Input Alignment,  Prev: Output Section LMA,  Up: Output Section Attributes
   3667 
   3668 3.6.8.3 Forced Output Alignment
   3669 ...............................
   3670 
   3671 You can increase an output section's alignment by using ALIGN.
   3672 
   3673 
   3674 File: ld.info,  Node: Forced Input Alignment,  Next: Output Section Constraint,  Prev: Forced Output Alignment,  Up: Output Section Attributes
   3675 
   3676 3.6.8.4 Forced Input Alignment
   3677 ..............................
   3678 
   3679 You can force input section alignment within an output section by using
   3680 SUBALIGN.  The value specified overrides any alignment given by input
   3681 sections, whether larger or smaller.
   3682 
   3683 
   3684 File: ld.info,  Node: Output Section Constraint,  Next: Output Section Region,  Prev: Forced Input Alignment,  Up: Output Section Attributes
   3685 
   3686 3.6.8.5 Output Section Constraint
   3687 .................................
   3688 
   3689 You can specify that an output section should only be created if all of
   3690 its input sections are read-only or all of its input sections are
   3691 read-write by using the keyword `ONLY_IF_RO' and `ONLY_IF_RW'
   3692 respectively.
   3693 
   3694 
   3695 File: ld.info,  Node: Output Section Region,  Next: Output Section Phdr,  Prev: Output Section Constraint,  Up: Output Section Attributes
   3696 
   3697 3.6.8.6 Output Section Region
   3698 .............................
   3699 
   3700 You can assign a section to a previously defined region of memory by
   3701 using `>REGION'.  *Note MEMORY::.
   3702 
   3703    Here is a simple example:
   3704      MEMORY { rom : ORIGIN = 0x1000, LENGTH = 0x1000 }
   3705      SECTIONS { ROM : { *(.text) } >rom }
   3706 
   3707 
   3708 File: ld.info,  Node: Output Section Phdr,  Next: Output Section Fill,  Prev: Output Section Region,  Up: Output Section Attributes
   3709 
   3710 3.6.8.7 Output Section Phdr
   3711 ...........................
   3712 
   3713 You can assign a section to a previously defined program segment by
   3714 using `:PHDR'.  *Note PHDRS::.  If a section is assigned to one or more
   3715 segments, then all subsequent allocated sections will be assigned to
   3716 those segments as well, unless they use an explicitly `:PHDR' modifier.
   3717 You can use `:NONE' to tell the linker to not put the section in any
   3718 segment at all.
   3719 
   3720    Here is a simple example:
   3721      PHDRS { text PT_LOAD ; }
   3722      SECTIONS { .text : { *(.text) } :text }
   3723 
   3724 
   3725 File: ld.info,  Node: Output Section Fill,  Prev: Output Section Phdr,  Up: Output Section Attributes
   3726 
   3727 3.6.8.8 Output Section Fill
   3728 ...........................
   3729 
   3730 You can set the fill pattern for an entire section by using `=FILLEXP'.
   3731 FILLEXP is an expression (*note Expressions::).  Any otherwise
   3732 unspecified regions of memory within the output section (for example,
   3733 gaps left due to the required alignment of input sections) will be
   3734 filled with the value, repeated as necessary.  If the fill expression
   3735 is a simple hex number, ie. a string of hex digit starting with `0x'
   3736 and without a trailing `k' or `M', then an arbitrarily long sequence of
   3737 hex digits can be used to specify the fill pattern;  Leading zeros
   3738 become part of the pattern too.  For all other cases, including extra
   3739 parentheses or a unary `+', the fill pattern is the four least
   3740 significant bytes of the value of the expression.  In all cases, the
   3741 number is big-endian.
   3742 
   3743    You can also change the fill value with a `FILL' command in the
   3744 output section commands; (*note Output Section Data::).
   3745 
   3746    Here is a simple example:
   3747      SECTIONS { .text : { *(.text) } =0x90909090 }
   3748 
   3749 
   3750 File: ld.info,  Node: Overlay Description,  Prev: Output Section Attributes,  Up: SECTIONS
   3751 
   3752 3.6.9 Overlay Description
   3753 -------------------------
   3754 
   3755 An overlay description provides an easy way to describe sections which
   3756 are to be loaded as part of a single memory image but are to be run at
   3757 the same memory address.  At run time, some sort of overlay manager will
   3758 copy the overlaid sections in and out of the runtime memory address as
   3759 required, perhaps by simply manipulating addressing bits.  This approach
   3760 can be useful, for example, when a certain region of memory is faster
   3761 than another.
   3762 
   3763    Overlays are described using the `OVERLAY' command.  The `OVERLAY'
   3764 command is used within a `SECTIONS' command, like an output section
   3765 description.  The full syntax of the `OVERLAY' command is as follows:
   3766      OVERLAY [START] : [NOCROSSREFS] [AT ( LDADDR )]
   3767        {
   3768          SECNAME1
   3769            {
   3770              OUTPUT-SECTION-COMMAND
   3771              OUTPUT-SECTION-COMMAND
   3772              ...
   3773            } [:PHDR...] [=FILL]
   3774          SECNAME2
   3775            {
   3776              OUTPUT-SECTION-COMMAND
   3777              OUTPUT-SECTION-COMMAND
   3778              ...
   3779            } [:PHDR...] [=FILL]
   3780          ...
   3781        } [>REGION] [:PHDR...] [=FILL]
   3782 
   3783    Everything is optional except `OVERLAY' (a keyword), and each
   3784 section must have a name (SECNAME1 and SECNAME2 above).  The section
   3785 definitions within the `OVERLAY' construct are identical to those
   3786 within the general `SECTIONS' contruct (*note SECTIONS::), except that
   3787 no addresses and no memory regions may be defined for sections within
   3788 an `OVERLAY'.
   3789 
   3790    The sections are all defined with the same starting address.  The
   3791 load addresses of the sections are arranged such that they are
   3792 consecutive in memory starting at the load address used for the
   3793 `OVERLAY' as a whole (as with normal section definitions, the load
   3794 address is optional, and defaults to the start address; the start
   3795 address is also optional, and defaults to the current value of the
   3796 location counter).
   3797 
   3798    If the `NOCROSSREFS' keyword is used, and there any references among
   3799 the sections, the linker will report an error.  Since the sections all
   3800 run at the same address, it normally does not make sense for one
   3801 section to refer directly to another.  *Note NOCROSSREFS: Miscellaneous
   3802 Commands.
   3803 
   3804    For each section within the `OVERLAY', the linker automatically
   3805 provides two symbols.  The symbol `__load_start_SECNAME' is defined as
   3806 the starting load address of the section.  The symbol
   3807 `__load_stop_SECNAME' is defined as the final load address of the
   3808 section.  Any characters within SECNAME which are not legal within C
   3809 identifiers are removed.  C (or assembler) code may use these symbols
   3810 to move the overlaid sections around as necessary.
   3811 
   3812    At the end of the overlay, the value of the location counter is set
   3813 to the start address of the overlay plus the size of the largest
   3814 section.
   3815 
   3816    Here is an example.  Remember that this would appear inside a
   3817 `SECTIONS' construct.
   3818        OVERLAY 0x1000 : AT (0x4000)
   3819         {
   3820           .text0 { o1/*.o(.text) }
   3821           .text1 { o2/*.o(.text) }
   3822         }
   3823 This will define both `.text0' and `.text1' to start at address 0x1000.
   3824 `.text0' will be loaded at address 0x4000, and `.text1' will be loaded
   3825 immediately after `.text0'.  The following symbols will be defined if
   3826 referenced: `__load_start_text0', `__load_stop_text0',
   3827 `__load_start_text1', `__load_stop_text1'.
   3828 
   3829    C code to copy overlay `.text1' into the overlay area might look
   3830 like the following.
   3831 
   3832        extern char __load_start_text1, __load_stop_text1;
   3833        memcpy ((char *) 0x1000, &__load_start_text1,
   3834                &__load_stop_text1 - &__load_start_text1);
   3835 
   3836    Note that the `OVERLAY' command is just syntactic sugar, since
   3837 everything it does can be done using the more basic commands.  The above
   3838 example could have been written identically as follows.
   3839 
   3840        .text0 0x1000 : AT (0x4000) { o1/*.o(.text) }
   3841        PROVIDE (__load_start_text0 = LOADADDR (.text0));
   3842        PROVIDE (__load_stop_text0 = LOADADDR (.text0) + SIZEOF (.text0));
   3843        .text1 0x1000 : AT (0x4000 + SIZEOF (.text0)) { o2/*.o(.text) }
   3844        PROVIDE (__load_start_text1 = LOADADDR (.text1));
   3845        PROVIDE (__load_stop_text1 = LOADADDR (.text1) + SIZEOF (.text1));
   3846        . = 0x1000 + MAX (SIZEOF (.text0), SIZEOF (.text1));
   3847 
   3848 
   3849 File: ld.info,  Node: MEMORY,  Next: PHDRS,  Prev: SECTIONS,  Up: Scripts
   3850 
   3851 3.7 MEMORY Command
   3852 ==================
   3853 
   3854 The linker's default configuration permits allocation of all available
   3855 memory.  You can override this by using the `MEMORY' command.
   3856 
   3857    The `MEMORY' command describes the location and size of blocks of
   3858 memory in the target.  You can use it to describe which memory regions
   3859 may be used by the linker, and which memory regions it must avoid.  You
   3860 can then assign sections to particular memory regions.  The linker will
   3861 set section addresses based on the memory regions, and will warn about
   3862 regions that become too full.  The linker will not shuffle sections
   3863 around to fit into the available regions.
   3864 
   3865    A linker script may contain at most one use of the `MEMORY' command.
   3866 However, you can define as many blocks of memory within it as you wish.
   3867 The syntax is:
   3868      MEMORY
   3869        {
   3870          NAME [(ATTR)] : ORIGIN = ORIGIN, LENGTH = LEN
   3871          ...
   3872        }
   3873 
   3874    The NAME is a name used in the linker script to refer to the region.
   3875 The region name has no meaning outside of the linker script.  Region
   3876 names are stored in a separate name space, and will not conflict with
   3877 symbol names, file names, or section names.  Each memory region must
   3878 have a distinct name within the `MEMORY' command.  However you can add
   3879 later alias names to existing memory regions with the *note
   3880 REGION_ALIAS:: command.
   3881 
   3882    The ATTR string is an optional list of attributes that specify
   3883 whether to use a particular memory region for an input section which is
   3884 not explicitly mapped in the linker script.  As described in *note
   3885 SECTIONS::, if you do not specify an output section for some input
   3886 section, the linker will create an output section with the same name as
   3887 the input section.  If you define region attributes, the linker will use
   3888 them to select the memory region for the output section that it creates.
   3889 
   3890    The ATTR string must consist only of the following characters:
   3891 `R'
   3892      Read-only section
   3893 
   3894 `W'
   3895      Read/write section
   3896 
   3897 `X'
   3898      Executable section
   3899 
   3900 `A'
   3901      Allocatable section
   3902 
   3903 `I'
   3904      Initialized section
   3905 
   3906 `L'
   3907      Same as `I'
   3908 
   3909 `!'
   3910      Invert the sense of any of the attributes that follow
   3911 
   3912    If a unmapped section matches any of the listed attributes other than
   3913 `!', it will be placed in the memory region.  The `!' attribute
   3914 reverses this test, so that an unmapped section will be placed in the
   3915 memory region only if it does not match any of the listed attributes.
   3916 
   3917    The ORIGIN is an numerical expression for the start address of the
   3918 memory region.  The expression must evaluate to a constant and it
   3919 cannot involve any symbols.  The keyword `ORIGIN' may be abbreviated to
   3920 `org' or `o' (but not, for example, `ORG').
   3921 
   3922    The LEN is an expression for the size in bytes of the memory region.
   3923 As with the ORIGIN expression, the expression must be numerical only
   3924 and must evaluate to a constant.  The keyword `LENGTH' may be
   3925 abbreviated to `len' or `l'.
   3926 
   3927    In the following example, we specify that there are two memory
   3928 regions available for allocation: one starting at `0' for 256 kilobytes,
   3929 and the other starting at `0x40000000' for four megabytes.  The linker
   3930 will place into the `rom' memory region every section which is not
   3931 explicitly mapped into a memory region, and is either read-only or
   3932 executable.  The linker will place other sections which are not
   3933 explicitly mapped into a memory region into the `ram' memory region.
   3934 
   3935      MEMORY
   3936        {
   3937          rom (rx)  : ORIGIN = 0, LENGTH = 256K
   3938          ram (!rx) : org = 0x40000000, l = 4M
   3939        }
   3940 
   3941    Once you define a memory region, you can direct the linker to place
   3942 specific output sections into that memory region by using the `>REGION'
   3943 output section attribute.  For example, if you have a memory region
   3944 named `mem', you would use `>mem' in the output section definition.
   3945 *Note Output Section Region::.  If no address was specified for the
   3946 output section, the linker will set the address to the next available
   3947 address within the memory region.  If the combined output sections
   3948 directed to a memory region are too large for the region, the linker
   3949 will issue an error message.
   3950 
   3951    It is possible to access the origin and length of a memory in an
   3952 expression via the `ORIGIN(MEMORY)' and `LENGTH(MEMORY)' functions:
   3953 
   3954        _fstack = ORIGIN(ram) + LENGTH(ram) - 4;
   3955 
   3956 
   3957 File: ld.info,  Node: PHDRS,  Next: VERSION,  Prev: MEMORY,  Up: Scripts
   3958 
   3959 3.8 PHDRS Command
   3960 =================
   3961 
   3962 The ELF object file format uses "program headers", also knows as
   3963 "segments".  The program headers describe how the program should be
   3964 loaded into memory.  You can print them out by using the `objdump'
   3965 program with the `-p' option.
   3966 
   3967    When you run an ELF program on a native ELF system, the system loader
   3968 reads the program headers in order to figure out how to load the
   3969 program.  This will only work if the program headers are set correctly.
   3970 This manual does not describe the details of how the system loader
   3971 interprets program headers; for more information, see the ELF ABI.
   3972 
   3973    The linker will create reasonable program headers by default.
   3974 However, in some cases, you may need to specify the program headers more
   3975 precisely.  You may use the `PHDRS' command for this purpose.  When the
   3976 linker sees the `PHDRS' command in the linker script, it will not
   3977 create any program headers other than the ones specified.
   3978 
   3979    The linker only pays attention to the `PHDRS' command when
   3980 generating an ELF output file.  In other cases, the linker will simply
   3981 ignore `PHDRS'.
   3982 
   3983    This is the syntax of the `PHDRS' command.  The words `PHDRS',
   3984 `FILEHDR', `AT', and `FLAGS' are keywords.
   3985 
   3986      PHDRS
   3987      {
   3988        NAME TYPE [ FILEHDR ] [ PHDRS ] [ AT ( ADDRESS ) ]
   3989              [ FLAGS ( FLAGS ) ] ;
   3990      }
   3991 
   3992    The NAME is used only for reference in the `SECTIONS' command of the
   3993 linker script.  It is not put into the output file.  Program header
   3994 names are stored in a separate name space, and will not conflict with
   3995 symbol names, file names, or section names.  Each program header must
   3996 have a distinct name.  The headers are processed in order and it is
   3997 usual for them to map to sections in ascending load address order.
   3998 
   3999    Certain program header types describe segments of memory which the
   4000 system loader will load from the file.  In the linker script, you
   4001 specify the contents of these segments by placing allocatable output
   4002 sections in the segments.  You use the `:PHDR' output section attribute
   4003 to place a section in a particular segment.  *Note Output Section
   4004 Phdr::.
   4005 
   4006    It is normal to put certain sections in more than one segment.  This
   4007 merely implies that one segment of memory contains another.  You may
   4008 repeat `:PHDR', using it once for each segment which should contain the
   4009 section.
   4010 
   4011    If you place a section in one or more segments using `:PHDR', then
   4012 the linker will place all subsequent allocatable sections which do not
   4013 specify `:PHDR' in the same segments.  This is for convenience, since
   4014 generally a whole set of contiguous sections will be placed in a single
   4015 segment.  You can use `:NONE' to override the default segment and tell
   4016 the linker to not put the section in any segment at all.
   4017 
   4018    You may use the `FILEHDR' and `PHDRS' keywords after the program
   4019 header type to further describe the contents of the segment.  The
   4020 `FILEHDR' keyword means that the segment should include the ELF file
   4021 header.  The `PHDRS' keyword means that the segment should include the
   4022 ELF program headers themselves.  If applied to a loadable segment
   4023 (`PT_LOAD'), all prior loadable segments must have one of these
   4024 keywords.
   4025 
   4026    The TYPE may be one of the following.  The numbers indicate the
   4027 value of the keyword.
   4028 
   4029 `PT_NULL' (0)
   4030      Indicates an unused program header.
   4031 
   4032 `PT_LOAD' (1)
   4033      Indicates that this program header describes a segment to be
   4034      loaded from the file.
   4035 
   4036 `PT_DYNAMIC' (2)
   4037      Indicates a segment where dynamic linking information can be found.
   4038 
   4039 `PT_INTERP' (3)
   4040      Indicates a segment where the name of the program interpreter may
   4041      be found.
   4042 
   4043 `PT_NOTE' (4)
   4044      Indicates a segment holding note information.
   4045 
   4046 `PT_SHLIB' (5)
   4047      A reserved program header type, defined but not specified by the
   4048      ELF ABI.
   4049 
   4050 `PT_PHDR' (6)
   4051      Indicates a segment where the program headers may be found.
   4052 
   4053 EXPRESSION
   4054      An expression giving the numeric type of the program header.  This
   4055      may be used for types not defined above.
   4056 
   4057    You can specify that a segment should be loaded at a particular
   4058 address in memory by using an `AT' expression.  This is identical to the
   4059 `AT' command used as an output section attribute (*note Output Section
   4060 LMA::).  The `AT' command for a program header overrides the output
   4061 section attribute.
   4062 
   4063    The linker will normally set the segment flags based on the sections
   4064 which comprise the segment.  You may use the `FLAGS' keyword to
   4065 explicitly specify the segment flags.  The value of FLAGS must be an
   4066 integer.  It is used to set the `p_flags' field of the program header.
   4067 
   4068    Here is an example of `PHDRS'.  This shows a typical set of program
   4069 headers used on a native ELF system.
   4070 
   4071      PHDRS
   4072      {
   4073        headers PT_PHDR PHDRS ;
   4074        interp PT_INTERP ;
   4075        text PT_LOAD FILEHDR PHDRS ;
   4076        data PT_LOAD ;
   4077        dynamic PT_DYNAMIC ;
   4078      }
   4079 
   4080      SECTIONS
   4081      {
   4082        . = SIZEOF_HEADERS;
   4083        .interp : { *(.interp) } :text :interp
   4084        .text : { *(.text) } :text
   4085        .rodata : { *(.rodata) } /* defaults to :text */
   4086        ...
   4087        . = . + 0x1000; /* move to a new page in memory */
   4088        .data : { *(.data) } :data
   4089        .dynamic : { *(.dynamic) } :data :dynamic
   4090        ...
   4091      }
   4092 
   4093 
   4094 File: ld.info,  Node: VERSION,  Next: Expressions,  Prev: PHDRS,  Up: Scripts
   4095 
   4096 3.9 VERSION Command
   4097 ===================
   4098 
   4099 The linker supports symbol versions when using ELF.  Symbol versions are
   4100 only useful when using shared libraries.  The dynamic linker can use
   4101 symbol versions to select a specific version of a function when it runs
   4102 a program that may have been linked against an earlier version of the
   4103 shared library.
   4104 
   4105    You can include a version script directly in the main linker script,
   4106 or you can supply the version script as an implicit linker script.  You
   4107 can also use the `--version-script' linker option.
   4108 
   4109    The syntax of the `VERSION' command is simply
   4110      VERSION { version-script-commands }
   4111 
   4112    The format of the version script commands is identical to that used
   4113 by Sun's linker in Solaris 2.5.  The version script defines a tree of
   4114 version nodes.  You specify the node names and interdependencies in the
   4115 version script.  You can specify which symbols are bound to which
   4116 version nodes, and you can reduce a specified set of symbols to local
   4117 scope so that they are not globally visible outside of the shared
   4118 library.
   4119 
   4120    The easiest way to demonstrate the version script language is with a
   4121 few examples.
   4122 
   4123      VERS_1.1 {
   4124      	 global:
   4125      		 foo1;
   4126      	 local:
   4127      		 old*;
   4128      		 original*;
   4129      		 new*;
   4130      };
   4131 
   4132      VERS_1.2 {
   4133      		 foo2;
   4134      } VERS_1.1;
   4135 
   4136      VERS_2.0 {
   4137      		 bar1; bar2;
   4138      	 extern "C++" {
   4139      		 ns::*;
   4140      		 "f(int, double)";
   4141      	 };
   4142      } VERS_1.2;
   4143 
   4144    This example version script defines three version nodes.  The first
   4145 version node defined is `VERS_1.1'; it has no other dependencies.  The
   4146 script binds the symbol `foo1' to `VERS_1.1'.  It reduces a number of
   4147 symbols to local scope so that they are not visible outside of the
   4148 shared library; this is done using wildcard patterns, so that any
   4149 symbol whose name begins with `old', `original', or `new' is matched.
   4150 The wildcard patterns available are the same as those used in the shell
   4151 when matching filenames (also known as "globbing").  However, if you
   4152 specify the symbol name inside double quotes, then the name is treated
   4153 as literal, rather than as a glob pattern.
   4154 
   4155    Next, the version script defines node `VERS_1.2'.  This node depends
   4156 upon `VERS_1.1'.  The script binds the symbol `foo2' to the version
   4157 node `VERS_1.2'.
   4158 
   4159    Finally, the version script defines node `VERS_2.0'.  This node
   4160 depends upon `VERS_1.2'.  The scripts binds the symbols `bar1' and
   4161 `bar2' are bound to the version node `VERS_2.0'.
   4162 
   4163    When the linker finds a symbol defined in a library which is not
   4164 specifically bound to a version node, it will effectively bind it to an
   4165 unspecified base version of the library.  You can bind all otherwise
   4166 unspecified symbols to a given version node by using `global: *;'
   4167 somewhere in the version script.  Note that it's slightly crazy to use
   4168 wildcards in a global spec except on the last version node.  Global
   4169 wildcards elsewhere run the risk of accidentally adding symbols to the
   4170 set exported for an old version.  That's wrong since older versions
   4171 ought to have a fixed set of symbols.
   4172 
   4173    The names of the version nodes have no specific meaning other than
   4174 what they might suggest to the person reading them.  The `2.0' version
   4175 could just as well have appeared in between `1.1' and `1.2'.  However,
   4176 this would be a confusing way to write a version script.
   4177 
   4178    Node name can be omitted, provided it is the only version node in
   4179 the version script.  Such version script doesn't assign any versions to
   4180 symbols, only selects which symbols will be globally visible out and
   4181 which won't.
   4182 
   4183      { global: foo; bar; local: *; };
   4184 
   4185    When you link an application against a shared library that has
   4186 versioned symbols, the application itself knows which version of each
   4187 symbol it requires, and it also knows which version nodes it needs from
   4188 each shared library it is linked against.  Thus at runtime, the dynamic
   4189 loader can make a quick check to make sure that the libraries you have
   4190 linked against do in fact supply all of the version nodes that the
   4191 application will need to resolve all of the dynamic symbols.  In this
   4192 way it is possible for the dynamic linker to know with certainty that
   4193 all external symbols that it needs will be resolvable without having to
   4194 search for each symbol reference.
   4195 
   4196    The symbol versioning is in effect a much more sophisticated way of
   4197 doing minor version checking that SunOS does.  The fundamental problem
   4198 that is being addressed here is that typically references to external
   4199 functions are bound on an as-needed basis, and are not all bound when
   4200 the application starts up.  If a shared library is out of date, a
   4201 required interface may be missing; when the application tries to use
   4202 that interface, it may suddenly and unexpectedly fail.  With symbol
   4203 versioning, the user will get a warning when they start their program if
   4204 the libraries being used with the application are too old.
   4205 
   4206    There are several GNU extensions to Sun's versioning approach.  The
   4207 first of these is the ability to bind a symbol to a version node in the
   4208 source file where the symbol is defined instead of in the versioning
   4209 script.  This was done mainly to reduce the burden on the library
   4210 maintainer.  You can do this by putting something like:
   4211      __asm__(".symver original_foo,foo (a] VERS_1.1");
   4212    in the C source file.  This renames the function `original_foo' to
   4213 be an alias for `foo' bound to the version node `VERS_1.1'.  The
   4214 `local:' directive can be used to prevent the symbol `original_foo'
   4215 from being exported. A `.symver' directive takes precedence over a
   4216 version script.
   4217 
   4218    The second GNU extension is to allow multiple versions of the same
   4219 function to appear in a given shared library.  In this way you can make
   4220 an incompatible change to an interface without increasing the major
   4221 version number of the shared library, while still allowing applications
   4222 linked against the old interface to continue to function.
   4223 
   4224    To do this, you must use multiple `.symver' directives in the source
   4225 file.  Here is an example:
   4226 
   4227      __asm__(".symver original_foo,foo@");
   4228      __asm__(".symver old_foo,foo (a] VERS_1.1");
   4229      __asm__(".symver old_foo1,foo (a] VERS_1.2");
   4230      __asm__(".symver new_foo,foo@@VERS_2.0");
   4231 
   4232    In this example, `foo@' represents the symbol `foo' bound to the
   4233 unspecified base version of the symbol.  The source file that contains
   4234 this example would define 4 C functions: `original_foo', `old_foo',
   4235 `old_foo1', and `new_foo'.
   4236 
   4237    When you have multiple definitions of a given symbol, there needs to
   4238 be some way to specify a default version to which external references to
   4239 this symbol will be bound.  You can do this with the `foo@@VERS_2.0'
   4240 type of `.symver' directive.  You can only declare one version of a
   4241 symbol as the default in this manner; otherwise you would effectively
   4242 have multiple definitions of the same symbol.
   4243 
   4244    If you wish to bind a reference to a specific version of the symbol
   4245 within the shared library, you can use the aliases of convenience
   4246 (i.e., `old_foo'), or you can use the `.symver' directive to
   4247 specifically bind to an external version of the function in question.
   4248 
   4249    You can also specify the language in the version script:
   4250 
   4251      VERSION extern "lang" { version-script-commands }
   4252 
   4253    The supported `lang's are `C', `C++', and `Java'.  The linker will
   4254 iterate over the list of symbols at the link time and demangle them
   4255 according to `lang' before matching them to the patterns specified in
   4256 `version-script-commands'.  The default `lang' is `C'.
   4257 
   4258    Demangled names may contains spaces and other special characters.  As
   4259 described above, you can use a glob pattern to match demangled names,
   4260 or you can use a double-quoted string to match the string exactly.  In
   4261 the latter case, be aware that minor differences (such as differing
   4262 whitespace) between the version script and the demangler output will
   4263 cause a mismatch.  As the exact string generated by the demangler might
   4264 change in the future, even if the mangled name does not, you should
   4265 check that all of your version directives are behaving as you expect
   4266 when you upgrade.
   4267 
   4268 
   4269 File: ld.info,  Node: Expressions,  Next: Implicit Linker Scripts,  Prev: VERSION,  Up: Scripts
   4270 
   4271 3.10 Expressions in Linker Scripts
   4272 ==================================
   4273 
   4274 The syntax for expressions in the linker script language is identical to
   4275 that of C expressions.  All expressions are evaluated as integers.  All
   4276 expressions are evaluated in the same size, which is 32 bits if both the
   4277 host and target are 32 bits, and is otherwise 64 bits.
   4278 
   4279    You can use and set symbol values in expressions.
   4280 
   4281    The linker defines several special purpose builtin functions for use
   4282 in expressions.
   4283 
   4284 * Menu:
   4285 
   4286 * Constants::			Constants
   4287 * Symbolic Constants::          Symbolic constants
   4288 * Symbols::			Symbol Names
   4289 * Orphan Sections::		Orphan Sections
   4290 * Location Counter::		The Location Counter
   4291 * Operators::			Operators
   4292 * Evaluation::			Evaluation
   4293 * Expression Section::		The Section of an Expression
   4294 * Builtin Functions::		Builtin Functions
   4295 
   4296 
   4297 File: ld.info,  Node: Constants,  Next: Symbolic Constants,  Up: Expressions
   4298 
   4299 3.10.1 Constants
   4300 ----------------
   4301 
   4302 All constants are integers.
   4303 
   4304    As in C, the linker considers an integer beginning with `0' to be
   4305 octal, and an integer beginning with `0x' or `0X' to be hexadecimal.
   4306 Alternatively the linker accepts suffixes of `h' or `H' for
   4307 hexadeciaml, `o' or `O' for octal, `b' or `B' for binary and `d' or `D'
   4308 for decimal.  Any integer value without a prefix or a suffix is
   4309 considered to be decimal.
   4310 
   4311    In addition, you can use the suffixes `K' and `M' to scale a
   4312 constant by `1024' or `1024*1024' respectively.  For example, the
   4313 following all refer to the same quantity:
   4314 
   4315      _fourk_1 = 4K;
   4316      _fourk_2 = 4096;
   4317      _fourk_3 = 0x1000;
   4318      _fourk_4 = 10000o;
   4319 
   4320    Note - the `K' and `M' suffixes cannot be used in conjunction with
   4321 the base suffixes mentioned above.
   4322 
   4323 
   4324 File: ld.info,  Node: Symbolic Constants,  Next: Symbols,  Prev: Constants,  Up: Expressions
   4325 
   4326 3.10.2 Symbolic Constants
   4327 -------------------------
   4328 
   4329 It is possible to refer to target specific constants via the use of the
   4330 `CONSTANT(NAME)' operator, where NAME is one of:
   4331 
   4332 `MAXPAGESIZE'
   4333      The target's maximum page size.
   4334 
   4335 `COMMONPAGESIZE'
   4336      The target's default page size.
   4337 
   4338    So for example:
   4339 
   4340        .text ALIGN (CONSTANT (MAXPAGESIZE)) : { *(.text) }
   4341 
   4342    will create a text section aligned to the largest page boundary
   4343 supported by the target.
   4344 
   4345 
   4346 File: ld.info,  Node: Symbols,  Next: Orphan Sections,  Prev: Symbolic Constants,  Up: Expressions
   4347 
   4348 3.10.3 Symbol Names
   4349 -------------------
   4350 
   4351 Unless quoted, symbol names start with a letter, underscore, or period
   4352 and may include letters, digits, underscores, periods, and hyphens.
   4353 Unquoted symbol names must not conflict with any keywords.  You can
   4354 specify a symbol which contains odd characters or has the same name as a
   4355 keyword by surrounding the symbol name in double quotes:
   4356      "SECTION" = 9;
   4357      "with a space" = "also with a space" + 10;
   4358 
   4359    Since symbols can contain many non-alphabetic characters, it is
   4360 safest to delimit symbols with spaces.  For example, `A-B' is one
   4361 symbol, whereas `A - B' is an expression involving subtraction.
   4362 
   4363 
   4364 File: ld.info,  Node: Orphan Sections,  Next: Location Counter,  Prev: Symbols,  Up: Expressions
   4365 
   4366 3.10.4 Orphan Sections
   4367 ----------------------
   4368 
   4369 Orphan sections are sections present in the input files which are not
   4370 explicitly placed into the output file by the linker script.  The
   4371 linker will still copy these sections into the output file, but it has
   4372 to guess as to where they should be placed.  The linker uses a simple
   4373 heuristic to do this.  It attempts to place orphan sections after
   4374 non-orphan sections of the same attribute, such as code vs data,
   4375 loadable vs non-loadable, etc.  If there is not enough room to do this
   4376 then it places at the end of the file.
   4377 
   4378    For ELF targets, the attribute of the section includes section type
   4379 as well as section flag.
   4380 
   4381    If an orphaned section's name is representable as a C identifier then
   4382 the linker will automatically *note PROVIDE:: two symbols:
   4383 __start_SECNAME and __end_SECNAME, where SECNAME is the name of the
   4384 section.  These indicate the start address and end address of the
   4385 orphaned section respectively.  Note: most section names are not
   4386 representable as C identifiers because they contain a `.' character.
   4387 
   4388 
   4389 File: ld.info,  Node: Location Counter,  Next: Operators,  Prev: Orphan Sections,  Up: Expressions
   4390 
   4391 3.10.5 The Location Counter
   4392 ---------------------------
   4393 
   4394 The special linker variable "dot" `.' always contains the current
   4395 output location counter.  Since the `.' always refers to a location in
   4396 an output section, it may only appear in an expression within a
   4397 `SECTIONS' command.  The `.' symbol may appear anywhere that an
   4398 ordinary symbol is allowed in an expression.
   4399 
   4400    Assigning a value to `.' will cause the location counter to be
   4401 moved.  This may be used to create holes in the output section.  The
   4402 location counter may not be moved backwards inside an output section,
   4403 and may not be moved backwards outside of an output section if so doing
   4404 creates areas with overlapping LMAs.
   4405 
   4406      SECTIONS
   4407      {
   4408        output :
   4409          {
   4410            file1(.text)
   4411            . = . + 1000;
   4412            file2(.text)
   4413            . += 1000;
   4414            file3(.text)
   4415          } = 0x12345678;
   4416      }
   4417    In the previous example, the `.text' section from `file1' is located
   4418 at the beginning of the output section `output'.  It is followed by a
   4419 1000 byte gap.  Then the `.text' section from `file2' appears, also
   4420 with a 1000 byte gap following before the `.text' section from `file3'.
   4421 The notation `= 0x12345678' specifies what data to write in the gaps
   4422 (*note Output Section Fill::).
   4423 
   4424    Note: `.' actually refers to the byte offset from the start of the
   4425 current containing object.  Normally this is the `SECTIONS' statement,
   4426 whose start address is 0, hence `.' can be used as an absolute address.
   4427 If `.' is used inside a section description however, it refers to the
   4428 byte offset from the start of that section, not an absolute address.
   4429 Thus in a script like this:
   4430 
   4431      SECTIONS
   4432      {
   4433          . = 0x100
   4434          .text: {
   4435            *(.text)
   4436            . = 0x200
   4437          }
   4438          . = 0x500
   4439          .data: {
   4440            *(.data)
   4441            . += 0x600
   4442          }
   4443      }
   4444 
   4445    The `.text' section will be assigned a starting address of 0x100 and
   4446 a size of exactly 0x200 bytes, even if there is not enough data in the
   4447 `.text' input sections to fill this area.  (If there is too much data,
   4448 an error will be produced because this would be an attempt to move `.'
   4449 backwards).  The `.data' section will start at 0x500 and it will have
   4450 an extra 0x600 bytes worth of space after the end of the values from
   4451 the `.data' input sections and before the end of the `.data' output
   4452 section itself.
   4453 
   4454    Setting symbols to the value of the location counter outside of an
   4455 output section statement can result in unexpected values if the linker
   4456 needs to place orphan sections.  For example, given the following:
   4457 
   4458      SECTIONS
   4459      {
   4460          start_of_text = . ;
   4461          .text: { *(.text) }
   4462          end_of_text = . ;
   4463 
   4464          start_of_data = . ;
   4465          .data: { *(.data) }
   4466          end_of_data = . ;
   4467      }
   4468 
   4469    If the linker needs to place some input section, e.g. `.rodata', not
   4470 mentioned in the script, it might choose to place that section between
   4471 `.text' and `.data'.  You might think the linker should place `.rodata'
   4472 on the blank line in the above script, but blank lines are of no
   4473 particular significance to the linker.  As well, the linker doesn't
   4474 associate the above symbol names with their sections.  Instead, it
   4475 assumes that all assignments or other statements belong to the previous
   4476 output section, except for the special case of an assignment to `.'.
   4477 I.e., the linker will place the orphan `.rodata' section as if the
   4478 script was written as follows:
   4479 
   4480      SECTIONS
   4481      {
   4482          start_of_text = . ;
   4483          .text: { *(.text) }
   4484          end_of_text = . ;
   4485 
   4486          start_of_data = . ;
   4487          .rodata: { *(.rodata) }
   4488          .data: { *(.data) }
   4489          end_of_data = . ;
   4490      }
   4491 
   4492    This may or may not be the script author's intention for the value of
   4493 `start_of_data'.  One way to influence the orphan section placement is
   4494 to assign the location counter to itself, as the linker assumes that an
   4495 assignment to `.' is setting the start address of a following output
   4496 section and thus should be grouped with that section.  So you could
   4497 write:
   4498 
   4499      SECTIONS
   4500      {
   4501          start_of_text = . ;
   4502          .text: { *(.text) }
   4503          end_of_text = . ;
   4504 
   4505          . = . ;
   4506          start_of_data = . ;
   4507          .data: { *(.data) }
   4508          end_of_data = . ;
   4509      }
   4510 
   4511    Now, the orphan `.rodata' section will be placed between
   4512 `end_of_text' and `start_of_data'.
   4513 
   4514 
   4515 File: ld.info,  Node: Operators,  Next: Evaluation,  Prev: Location Counter,  Up: Expressions
   4516 
   4517 3.10.6 Operators
   4518 ----------------
   4519 
   4520 The linker recognizes the standard C set of arithmetic operators, with
   4521 the standard bindings and precedence levels:
   4522      precedence      associativity   Operators                Notes
   4523      (highest)
   4524      1               left            !  -  ~                  (1)
   4525      2               left            *  /  %
   4526      3               left            +  -
   4527      4               left            >>  <<
   4528      5               left            ==  !=  >  <  <=  >=
   4529      6               left            &
   4530      7               left            |
   4531      8               left            &&
   4532      9               left            ||
   4533      10              right           ? :
   4534      11              right           &=  +=  -=  *=  /=       (2)
   4535      (lowest)
   4536    Notes: (1) Prefix operators (2) *Note Assignments::.
   4537 
   4538 
   4539 File: ld.info,  Node: Evaluation,  Next: Expression Section,  Prev: Operators,  Up: Expressions
   4540 
   4541 3.10.7 Evaluation
   4542 -----------------
   4543 
   4544 The linker evaluates expressions lazily.  It only computes the value of
   4545 an expression when absolutely necessary.
   4546 
   4547    The linker needs some information, such as the value of the start
   4548 address of the first section, and the origins and lengths of memory
   4549 regions, in order to do any linking at all.  These values are computed
   4550 as soon as possible when the linker reads in the linker script.
   4551 
   4552    However, other values (such as symbol values) are not known or needed
   4553 until after storage allocation.  Such values are evaluated later, when
   4554 other information (such as the sizes of output sections) is available
   4555 for use in the symbol assignment expression.
   4556 
   4557    The sizes of sections cannot be known until after allocation, so
   4558 assignments dependent upon these are not performed until after
   4559 allocation.
   4560 
   4561    Some expressions, such as those depending upon the location counter
   4562 `.', must be evaluated during section allocation.
   4563 
   4564    If the result of an expression is required, but the value is not
   4565 available, then an error results.  For example, a script like the
   4566 following
   4567      SECTIONS
   4568        {
   4569          .text 9+this_isnt_constant :
   4570            { *(.text) }
   4571        }
   4572 will cause the error message `non constant expression for initial
   4573 address'.
   4574 
   4575 
   4576 File: ld.info,  Node: Expression Section,  Next: Builtin Functions,  Prev: Evaluation,  Up: Expressions
   4577 
   4578 3.10.8 The Section of an Expression
   4579 -----------------------------------
   4580 
   4581 Addresses and symbols may be section relative, or absolute.  A section
   4582 relative symbol is relocatable.  If you request relocatable output
   4583 using the `-r' option, a further link operation may change the value of
   4584 a section relative symbol.  On the other hand, an absolute symbol will
   4585 retain the same value throughout any further link operations.
   4586 
   4587    Some terms in linker expressions are addresses.  This is true of
   4588 section relative symbols and for builtin functions that return an
   4589 address, such as `ADDR', `LOADADDR', `ORIGIN' and `SEGMENT_START'.
   4590 Other terms are simply numbers, or are builtin functions that return a
   4591 non-address value, such as `LENGTH'.
   4592 
   4593    When the linker evaluates an expression, the result depends on where
   4594 the expression is located in a linker script.  Expressions appearing
   4595 outside an output section definitions are evaluated with all terms
   4596 first being converted to absolute addresses before applying operators,
   4597 and evaluate to an absolute address result.  Expressions appearing
   4598 inside an output section definition are evaluated with more complex
   4599 rules, but the aim is to treat terms as relative addresses and produce
   4600 a relative address result.  In particular, an assignment of a number to
   4601 a symbol results in a symbol relative to the output section with an
   4602 offset given by the number.  So, in the following simple example,
   4603 
   4604      SECTIONS
   4605        {
   4606          . = 0x100;
   4607          __executable_start = 0x100;
   4608          .data :
   4609          {
   4610            . = 0x10;
   4611            __data_start = 0x10;
   4612            *(.data)
   4613          }
   4614          ...
   4615        }
   4616 
   4617    both `.' and `__executable_start' are set to the absolute address
   4618 0x100 in the first two assignments, then both `.' and `__data_start'
   4619 are set to 0x10 relative to the `.data' section in the second two
   4620 assignments.
   4621 
   4622    For expressions appearing inside an output section definition
   4623 involving numbers, relative addresses and absolute addresses, ld
   4624 follows these rules to evaluate terms:
   4625 
   4626    * Unary operations on a relative address, and binary operations on
   4627      two relative addresses in the same section or between one relative
   4628      address and a number, apply the operator to the offset part of the
   4629      address(es).
   4630 
   4631    * Unary operations on an absolute address, and binary operations on
   4632      one or more absolute addresses or on two relative addresses not in
   4633      the same section, first convert any non-absolute term to an
   4634      absolute address before applying the operator.
   4635 
   4636    The result section of each sub-expression is as follows:
   4637 
   4638    * An operation involving only numbers results in a number.
   4639 
   4640    * The result of comparisons, `&&' and `||' is also a number.
   4641 
   4642    * The result of other operations on relative addresses (after above
   4643      conversions) is a relative address in the same section as the
   4644      operand(s).
   4645 
   4646    * The result of other operations on absolute addresses (after above
   4647      conversions) is an absolute address.
   4648 
   4649    You can use the builtin function `ABSOLUTE' to force an expression
   4650 to be absolute when it would otherwise be relative.  For example, to
   4651 create an absolute symbol set to the address of the end of the output
   4652 section `.data':
   4653      SECTIONS
   4654        {
   4655          .data : { *(.data) _edata = ABSOLUTE(.); }
   4656        }
   4657    If `ABSOLUTE' were not used, `_edata' would be relative to the
   4658 `.data' section.
   4659 
   4660    Using `LOADADDR' also forces an expression absolute, since this
   4661 particular builtin function returns an absolute address.
   4662 
   4663 
   4664 File: ld.info,  Node: Builtin Functions,  Prev: Expression Section,  Up: Expressions
   4665 
   4666 3.10.9 Builtin Functions
   4667 ------------------------
   4668 
   4669 The linker script language includes a number of builtin functions for
   4670 use in linker script expressions.
   4671 
   4672 `ABSOLUTE(EXP)'
   4673      Return the absolute (non-relocatable, as opposed to non-negative)
   4674      value of the expression EXP.  Primarily useful to assign an
   4675      absolute value to a symbol within a section definition, where
   4676      symbol values are normally section relative.  *Note Expression
   4677      Section::.
   4678 
   4679 `ADDR(SECTION)'
   4680      Return the address (VMA) of the named SECTION.  Your script must
   4681      previously have defined the location of that section.  In the
   4682      following example, `start_of_output_1', `symbol_1' and `symbol_2'
   4683      are assigned equivalent values, except that `symbol_1' will be
   4684      relative to the `.output1' section while the other two will be
   4685      absolute:
   4686           SECTIONS { ...
   4687             .output1 :
   4688               {
   4689               start_of_output_1 = ABSOLUTE(.);
   4690               ...
   4691               }
   4692             .output :
   4693               {
   4694               symbol_1 = ADDR(.output1);
   4695               symbol_2 = start_of_output_1;
   4696               }
   4697           ... }
   4698 
   4699 `ALIGN(ALIGN)'
   4700 `ALIGN(EXP,ALIGN)'
   4701      Return the location counter (`.') or arbitrary expression aligned
   4702      to the next ALIGN boundary.  The single operand `ALIGN' doesn't
   4703      change the value of the location counter--it just does arithmetic
   4704      on it.  The two operand `ALIGN' allows an arbitrary expression to
   4705      be aligned upwards (`ALIGN(ALIGN)' is equivalent to `ALIGN(.,
   4706      ALIGN)').
   4707 
   4708      Here is an example which aligns the output `.data' section to the
   4709      next `0x2000' byte boundary after the preceding section and sets a
   4710      variable within the section to the next `0x8000' boundary after the
   4711      input sections:
   4712           SECTIONS { ...
   4713             .data ALIGN(0x2000): {
   4714               *(.data)
   4715               variable = ALIGN(0x8000);
   4716             }
   4717           ... }
   4718      The first use of `ALIGN' in this example specifies the location of
   4719      a section because it is used as the optional ADDRESS attribute of
   4720      a section definition (*note Output Section Address::).  The second
   4721      use of `ALIGN' is used to defines the value of a symbol.
   4722 
   4723      The builtin function `NEXT' is closely related to `ALIGN'.
   4724 
   4725 `ALIGNOF(SECTION)'
   4726      Return the alignment in bytes of the named SECTION, if that
   4727      section has been allocated.  If the section has not been allocated
   4728      when this is evaluated, the linker will report an error. In the
   4729      following example, the alignment of the `.output' section is
   4730      stored as the first value in that section.
   4731           SECTIONS{ ...
   4732             .output {
   4733               LONG (ALIGNOF (.output))
   4734               ...
   4735               }
   4736           ... }
   4737 
   4738 `BLOCK(EXP)'
   4739      This is a synonym for `ALIGN', for compatibility with older linker
   4740      scripts.  It is most often seen when setting the address of an
   4741      output section.
   4742 
   4743 `DATA_SEGMENT_ALIGN(MAXPAGESIZE, COMMONPAGESIZE)'
   4744      This is equivalent to either
   4745           (ALIGN(MAXPAGESIZE) + (. & (MAXPAGESIZE - 1)))
   4746      or
   4747           (ALIGN(MAXPAGESIZE) + (. & (MAXPAGESIZE - COMMONPAGESIZE)))
   4748      depending on whether the latter uses fewer COMMONPAGESIZE sized
   4749      pages for the data segment (area between the result of this
   4750      expression and `DATA_SEGMENT_END') than the former or not.  If the
   4751      latter form is used, it means COMMONPAGESIZE bytes of runtime
   4752      memory will be saved at the expense of up to COMMONPAGESIZE wasted
   4753      bytes in the on-disk file.
   4754 
   4755      This expression can only be used directly in `SECTIONS' commands,
   4756      not in any output section descriptions and only once in the linker
   4757      script.  COMMONPAGESIZE should be less or equal to MAXPAGESIZE and
   4758      should be the system page size the object wants to be optimized
   4759      for (while still working on system page sizes up to MAXPAGESIZE).
   4760 
   4761      Example:
   4762             . = DATA_SEGMENT_ALIGN(0x10000, 0x2000);
   4763 
   4764 `DATA_SEGMENT_END(EXP)'
   4765      This defines the end of data segment for `DATA_SEGMENT_ALIGN'
   4766      evaluation purposes.
   4767 
   4768             . = DATA_SEGMENT_END(.);
   4769 
   4770 `DATA_SEGMENT_RELRO_END(OFFSET, EXP)'
   4771      This defines the end of the `PT_GNU_RELRO' segment when `-z relro'
   4772      option is used.  Second argument is returned.  When `-z relro'
   4773      option is not present, `DATA_SEGMENT_RELRO_END' does nothing,
   4774      otherwise `DATA_SEGMENT_ALIGN' is padded so that EXP + OFFSET is
   4775      aligned to the most commonly used page boundary for particular
   4776      target.  If present in the linker script, it must always come in
   4777      between `DATA_SEGMENT_ALIGN' and `DATA_SEGMENT_END'.
   4778 
   4779             . = DATA_SEGMENT_RELRO_END(24, .);
   4780 
   4781 `DEFINED(SYMBOL)'
   4782      Return 1 if SYMBOL is in the linker global symbol table and is
   4783      defined before the statement using DEFINED in the script, otherwise
   4784      return 0.  You can use this function to provide default values for
   4785      symbols.  For example, the following script fragment shows how to
   4786      set a global symbol `begin' to the first location in the `.text'
   4787      section--but if a symbol called `begin' already existed, its value
   4788      is preserved:
   4789 
   4790           SECTIONS { ...
   4791             .text : {
   4792               begin = DEFINED(begin) ? begin : . ;
   4793               ...
   4794             }
   4795             ...
   4796           }
   4797 
   4798 `LENGTH(MEMORY)'
   4799      Return the length of the memory region named MEMORY.
   4800 
   4801 `LOADADDR(SECTION)'
   4802      Return the absolute LMA of the named SECTION.  (*note Output
   4803      Section LMA::).
   4804 
   4805 `MAX(EXP1, EXP2)'
   4806      Returns the maximum of EXP1 and EXP2.
   4807 
   4808 `MIN(EXP1, EXP2)'
   4809      Returns the minimum of EXP1 and EXP2.
   4810 
   4811 `NEXT(EXP)'
   4812      Return the next unallocated address that is a multiple of EXP.
   4813      This function is closely related to `ALIGN(EXP)'; unless you use
   4814      the `MEMORY' command to define discontinuous memory for the output
   4815      file, the two functions are equivalent.
   4816 
   4817 `ORIGIN(MEMORY)'
   4818      Return the origin of the memory region named MEMORY.
   4819 
   4820 `SEGMENT_START(SEGMENT, DEFAULT)'
   4821      Return the base address of the named SEGMENT.  If an explicit
   4822      value has been given for this segment (with a command-line `-T'
   4823      option) that value will be returned; otherwise the value will be
   4824      DEFAULT.  At present, the `-T' command-line option can only be
   4825      used to set the base address for the "text", "data", and "bss"
   4826      sections, but you can use `SEGMENT_START' with any segment name.
   4827 
   4828 `SIZEOF(SECTION)'
   4829      Return the size in bytes of the named SECTION, if that section has
   4830      been allocated.  If the section has not been allocated when this is
   4831      evaluated, the linker will report an error.  In the following
   4832      example, `symbol_1' and `symbol_2' are assigned identical values:
   4833           SECTIONS{ ...
   4834             .output {
   4835               .start = . ;
   4836               ...
   4837               .end = . ;
   4838               }
   4839             symbol_1 = .end - .start ;
   4840             symbol_2 = SIZEOF(.output);
   4841           ... }
   4842 
   4843 `SIZEOF_HEADERS'
   4844 `sizeof_headers'
   4845      Return the size in bytes of the output file's headers.  This is
   4846      information which appears at the start of the output file.  You
   4847      can use this number when setting the start address of the first
   4848      section, if you choose, to facilitate paging.
   4849 
   4850      When producing an ELF output file, if the linker script uses the
   4851      `SIZEOF_HEADERS' builtin function, the linker must compute the
   4852      number of program headers before it has determined all the section
   4853      addresses and sizes.  If the linker later discovers that it needs
   4854      additional program headers, it will report an error `not enough
   4855      room for program headers'.  To avoid this error, you must avoid
   4856      using the `SIZEOF_HEADERS' function, or you must rework your linker
   4857      script to avoid forcing the linker to use additional program
   4858      headers, or you must define the program headers yourself using the
   4859      `PHDRS' command (*note PHDRS::).
   4860 
   4861 
   4862 File: ld.info,  Node: Implicit Linker Scripts,  Prev: Expressions,  Up: Scripts
   4863 
   4864 3.11 Implicit Linker Scripts
   4865 ============================
   4866 
   4867 If you specify a linker input file which the linker can not recognize as
   4868 an object file or an archive file, it will try to read the file as a
   4869 linker script.  If the file can not be parsed as a linker script, the
   4870 linker will report an error.
   4871 
   4872    An implicit linker script will not replace the default linker script.
   4873 
   4874    Typically an implicit linker script would contain only symbol
   4875 assignments, or the `INPUT', `GROUP', or `VERSION' commands.
   4876 
   4877    Any input files read because of an implicit linker script will be
   4878 read at the position in the command line where the implicit linker
   4879 script was read.  This can affect archive searching.
   4880 
   4881 
   4882 File: ld.info,  Node: Machine Dependent,  Next: BFD,  Prev: Scripts,  Up: Top
   4883 
   4884 4 Machine Dependent Features
   4885 ****************************
   4886 
   4887 `ld' has additional features on some platforms; the following sections
   4888 describe them.  Machines where `ld' has no additional functionality are
   4889 not listed.
   4890 
   4891 * Menu:
   4892 
   4893 
   4894 * H8/300::                      `ld' and the H8/300
   4895 
   4896 * i960::                        `ld' and the Intel 960 family
   4897 
   4898 * ARM::				`ld' and the ARM family
   4899 
   4900 * HPPA ELF32::                  `ld' and HPPA 32-bit ELF
   4901 
   4902 * M68K::			`ld' and the Motorola 68K family
   4903 
   4904 * MMIX::			`ld' and MMIX
   4905 
   4906 * MSP430::			`ld' and MSP430
   4907 
   4908 * M68HC11/68HC12::		`ld' and the Motorola 68HC11 and 68HC12 families
   4909 
   4910 * PowerPC ELF32::		`ld' and PowerPC 32-bit ELF Support
   4911 
   4912 * PowerPC64 ELF64::		`ld' and PowerPC64 64-bit ELF Support
   4913 
   4914 * SPU ELF::			`ld' and SPU ELF Support
   4915 
   4916 * TI COFF::                     `ld' and TI COFF
   4917 
   4918 * WIN32::                       `ld' and WIN32 (cygwin/mingw)
   4919 
   4920 * Xtensa::                      `ld' and Xtensa Processors
   4921 
   4922 
   4923 File: ld.info,  Node: H8/300,  Next: i960,  Up: Machine Dependent
   4924 
   4925 4.1 `ld' and the H8/300
   4926 =======================
   4927 
   4928 For the H8/300, `ld' can perform these global optimizations when you
   4929 specify the `--relax' command-line option.
   4930 
   4931 _relaxing address modes_
   4932      `ld' finds all `jsr' and `jmp' instructions whose targets are
   4933      within eight bits, and turns them into eight-bit program-counter
   4934      relative `bsr' and `bra' instructions, respectively.
   4935 
   4936 _synthesizing instructions_
   4937      `ld' finds all `mov.b' instructions which use the sixteen-bit
   4938      absolute address form, but refer to the top page of memory, and
   4939      changes them to use the eight-bit address form.  (That is: the
   4940      linker turns `mov.b `@'AA:16' into `mov.b `@'AA:8' whenever the
   4941      address AA is in the top page of memory).
   4942 
   4943 _bit manipulation instructions_
   4944      `ld' finds all bit manipulation instructions like `band, bclr,
   4945      biand, bild, bior, bist, bixor, bld, bnot, bor, bset, bst, btst,
   4946      bxor' which use 32 bit and 16 bit absolute address form, but refer
   4947      to the top page of memory, and changes them to use the 8 bit
   4948      address form.  (That is: the linker turns `bset #xx:3,`@'AA:32'
   4949      into `bset #xx:3,`@'AA:8' whenever the address AA is in the top
   4950      page of memory).
   4951 
   4952 _system control instructions_
   4953      `ld' finds all `ldc.w, stc.w' instructions which use the 32 bit
   4954      absolute address form, but refer to the top page of memory, and
   4955      changes them to use 16 bit address form.  (That is: the linker
   4956      turns `ldc.w `@'AA:32,ccr' into `ldc.w `@'AA:16,ccr' whenever the
   4957      address AA is in the top page of memory).
   4958 
   4959 
   4960 File: ld.info,  Node: i960,  Next: ARM,  Prev: H8/300,  Up: Machine Dependent
   4961 
   4962 4.2 `ld' and the Intel 960 Family
   4963 =================================
   4964 
   4965 You can use the `-AARCHITECTURE' command line option to specify one of
   4966 the two-letter names identifying members of the 960 family; the option
   4967 specifies the desired output target, and warns of any incompatible
   4968 instructions in the input files.  It also modifies the linker's search
   4969 strategy for archive libraries, to support the use of libraries
   4970 specific to each particular architecture, by including in the search
   4971 loop names suffixed with the string identifying the architecture.
   4972 
   4973    For example, if your `ld' command line included `-ACA' as well as
   4974 `-ltry', the linker would look (in its built-in search paths, and in
   4975 any paths you specify with `-L') for a library with the names
   4976 
   4977      try
   4978      libtry.a
   4979      tryca
   4980      libtryca.a
   4981 
   4982 The first two possibilities would be considered in any event; the last
   4983 two are due to the use of `-ACA'.
   4984 
   4985    You can meaningfully use `-A' more than once on a command line, since
   4986 the 960 architecture family allows combination of target architectures;
   4987 each use will add another pair of name variants to search for when `-l'
   4988 specifies a library.
   4989 
   4990    `ld' supports the `--relax' option for the i960 family.  If you
   4991 specify `--relax', `ld' finds all `balx' and `calx' instructions whose
   4992 targets are within 24 bits, and turns them into 24-bit program-counter
   4993 relative `bal' and `cal' instructions, respectively.  `ld' also turns
   4994 `cal' instructions into `bal' instructions when it determines that the
   4995 target subroutine is a leaf routine (that is, the target subroutine does
   4996 not itself call any subroutines).
   4997 
   4998    The `--fix-cortex-a8' switch enables a link-time workaround for an
   4999 erratum in certain Cortex-A8 processors.  The workaround is enabled by
   5000 default if you are targeting the ARM v7-A architecture profile.  It can
   5001 be enabled otherwise by specifying `--fix-cortex-a8', or disabled
   5002 unconditionally by specifying `--no-fix-cortex-a8'.
   5003 
   5004    The erratum only affects Thumb-2 code.  Please contact ARM for
   5005 further details.
   5006 
   5007    The `--no-merge-exidx-entries' switch disables the merging of
   5008 adjacent exidx entries in debuginfo.
   5009 
   5010 
   5011 File: ld.info,  Node: M68HC11/68HC12,  Next: PowerPC ELF32,  Prev: MSP430,  Up: Machine Dependent
   5012 
   5013 4.3 `ld' and the Motorola 68HC11 and 68HC12 families
   5014 ====================================================
   5015 
   5016 4.3.1 Linker Relaxation
   5017 -----------------------
   5018 
   5019 For the Motorola 68HC11, `ld' can perform these global optimizations
   5020 when you specify the `--relax' command-line option.
   5021 
   5022 _relaxing address modes_
   5023      `ld' finds all `jsr' and `jmp' instructions whose targets are
   5024      within eight bits, and turns them into eight-bit program-counter
   5025      relative `bsr' and `bra' instructions, respectively.
   5026 
   5027      `ld' also looks at all 16-bit extended addressing modes and
   5028      transforms them in a direct addressing mode when the address is in
   5029      page 0 (between 0 and 0x0ff).
   5030 
   5031 _relaxing gcc instruction group_
   5032      When `gcc' is called with `-mrelax', it can emit group of
   5033      instructions that the linker can optimize to use a 68HC11 direct
   5034      addressing mode. These instructions consists of `bclr' or `bset'
   5035      instructions.
   5036 
   5037 
   5038 4.3.2 Trampoline Generation
   5039 ---------------------------
   5040 
   5041 For 68HC11 and 68HC12, `ld' can generate trampoline code to call a far
   5042 function using a normal `jsr' instruction. The linker will also change
   5043 the relocation to some far function to use the trampoline address
   5044 instead of the function address. This is typically the case when a
   5045 pointer to a function is taken. The pointer will in fact point to the
   5046 function trampoline.
   5047 
   5048 
   5049 File: ld.info,  Node: ARM,  Next: HPPA ELF32,  Prev: i960,  Up: Machine Dependent
   5050 
   5051 4.4 `ld' and the ARM family
   5052 ===========================
   5053 
   5054 For the ARM, `ld' will generate code stubs to allow functions calls
   5055 between ARM and Thumb code.  These stubs only work with code that has
   5056 been compiled and assembled with the `-mthumb-interwork' command line
   5057 option.  If it is necessary to link with old ARM object files or
   5058 libraries, which have not been compiled with the -mthumb-interwork
   5059 option then the `--support-old-code' command line switch should be
   5060 given to the linker.  This will make it generate larger stub functions
   5061 which will work with non-interworking aware ARM code.  Note, however,
   5062 the linker does not support generating stubs for function calls to
   5063 non-interworking aware Thumb code.
   5064 
   5065    The `--thumb-entry' switch is a duplicate of the generic `--entry'
   5066 switch, in that it sets the program's starting address.  But it also
   5067 sets the bottom bit of the address, so that it can be branched to using
   5068 a BX instruction, and the program will start executing in Thumb mode
   5069 straight away.
   5070 
   5071    The `--use-nul-prefixed-import-tables' switch is specifying, that
   5072 the import tables idata4 and idata5 have to be generated with a zero
   5073 elememt prefix for import libraries. This is the old style to generate
   5074 import tables. By default this option is turned off.
   5075 
   5076    The `--be8' switch instructs `ld' to generate BE8 format
   5077 executables.  This option is only valid when linking big-endian objects.
   5078 The resulting image will contain big-endian data and little-endian code.
   5079 
   5080    The `R_ARM_TARGET1' relocation is typically used for entries in the
   5081 `.init_array' section.  It is interpreted as either `R_ARM_REL32' or
   5082 `R_ARM_ABS32', depending on the target.  The `--target1-rel' and
   5083 `--target1-abs' switches override the default.
   5084 
   5085    The `--target2=type' switch overrides the default definition of the
   5086 `R_ARM_TARGET2' relocation.  Valid values for `type', their meanings,
   5087 and target defaults are as follows:
   5088 `rel'
   5089      `R_ARM_REL32' (arm*-*-elf, arm*-*-eabi)
   5090 
   5091 `abs'
   5092      `R_ARM_ABS32' (arm*-*-symbianelf)
   5093 
   5094 `got-rel'
   5095      `R_ARM_GOT_PREL' (arm*-*-linux, arm*-*-*bsd)
   5096 
   5097    The `R_ARM_V4BX' relocation (defined by the ARM AAELF specification)
   5098 enables objects compiled for the ARMv4 architecture to be
   5099 interworking-safe when linked with other objects compiled for ARMv4t,
   5100 but also allows pure ARMv4 binaries to be built from the same ARMv4
   5101 objects.
   5102 
   5103    In the latter case, the switch `--fix-v4bx' must be passed to the
   5104 linker, which causes v4t `BX rM' instructions to be rewritten as `MOV
   5105 PC,rM', since v4 processors do not have a `BX' instruction.
   5106 
   5107    In the former case, the switch should not be used, and `R_ARM_V4BX'
   5108 relocations are ignored.
   5109 
   5110    Replace `BX rM' instructions identified by `R_ARM_V4BX' relocations
   5111 with a branch to the following veneer:
   5112 
   5113      TST rM, #1
   5114      MOVEQ PC, rM
   5115      BX Rn
   5116 
   5117    This allows generation of libraries/applications that work on ARMv4
   5118 cores and are still interworking safe.  Note that the above veneer
   5119 clobbers the condition flags, so may cause incorrect progrm behavior in
   5120 rare cases.
   5121 
   5122    The `--use-blx' switch enables the linker to use ARM/Thumb BLX
   5123 instructions (available on ARMv5t and above) in various situations.
   5124 Currently it is used to perform calls via the PLT from Thumb code using
   5125 BLX rather than using BX and a mode-switching stub before each PLT
   5126 entry. This should lead to such calls executing slightly faster.
   5127 
   5128    This option is enabled implicitly for SymbianOS, so there is no need
   5129 to specify it if you are using that target.
   5130 
   5131    The `--vfp11-denorm-fix' switch enables a link-time workaround for a
   5132 bug in certain VFP11 coprocessor hardware, which sometimes allows
   5133 instructions with denorm operands (which must be handled by support
   5134 code) to have those operands overwritten by subsequent instructions
   5135 before the support code can read the intended values.
   5136 
   5137    The bug may be avoided in scalar mode if you allow at least one
   5138 intervening instruction between a VFP11 instruction which uses a
   5139 register and another instruction which writes to the same register, or
   5140 at least two intervening instructions if vector mode is in use. The bug
   5141 only affects full-compliance floating-point mode: you do not need this
   5142 workaround if you are using "runfast" mode. Please contact ARM for
   5143 further details.
   5144 
   5145    If you know you are using buggy VFP11 hardware, you can enable this
   5146 workaround by specifying the linker option `--vfp-denorm-fix=scalar' if
   5147 you are using the VFP11 scalar mode only, or `--vfp-denorm-fix=vector'
   5148 if you are using vector mode (the latter also works for scalar code).
   5149 The default is `--vfp-denorm-fix=none'.
   5150 
   5151    If the workaround is enabled, instructions are scanned for
   5152 potentially-troublesome sequences, and a veneer is created for each
   5153 such sequence which may trigger the erratum. The veneer consists of the
   5154 first instruction of the sequence and a branch back to the subsequent
   5155 instruction. The original instruction is then replaced with a branch to
   5156 the veneer. The extra cycles required to call and return from the veneer
   5157 are sufficient to avoid the erratum in both the scalar and vector cases.
   5158 
   5159    The `--no-enum-size-warning' switch prevents the linker from warning
   5160 when linking object files that specify incompatible EABI enumeration
   5161 size attributes.  For example, with this switch enabled, linking of an
   5162 object file using 32-bit enumeration values with another using
   5163 enumeration values fitted into the smallest possible space will not be
   5164 diagnosed.
   5165 
   5166    The `--no-wchar-size-warning' switch prevents the linker from
   5167 warning when linking object files that specify incompatible EABI
   5168 `wchar_t' size attributes.  For example, with this switch enabled,
   5169 linking of an object file using 32-bit `wchar_t' values with another
   5170 using 16-bit `wchar_t' values will not be diagnosed.
   5171 
   5172    The `--pic-veneer' switch makes the linker use PIC sequences for
   5173 ARM/Thumb interworking veneers, even if the rest of the binary is not
   5174 PIC.  This avoids problems on uClinux targets where `--emit-relocs' is
   5175 used to generate relocatable binaries.
   5176 
   5177    The linker will automatically generate and insert small sequences of
   5178 code into a linked ARM ELF executable whenever an attempt is made to
   5179 perform a function call to a symbol that is too far away.  The
   5180 placement of these sequences of instructions - called stubs - is
   5181 controlled by the command line option `--stub-group-size=N'.  The
   5182 placement is important because a poor choice can create a need for
   5183 duplicate stubs, increasing the code sizw.  The linker will try to
   5184 group stubs together in order to reduce interruptions to the flow of
   5185 code, but it needs guidance as to how big these groups should be and
   5186 where they should be placed.
   5187 
   5188    The value of `N', the parameter to the `--stub-group-size=' option
   5189 controls where the stub groups are placed.  If it is negative then all
   5190 stubs are placed after the first branch that needs them.  If it is
   5191 positive then the stubs can be placed either before or after the
   5192 branches that need them.  If the value of `N' is 1 (either +1 or -1)
   5193 then the linker will choose exactly where to place groups of stubs,
   5194 using its built in heuristics.  A value of `N' greater than 1 (or
   5195 smaller than -1) tells the linker that a single group of stubs can
   5196 service at most `N' bytes from the input sections.
   5197 
   5198    The default, if `--stub-group-size=' is not specified, is `N = +1'.
   5199 
   5200    Farcalls stubs insertion is fully supported for the ARM-EABI target
   5201 only, because it relies on object files properties not present
   5202 otherwise.
   5203 
   5204 
   5205 File: ld.info,  Node: HPPA ELF32,  Next: M68K,  Prev: ARM,  Up: Machine Dependent
   5206 
   5207 4.5 `ld' and HPPA 32-bit ELF Support
   5208 ====================================
   5209 
   5210 When generating a shared library, `ld' will by default generate import
   5211 stubs suitable for use with a single sub-space application.  The
   5212 `--multi-subspace' switch causes `ld' to generate export stubs, and
   5213 different (larger) import stubs suitable for use with multiple
   5214 sub-spaces.
   5215 
   5216    Long branch stubs and import/export stubs are placed by `ld' in stub
   5217 sections located between groups of input sections.  `--stub-group-size'
   5218 specifies the maximum size of a group of input sections handled by one
   5219 stub section.  Since branch offsets are signed, a stub section may
   5220 serve two groups of input sections, one group before the stub section,
   5221 and one group after it.  However, when using conditional branches that
   5222 require stubs, it may be better (for branch prediction) that stub
   5223 sections only serve one group of input sections.  A negative value for
   5224 `N' chooses this scheme, ensuring that branches to stubs always use a
   5225 negative offset.  Two special values of `N' are recognized, `1' and
   5226 `-1'.  These both instruct `ld' to automatically size input section
   5227 groups for the branch types detected, with the same behaviour regarding
   5228 stub placement as other positive or negative values of `N' respectively.
   5229 
   5230    Note that `--stub-group-size' does not split input sections.  A
   5231 single input section larger than the group size specified will of course
   5232 create a larger group (of one section).  If input sections are too
   5233 large, it may not be possible for a branch to reach its stub.
   5234 
   5235 
   5236 File: ld.info,  Node: M68K,  Next: MMIX,  Prev: HPPA ELF32,  Up: Machine Dependent
   5237 
   5238 4.6 `ld' and the Motorola 68K family
   5239 ====================================
   5240 
   5241 The `--got=TYPE' option lets you choose the GOT generation scheme.  The
   5242 choices are `single', `negative', `multigot' and `target'.  When
   5243 `target' is selected the linker chooses the default GOT generation
   5244 scheme for the current target.  `single' tells the linker to generate a
   5245 single GOT with entries only at non-negative offsets.  `negative'
   5246 instructs the linker to generate a single GOT with entries at both
   5247 negative and positive offsets.  Not all environments support such GOTs.
   5248 `multigot' allows the linker to generate several GOTs in the output
   5249 file.  All GOT references from a single input object file access the
   5250 same GOT, but references from different input object files might access
   5251 different GOTs.  Not all environments support such GOTs.
   5252 
   5253 
   5254 File: ld.info,  Node: MMIX,  Next: MSP430,  Prev: M68K,  Up: Machine Dependent
   5255 
   5256 4.7 `ld' and MMIX
   5257 =================
   5258 
   5259 For MMIX, there is a choice of generating `ELF' object files or `mmo'
   5260 object files when linking.  The simulator `mmix' understands the `mmo'
   5261 format.  The binutils `objcopy' utility can translate between the two
   5262 formats.
   5263 
   5264    There is one special section, the `.MMIX.reg_contents' section.
   5265 Contents in this section is assumed to correspond to that of global
   5266 registers, and symbols referring to it are translated to special
   5267 symbols, equal to registers.  In a final link, the start address of the
   5268 `.MMIX.reg_contents' section corresponds to the first allocated global
   5269 register multiplied by 8.  Register `$255' is not included in this
   5270 section; it is always set to the program entry, which is at the symbol
   5271 `Main' for `mmo' files.
   5272 
   5273    Global symbols with the prefix `__.MMIX.start.', for example
   5274 `__.MMIX.start..text' and `__.MMIX.start..data' are special.  The
   5275 default linker script uses these to set the default start address of a
   5276 section.
   5277 
   5278    Initial and trailing multiples of zero-valued 32-bit words in a
   5279 section, are left out from an mmo file.
   5280 
   5281 
   5282 File: ld.info,  Node: MSP430,  Next: M68HC11/68HC12,  Prev: MMIX,  Up: Machine Dependent
   5283 
   5284 4.8 `ld' and MSP430
   5285 ===================
   5286 
   5287 For the MSP430 it is possible to select the MPU architecture.  The flag
   5288 `-m [mpu type]' will select an appropriate linker script for selected
   5289 MPU type.  (To get a list of known MPUs just pass `-m help' option to
   5290 the linker).
   5291 
   5292    The linker will recognize some extra sections which are MSP430
   5293 specific:
   5294 
   5295 ``.vectors''
   5296      Defines a portion of ROM where interrupt vectors located.
   5297 
   5298 ``.bootloader''
   5299      Defines the bootloader portion of the ROM (if applicable).  Any
   5300      code in this section will be uploaded to the MPU.
   5301 
   5302 ``.infomem''
   5303      Defines an information memory section (if applicable).  Any code in
   5304      this section will be uploaded to the MPU.
   5305 
   5306 ``.infomemnobits''
   5307      This is the same as the `.infomem' section except that any code in
   5308      this section will not be uploaded to the MPU.
   5309 
   5310 ``.noinit''
   5311      Denotes a portion of RAM located above `.bss' section.
   5312 
   5313      The last two sections are used by gcc.
   5314 
   5315 
   5316 File: ld.info,  Node: PowerPC ELF32,  Next: PowerPC64 ELF64,  Prev: M68HC11/68HC12,  Up: Machine Dependent
   5317 
   5318 4.9 `ld' and PowerPC 32-bit ELF Support
   5319 =======================================
   5320 
   5321 Branches on PowerPC processors are limited to a signed 26-bit
   5322 displacement, which may result in `ld' giving `relocation truncated to
   5323 fit' errors with very large programs.  `--relax' enables the generation
   5324 of trampolines that can access the entire 32-bit address space.  These
   5325 trampolines are inserted at section boundaries, so may not themselves
   5326 be reachable if an input section exceeds 33M in size.  You may combine
   5327 `-r' and `--relax' to add trampolines in a partial link.  In that case
   5328 both branches to undefined symbols and inter-section branches are also
   5329 considered potentially out of range, and trampolines inserted.
   5330 
   5331 `--bss-plt'
   5332      Current PowerPC GCC accepts a `-msecure-plt' option that generates
   5333      code capable of using a newer PLT and GOT layout that has the
   5334      security advantage of no executable section ever needing to be
   5335      writable and no writable section ever being executable.  PowerPC
   5336      `ld' will generate this layout, including stubs to access the PLT,
   5337      if all input files (including startup and static libraries) were
   5338      compiled with `-msecure-plt'.  `--bss-plt' forces the old BSS PLT
   5339      (and GOT layout) which can give slightly better performance.
   5340 
   5341 `--secure-plt'
   5342      `ld' will use the new PLT and GOT layout if it is linking new
   5343      `-fpic' or `-fPIC' code, but does not do so automatically when
   5344      linking non-PIC code.  This option requests the new PLT and GOT
   5345      layout.  A warning will be given if some object file requires the
   5346      old style BSS PLT.
   5347 
   5348 `--sdata-got'
   5349      The new secure PLT and GOT are placed differently relative to other
   5350      sections compared to older BSS PLT and GOT placement.  The
   5351      location of `.plt' must change because the new secure PLT is an
   5352      initialized section while the old PLT is uninitialized.  The
   5353      reason for the `.got' change is more subtle:  The new placement
   5354      allows `.got' to be read-only in applications linked with `-z
   5355      relro -z now'.  However, this placement means that `.sdata' cannot
   5356      always be used in shared libraries, because the PowerPC ABI
   5357      accesses `.sdata' in shared libraries from the GOT pointer.
   5358      `--sdata-got' forces the old GOT placement.  PowerPC GCC doesn't
   5359      use `.sdata' in shared libraries, so this option is really only
   5360      useful for other compilers that may do so.
   5361 
   5362 `--emit-stub-syms'
   5363      This option causes `ld' to label linker stubs with a local symbol
   5364      that encodes the stub type and destination.
   5365 
   5366 `--no-tls-optimize'
   5367      PowerPC `ld' normally performs some optimization of code sequences
   5368      used to access Thread-Local Storage.  Use this option to disable
   5369      the optimization.
   5370 
   5371 
   5372 File: ld.info,  Node: PowerPC64 ELF64,  Next: SPU ELF,  Prev: PowerPC ELF32,  Up: Machine Dependent
   5373 
   5374 4.10 `ld' and PowerPC64 64-bit ELF Support
   5375 ==========================================
   5376 
   5377 `--stub-group-size'
   5378      Long branch stubs, PLT call stubs  and TOC adjusting stubs are
   5379      placed by `ld' in stub sections located between groups of input
   5380      sections.  `--stub-group-size' specifies the maximum size of a
   5381      group of input sections handled by one stub section.  Since branch
   5382      offsets are signed, a stub section may serve two groups of input
   5383      sections, one group before the stub section, and one group after
   5384      it.  However, when using conditional branches that require stubs,
   5385      it may be better (for branch prediction) that stub sections only
   5386      serve one group of input sections.  A negative value for `N'
   5387      chooses this scheme, ensuring that branches to stubs always use a
   5388      negative offset.  Two special values of `N' are recognized, `1'
   5389      and `-1'.  These both instruct `ld' to automatically size input
   5390      section groups for the branch types detected, with the same
   5391      behaviour regarding stub placement as other positive or negative
   5392      values of `N' respectively.
   5393 
   5394      Note that `--stub-group-size' does not split input sections.  A
   5395      single input section larger than the group size specified will of
   5396      course create a larger group (of one section).  If input sections
   5397      are too large, it may not be possible for a branch to reach its
   5398      stub.
   5399 
   5400 `--emit-stub-syms'
   5401      This option causes `ld' to label linker stubs with a local symbol
   5402      that encodes the stub type and destination.
   5403 
   5404 `--dotsyms, --no-dotsyms'
   5405      These two options control how `ld' interprets version patterns in
   5406      a version script.  Older PowerPC64 compilers emitted both a
   5407      function descriptor symbol with the same name as the function, and
   5408      a code entry symbol with the name prefixed by a dot (`.').  To
   5409      properly version a function `foo', the version script thus needs
   5410      to control both `foo' and `.foo'.  The option `--dotsyms', on by
   5411      default, automatically adds the required dot-prefixed patterns.
   5412      Use `--no-dotsyms' to disable this feature.
   5413 
   5414 `--no-tls-optimize'
   5415      PowerPC64 `ld' normally performs some optimization of code
   5416      sequences used to access Thread-Local Storage.  Use this option to
   5417      disable the optimization.
   5418 
   5419 `--no-opd-optimize'
   5420      PowerPC64 `ld' normally removes `.opd' section entries
   5421      corresponding to deleted link-once functions, or functions removed
   5422      by the action of `--gc-sections' or linker script `/DISCARD/'.
   5423      Use this option to disable `.opd' optimization.
   5424 
   5425 `--non-overlapping-opd'
   5426      Some PowerPC64 compilers have an option to generate compressed
   5427      `.opd' entries spaced 16 bytes apart, overlapping the third word,
   5428      the static chain pointer (unused in C) with the first word of the
   5429      next entry.  This option expands such entries to the full 24 bytes.
   5430 
   5431 `--no-toc-optimize'
   5432      PowerPC64 `ld' normally removes unused `.toc' section entries.
   5433      Such entries are detected by examining relocations that reference
   5434      the TOC in code sections.  A reloc in a deleted code section marks
   5435      a TOC word as unneeded, while a reloc in a kept code section marks
   5436      a TOC word as needed.  Since the TOC may reference itself, TOC
   5437      relocs are also examined.  TOC words marked as both needed and
   5438      unneeded will of course be kept.  TOC words without any referencing
   5439      reloc are assumed to be part of a multi-word entry, and are kept or
   5440      discarded as per the nearest marked preceding word.  This works
   5441      reliably for compiler generated code, but may be incorrect if
   5442      assembly code is used to insert TOC entries.  Use this option to
   5443      disable the optimization.
   5444 
   5445 `--no-multi-toc'
   5446      By default, PowerPC64 GCC generates code for a TOC model where TOC
   5447      entries are accessed with a 16-bit offset from r2.  This limits the
   5448      total TOC size to 64K.  PowerPC64 `ld' extends this limit by
   5449      grouping code sections such that each group uses less than 64K for
   5450      its TOC entries, then inserts r2 adjusting stubs between
   5451      inter-group calls.  `ld' does not split apart input sections, so
   5452      cannot help if a single input file has a `.toc' section that
   5453      exceeds 64K, most likely from linking multiple files with `ld -r'.
   5454      Use this option to turn off this feature.
   5455 
   5456 
   5457 File: ld.info,  Node: SPU ELF,  Next: TI COFF,  Prev: PowerPC64 ELF64,  Up: Machine Dependent
   5458 
   5459 4.11 `ld' and SPU ELF Support
   5460 =============================
   5461 
   5462 `--plugin'
   5463      This option marks an executable as a PIC plugin module.
   5464 
   5465 `--no-overlays'
   5466      Normally, `ld' recognizes calls to functions within overlay
   5467      regions, and redirects such calls to an overlay manager via a stub.
   5468      `ld' also provides a built-in overlay manager.  This option turns
   5469      off all this special overlay handling.
   5470 
   5471 `--emit-stub-syms'
   5472      This option causes `ld' to label overlay stubs with a local symbol
   5473      that encodes the stub type and destination.
   5474 
   5475 `--extra-overlay-stubs'
   5476      This option causes `ld' to add overlay call stubs on all function
   5477      calls out of overlay regions.  Normally stubs are not added on
   5478      calls to non-overlay regions.
   5479 
   5480 `--local-store=lo:hi'
   5481      `ld' usually checks that a final executable for SPU fits in the
   5482      address range 0 to 256k.  This option may be used to change the
   5483      range.  Disable the check entirely with `--local-store=0:0'.
   5484 
   5485 `--stack-analysis'
   5486      SPU local store space is limited.  Over-allocation of stack space
   5487      unnecessarily limits space available for code and data, while
   5488      under-allocation results in runtime failures.  If given this
   5489      option, `ld' will provide an estimate of maximum stack usage.
   5490      `ld' does this by examining symbols in code sections to determine
   5491      the extents of functions, and looking at function prologues for
   5492      stack adjusting instructions.  A call-graph is created by looking
   5493      for relocations on branch instructions.  The graph is then searched
   5494      for the maximum stack usage path.  Note that this analysis does not
   5495      find calls made via function pointers, and does not handle
   5496      recursion and other cycles in the call graph.  Stack usage may be
   5497      under-estimated if your code makes such calls.  Also, stack usage
   5498      for dynamic allocation, e.g. alloca, will not be detected.  If a
   5499      link map is requested, detailed information about each function's
   5500      stack usage and calls will be given.
   5501 
   5502 `--emit-stack-syms'
   5503      This option, if given along with `--stack-analysis' will result in
   5504      `ld' emitting stack sizing symbols for each function.  These take
   5505      the form `__stack_<function_name>' for global functions, and
   5506      `__stack_<number>_<function_name>' for static functions.
   5507      `<number>' is the section id in hex.  The value of such symbols is
   5508      the stack requirement for the corresponding function.  The symbol
   5509      size will be zero, type `STT_NOTYPE', binding `STB_LOCAL', and
   5510      section `SHN_ABS'.
   5511 
   5512 
   5513 File: ld.info,  Node: TI COFF,  Next: WIN32,  Prev: SPU ELF,  Up: Machine Dependent
   5514 
   5515 4.12 `ld''s Support for Various TI COFF Versions
   5516 ================================================
   5517 
   5518 The `--format' switch allows selection of one of the various TI COFF
   5519 versions.  The latest of this writing is 2; versions 0 and 1 are also
   5520 supported.  The TI COFF versions also vary in header byte-order format;
   5521 `ld' will read any version or byte order, but the output header format
   5522 depends on the default specified by the specific target.
   5523 
   5524 
   5525 File: ld.info,  Node: WIN32,  Next: Xtensa,  Prev: TI COFF,  Up: Machine Dependent
   5526 
   5527 4.13 `ld' and WIN32 (cygwin/mingw)
   5528 ==================================
   5529 
   5530 This section describes some of the win32 specific `ld' issues.  See
   5531 *note Command Line Options: Options. for detailed description of the
   5532 command line options mentioned here.
   5533 
   5534 _import libraries_
   5535      The standard Windows linker creates and uses so-called import
   5536      libraries, which contains information for linking to dll's.  They
   5537      are regular static archives and are handled as any other static
   5538      archive.  The cygwin and mingw ports of `ld' have specific support
   5539      for creating such libraries provided with the `--out-implib'
   5540      command line option.
   5541 
   5542 _exporting DLL symbols_
   5543      The cygwin/mingw `ld' has several ways to export symbols for dll's.
   5544 
   5545     _using auto-export functionality_
   5546           By default `ld' exports symbols with the auto-export
   5547           functionality, which is controlled by the following command
   5548           line options:
   5549 
   5550              * -export-all-symbols   [This is the default]
   5551 
   5552              * -exclude-symbols
   5553 
   5554              * -exclude-libs
   5555 
   5556              * -exclude-modules-for-implib
   5557 
   5558              * -version-script
   5559 
   5560           When auto-export is in operation, `ld' will export all the
   5561           non-local (global and common) symbols it finds in a DLL, with
   5562           the exception of a few symbols known to belong to the
   5563           system's runtime and libraries.  As it will often not be
   5564           desirable to export all of a DLL's symbols, which may include
   5565           private functions that are not part of any public interface,
   5566           the command-line options listed above may be used to filter
   5567           symbols out from the list for exporting.  The `--output-def'
   5568           option can be used in order to see the final list of exported
   5569           symbols with all exclusions taken into effect.
   5570 
   5571           If `--export-all-symbols' is not given explicitly on the
   5572           command line, then the default auto-export behavior will be
   5573           _disabled_ if either of the following are true:
   5574 
   5575              * A DEF file is used.
   5576 
   5577              * Any symbol in any object file was marked with the
   5578                __declspec(dllexport) attribute.
   5579 
   5580     _using a DEF file_
   5581           Another way of exporting symbols is using a DEF file.  A DEF
   5582           file is an ASCII file containing definitions of symbols which
   5583           should be exported when a dll is created.  Usually it is
   5584           named `<dll name>.def' and is added as any other object file
   5585           to the linker's command line.  The file's name must end in
   5586           `.def' or `.DEF'.
   5587 
   5588                gcc -o <output> <objectfiles> <dll name>.def
   5589 
   5590           Using a DEF file turns off the normal auto-export behavior,
   5591           unless the `--export-all-symbols' option is also used.
   5592 
   5593           Here is an example of a DEF file for a shared library called
   5594           `xyz.dll':
   5595 
   5596                LIBRARY "xyz.dll" BASE=0x20000000
   5597 
   5598                EXPORTS
   5599                foo
   5600                bar
   5601                _bar = bar
   5602                another_foo = abc.dll.afoo
   5603                var1 DATA
   5604                doo = foo == foo2
   5605                eoo DATA == var1
   5606 
   5607           This example defines a DLL with a non-default base address
   5608           and seven symbols in the export table. The third exported
   5609           symbol `_bar' is an alias for the second. The fourth symbol,
   5610           `another_foo' is resolved by "forwarding" to another module
   5611           and treating it as an alias for `afoo' exported from the DLL
   5612           `abc.dll'. The final symbol `var1' is declared to be a data
   5613           object. The `doo' symbol in export library is an alias of
   5614           `foo', which gets the string name in export table `foo2'. The
   5615           `eoo' symbol is an data export symbol, which gets in export
   5616           table the name `var1'.
   5617 
   5618           The optional `LIBRARY <name>' command indicates the _internal_
   5619           name of the output DLL. If `<name>' does not include a suffix,
   5620           the default library suffix, `.DLL' is appended.
   5621 
   5622           When the .DEF file is used to build an application, rather
   5623           than a library, the `NAME <name>' command should be used
   5624           instead of `LIBRARY'. If `<name>' does not include a suffix,
   5625           the default executable suffix, `.EXE' is appended.
   5626 
   5627           With either `LIBRARY <name>' or `NAME <name>' the optional
   5628           specification `BASE = <number>' may be used to specify a
   5629           non-default base address for the image.
   5630 
   5631           If neither `LIBRARY <name>' nor  `NAME <name>' is specified,
   5632           or they specify an empty string, the internal name is the
   5633           same as the filename specified on the command line.
   5634 
   5635           The complete specification of an export symbol is:
   5636 
   5637                EXPORTS
   5638                  ( (  ( <name1> [ = <name2> ] )
   5639                     | ( <name1> = <module-name> . <external-name>))
   5640                  [ @ <integer> ] [NONAME] [DATA] [CONSTANT] [PRIVATE] [== <name3>] ) *
   5641 
   5642           Declares `<name1>' as an exported symbol from the DLL, or
   5643           declares `<name1>' as an exported alias for `<name2>'; or
   5644           declares `<name1>' as a "forward" alias for the symbol
   5645           `<external-name>' in the DLL `<module-name>'.  Optionally,
   5646           the symbol may be exported by the specified ordinal
   5647           `<integer>' alias. The optional `<name3>' is the to be used
   5648           string in import/export table for the symbol.
   5649 
   5650           The optional keywords that follow the declaration indicate:
   5651 
   5652           `NONAME': Do not put the symbol name in the DLL's export
   5653           table.  It will still be exported by its ordinal alias
   5654           (either the value specified by the .def specification or,
   5655           otherwise, the value assigned by the linker). The symbol
   5656           name, however, does remain visible in the import library (if
   5657           any), unless `PRIVATE' is also specified.
   5658 
   5659           `DATA': The symbol is a variable or object, rather than a
   5660           function.  The import lib will export only an indirect
   5661           reference to `foo' as the symbol `_imp__foo' (ie, `foo' must
   5662           be resolved as `*_imp__foo').
   5663 
   5664           `CONSTANT': Like `DATA', but put the undecorated `foo' as
   5665           well as `_imp__foo' into the import library. Both refer to the
   5666           read-only import address table's pointer to the variable, not
   5667           to the variable itself. This can be dangerous. If the user
   5668           code fails to add the `dllimport' attribute and also fails to
   5669           explicitly add the extra indirection that the use of the
   5670           attribute enforces, the application will behave unexpectedly.
   5671 
   5672           `PRIVATE': Put the symbol in the DLL's export table, but do
   5673           not put it into the static import library used to resolve
   5674           imports at link time. The symbol can still be imported using
   5675           the `LoadLibrary/GetProcAddress' API at runtime or by by
   5676           using the GNU ld extension of linking directly to the DLL
   5677           without an import library.
   5678 
   5679           See ld/deffilep.y in the binutils sources for the full
   5680           specification of other DEF file statements
   5681 
   5682           While linking a shared dll, `ld' is able to create a DEF file
   5683           with the `--output-def <file>' command line option.
   5684 
   5685     _Using decorations_
   5686           Another way of marking symbols for export is to modify the
   5687           source code itself, so that when building the DLL each symbol
   5688           to be exported is declared as:
   5689 
   5690                __declspec(dllexport) int a_variable
   5691                __declspec(dllexport) void a_function(int with_args)
   5692 
   5693           All such symbols will be exported from the DLL.  If, however,
   5694           any of the object files in the DLL contain symbols decorated
   5695           in this way, then the normal auto-export behavior is
   5696           disabled, unless the `--export-all-symbols' option is also
   5697           used.
   5698 
   5699           Note that object files that wish to access these symbols must
   5700           _not_ decorate them with dllexport.  Instead, they should use
   5701           dllimport, instead:
   5702 
   5703                __declspec(dllimport) int a_variable
   5704                __declspec(dllimport) void a_function(int with_args)
   5705 
   5706           This complicates the structure of library header files,
   5707           because when included by the library itself the header must
   5708           declare the variables and functions as dllexport, but when
   5709           included by client code the header must declare them as
   5710           dllimport.  There are a number of idioms that are typically
   5711           used to do this; often client code can omit the __declspec()
   5712           declaration completely.  See `--enable-auto-import' and
   5713           `automatic data imports' for more information.
   5714 
   5715 _automatic data imports_
   5716      The standard Windows dll format supports data imports from dlls
   5717      only by adding special decorations (dllimport/dllexport), which
   5718      let the compiler produce specific assembler instructions to deal
   5719      with this issue.  This increases the effort necessary to port
   5720      existing Un*x code to these platforms, especially for large c++
   5721      libraries and applications.  The auto-import feature, which was
   5722      initially provided by Paul Sokolovsky, allows one to omit the
   5723      decorations to achieve a behavior that conforms to that on
   5724      POSIX/Un*x platforms. This feature is enabled with the
   5725      `--enable-auto-import' command-line option, although it is enabled
   5726      by default on cygwin/mingw.  The `--enable-auto-import' option
   5727      itself now serves mainly to suppress any warnings that are
   5728      ordinarily emitted when linked objects trigger the feature's use.
   5729 
   5730      auto-import of variables does not always work flawlessly without
   5731      additional assistance.  Sometimes, you will see this message
   5732 
   5733      "variable '<var>' can't be auto-imported. Please read the
   5734      documentation for ld's `--enable-auto-import' for details."
   5735 
   5736      The `--enable-auto-import' documentation explains why this error
   5737      occurs, and several methods that can be used to overcome this
   5738      difficulty.  One of these methods is the _runtime pseudo-relocs_
   5739      feature, described below.
   5740 
   5741      For complex variables imported from DLLs (such as structs or
   5742      classes), object files typically contain a base address for the
   5743      variable and an offset (_addend_) within the variable-to specify a
   5744      particular field or public member, for instance.  Unfortunately,
   5745      the runtime loader used in win32 environments is incapable of
   5746      fixing these references at runtime without the additional
   5747      information supplied by dllimport/dllexport decorations.  The
   5748      standard auto-import feature described above is unable to resolve
   5749      these references.
   5750 
   5751      The `--enable-runtime-pseudo-relocs' switch allows these
   5752      references to be resolved without error, while leaving the task of
   5753      adjusting the references themselves (with their non-zero addends)
   5754      to specialized code provided by the runtime environment.  Recent
   5755      versions of the cygwin and mingw environments and compilers
   5756      provide this runtime support; older versions do not.  However, the
   5757      support is only necessary on the developer's platform; the
   5758      compiled result will run without error on an older system.
   5759 
   5760      `--enable-runtime-pseudo-relocs' is not the default; it must be
   5761      explicitly enabled as needed.
   5762 
   5763 _direct linking to a dll_
   5764      The cygwin/mingw ports of `ld' support the direct linking,
   5765      including data symbols, to a dll without the usage of any import
   5766      libraries.  This is much faster and uses much less memory than
   5767      does the traditional import library method, especially when
   5768      linking large libraries or applications.  When `ld' creates an
   5769      import lib, each function or variable exported from the dll is
   5770      stored in its own bfd, even though a single bfd could contain many
   5771      exports.  The overhead involved in storing, loading, and
   5772      processing so many bfd's is quite large, and explains the
   5773      tremendous time, memory, and storage needed to link against
   5774      particularly large or complex libraries when using import libs.
   5775 
   5776      Linking directly to a dll uses no extra command-line switches
   5777      other than `-L' and `-l', because `ld' already searches for a
   5778      number of names to match each library.  All that is needed from
   5779      the developer's perspective is an understanding of this search, in
   5780      order to force ld to select the dll instead of an import library.
   5781 
   5782      For instance, when ld is called with the argument `-lxxx' it will
   5783      attempt to find, in the first directory of its search path,
   5784 
   5785           libxxx.dll.a
   5786           xxx.dll.a
   5787           libxxx.a
   5788           xxx.lib
   5789           cygxxx.dll (*)
   5790           libxxx.dll
   5791           xxx.dll
   5792 
   5793      before moving on to the next directory in the search path.
   5794 
   5795      (*) Actually, this is not `cygxxx.dll' but in fact is
   5796      `<prefix>xxx.dll', where `<prefix>' is set by the `ld' option
   5797      `--dll-search-prefix=<prefix>'. In the case of cygwin, the
   5798      standard gcc spec file includes `--dll-search-prefix=cyg', so in
   5799      effect we actually search for `cygxxx.dll'.
   5800 
   5801      Other win32-based unix environments, such as mingw or pw32, may
   5802      use other `<prefix>'es, although at present only cygwin makes use
   5803      of this feature.  It was originally intended to help avoid name
   5804      conflicts among dll's built for the various win32/un*x
   5805      environments, so that (for example) two versions of a zlib dll
   5806      could coexist on the same machine.
   5807 
   5808      The generic cygwin/mingw path layout uses a `bin' directory for
   5809      applications and dll's and a `lib' directory for the import
   5810      libraries (using cygwin nomenclature):
   5811 
   5812           bin/
   5813           	cygxxx.dll
   5814           lib/
   5815           	libxxx.dll.a   (in case of dll's)
   5816           	libxxx.a       (in case of static archive)
   5817 
   5818      Linking directly to a dll without using the import library can be
   5819      done two ways:
   5820 
   5821      1. Use the dll directly by adding the `bin' path to the link line
   5822           gcc -Wl,-verbose  -o a.exe -L../bin/ -lxxx
   5823 
   5824      However, as the dll's often have version numbers appended to their
   5825      names (`cygncurses-5.dll') this will often fail, unless one
   5826      specifies `-L../bin -lncurses-5' to include the version.  Import
   5827      libs are generally not versioned, and do not have this difficulty.
   5828 
   5829      2. Create a symbolic link from the dll to a file in the `lib'
   5830      directory according to the above mentioned search pattern.  This
   5831      should be used to avoid unwanted changes in the tools needed for
   5832      making the app/dll.
   5833 
   5834           ln -s bin/cygxxx.dll lib/[cyg|lib|]xxx.dll[.a]
   5835 
   5836      Then you can link without any make environment changes.
   5837 
   5838           gcc -Wl,-verbose  -o a.exe -L../lib/ -lxxx
   5839 
   5840      This technique also avoids the version number problems, because
   5841      the following is perfectly legal
   5842 
   5843           bin/
   5844           	cygxxx-5.dll
   5845           lib/
   5846           	libxxx.dll.a -> ../bin/cygxxx-5.dll
   5847 
   5848      Linking directly to a dll without using an import lib will work
   5849      even when auto-import features are exercised, and even when
   5850      `--enable-runtime-pseudo-relocs' is used.
   5851 
   5852      Given the improvements in speed and memory usage, one might
   5853      justifiably wonder why import libraries are used at all.  There
   5854      are three reasons:
   5855 
   5856      1. Until recently, the link-directly-to-dll functionality did _not_
   5857      work with auto-imported data.
   5858 
   5859      2. Sometimes it is necessary to include pure static objects within
   5860      the import library (which otherwise contains only bfd's for
   5861      indirection symbols that point to the exports of a dll).  Again,
   5862      the import lib for the cygwin kernel makes use of this ability,
   5863      and it is not possible to do this without an import lib.
   5864 
   5865      3. Symbol aliases can only be resolved using an import lib.  This
   5866      is critical when linking against OS-supplied dll's (eg, the win32
   5867      API) in which symbols are usually exported as undecorated aliases
   5868      of their stdcall-decorated assembly names.
   5869 
   5870      So, import libs are not going away.  But the ability to replace
   5871      true import libs with a simple symbolic link to (or a copy of) a
   5872      dll, in many cases, is a useful addition to the suite of tools
   5873      binutils makes available to the win32 developer.  Given the
   5874      massive improvements in memory requirements during linking, storage
   5875      requirements, and linking speed, we expect that many developers
   5876      will soon begin to use this feature whenever possible.
   5877 
   5878 _symbol aliasing_
   5879 
   5880     _adding additional names_
   5881           Sometimes, it is useful to export symbols with additional
   5882           names.  A symbol `foo' will be exported as `foo', but it can
   5883           also be exported as `_foo' by using special directives in the
   5884           DEF file when creating the dll.  This will affect also the
   5885           optional created import library.  Consider the following DEF
   5886           file:
   5887 
   5888                LIBRARY "xyz.dll" BASE=0x61000000
   5889 
   5890                EXPORTS
   5891                foo
   5892                _foo = foo
   5893 
   5894           The line `_foo = foo' maps the symbol `foo' to `_foo'.
   5895 
   5896           Another method for creating a symbol alias is to create it in
   5897           the source code using the "weak" attribute:
   5898 
   5899                void foo () { /* Do something.  */; }
   5900                void _foo () __attribute__ ((weak, alias ("foo")));
   5901 
   5902           See the gcc manual for more information about attributes and
   5903           weak symbols.
   5904 
   5905     _renaming symbols_
   5906           Sometimes it is useful to rename exports.  For instance, the
   5907           cygwin kernel does this regularly.  A symbol `_foo' can be
   5908           exported as `foo' but not as `_foo' by using special
   5909           directives in the DEF file. (This will also affect the import
   5910           library, if it is created).  In the following example:
   5911 
   5912                LIBRARY "xyz.dll" BASE=0x61000000
   5913 
   5914                EXPORTS
   5915                _foo = foo
   5916 
   5917           The line `_foo = foo' maps the exported symbol `foo' to
   5918           `_foo'.
   5919 
   5920      Note: using a DEF file disables the default auto-export behavior,
   5921      unless the `--export-all-symbols' command line option is used.
   5922      If, however, you are trying to rename symbols, then you should list
   5923      _all_ desired exports in the DEF file, including the symbols that
   5924      are not being renamed, and do _not_ use the `--export-all-symbols'
   5925      option.  If you list only the renamed symbols in the DEF file, and
   5926      use `--export-all-symbols' to handle the other symbols, then the
   5927      both the new names _and_ the original names for the renamed
   5928      symbols will be exported.  In effect, you'd be aliasing those
   5929      symbols, not renaming them, which is probably not what you wanted.
   5930 
   5931 _weak externals_
   5932      The Windows object format, PE, specifies a form of weak symbols
   5933      called weak externals.  When a weak symbol is linked and the
   5934      symbol is not defined, the weak symbol becomes an alias for some
   5935      other symbol.  There are three variants of weak externals:
   5936         * Definition is searched for in objects and libraries,
   5937           historically called lazy externals.
   5938 
   5939         * Definition is searched for only in other objects, not in
   5940           libraries.  This form is not presently implemented.
   5941 
   5942         * No search; the symbol is an alias.  This form is not presently
   5943           implemented.
   5944      As a GNU extension, weak symbols that do not specify an alternate
   5945      symbol are supported.  If the symbol is undefined when linking,
   5946      the symbol uses a default value.
   5947 
   5948 _aligned common symbols_
   5949      As a GNU extension to the PE file format, it is possible to
   5950      specify the desired alignment for a common symbol.  This
   5951      information is conveyed from the assembler or compiler to the
   5952      linker by means of GNU-specific commands carried in the object
   5953      file's `.drectve' section, which are recognized by `ld' and
   5954      respected when laying out the common symbols.  Native tools will
   5955      be able to process object files employing this GNU extension, but
   5956      will fail to respect the alignment instructions, and may issue
   5957      noisy warnings about unknown linker directives.
   5958 
   5959 
   5960 File: ld.info,  Node: Xtensa,  Prev: WIN32,  Up: Machine Dependent
   5961 
   5962 4.14 `ld' and Xtensa Processors
   5963 ===============================
   5964 
   5965 The default `ld' behavior for Xtensa processors is to interpret
   5966 `SECTIONS' commands so that lists of explicitly named sections in a
   5967 specification with a wildcard file will be interleaved when necessary to
   5968 keep literal pools within the range of PC-relative load offsets.  For
   5969 example, with the command:
   5970 
   5971      SECTIONS
   5972      {
   5973        .text : {
   5974          *(.literal .text)
   5975        }
   5976      }
   5977 
   5978 `ld' may interleave some of the `.literal' and `.text' sections from
   5979 different object files to ensure that the literal pools are within the
   5980 range of PC-relative load offsets.  A valid interleaving might place
   5981 the `.literal' sections from an initial group of files followed by the
   5982 `.text' sections of that group of files.  Then, the `.literal' sections
   5983 from the rest of the files and the `.text' sections from the rest of
   5984 the files would follow.
   5985 
   5986    Relaxation is enabled by default for the Xtensa version of `ld' and
   5987 provides two important link-time optimizations.  The first optimization
   5988 is to combine identical literal values to reduce code size.  A redundant
   5989 literal will be removed and all the `L32R' instructions that use it
   5990 will be changed to reference an identical literal, as long as the
   5991 location of the replacement literal is within the offset range of all
   5992 the `L32R' instructions.  The second optimization is to remove
   5993 unnecessary overhead from assembler-generated "longcall" sequences of
   5994 `L32R'/`CALLXN' when the target functions are within range of direct
   5995 `CALLN' instructions.
   5996 
   5997    For each of these cases where an indirect call sequence can be
   5998 optimized to a direct call, the linker will change the `CALLXN'
   5999 instruction to a `CALLN' instruction, remove the `L32R' instruction,
   6000 and remove the literal referenced by the `L32R' instruction if it is
   6001 not used for anything else.  Removing the `L32R' instruction always
   6002 reduces code size but can potentially hurt performance by changing the
   6003 alignment of subsequent branch targets.  By default, the linker will
   6004 always preserve alignments, either by switching some instructions
   6005 between 24-bit encodings and the equivalent density instructions or by
   6006 inserting a no-op in place of the `L32R' instruction that was removed.
   6007 If code size is more important than performance, the `--size-opt'
   6008 option can be used to prevent the linker from widening density
   6009 instructions or inserting no-ops, except in a few cases where no-ops
   6010 are required for correctness.
   6011 
   6012    The following Xtensa-specific command-line options can be used to
   6013 control the linker:
   6014 
   6015 `--size-opt'
   6016      When optimizing indirect calls to direct calls, optimize for code
   6017      size more than performance.  With this option, the linker will not
   6018      insert no-ops or widen density instructions to preserve branch
   6019      target alignment.  There may still be some cases where no-ops are
   6020      required to preserve the correctness of the code.
   6021 
   6022 
   6023 File: ld.info,  Node: BFD,  Next: Reporting Bugs,  Prev: Machine Dependent,  Up: Top
   6024 
   6025 5 BFD
   6026 *****
   6027 
   6028 The linker accesses object and archive files using the BFD libraries.
   6029 These libraries allow the linker to use the same routines to operate on
   6030 object files whatever the object file format.  A different object file
   6031 format can be supported simply by creating a new BFD back end and adding
   6032 it to the library.  To conserve runtime memory, however, the linker and
   6033 associated tools are usually configured to support only a subset of the
   6034 object file formats available.  You can use `objdump -i' (*note
   6035 objdump: (binutils.info)objdump.) to list all the formats available for
   6036 your configuration.
   6037 
   6038    As with most implementations, BFD is a compromise between several
   6039 conflicting requirements. The major factor influencing BFD design was
   6040 efficiency: any time used converting between formats is time which
   6041 would not have been spent had BFD not been involved. This is partly
   6042 offset by abstraction payback; since BFD simplifies applications and
   6043 back ends, more time and care may be spent optimizing algorithms for a
   6044 greater speed.
   6045 
   6046    One minor artifact of the BFD solution which you should bear in mind
   6047 is the potential for information loss.  There are two places where
   6048 useful information can be lost using the BFD mechanism: during
   6049 conversion and during output. *Note BFD information loss::.
   6050 
   6051 * Menu:
   6052 
   6053 * BFD outline::                 How it works: an outline of BFD
   6054 
   6055 
   6056 File: ld.info,  Node: BFD outline,  Up: BFD
   6057 
   6058 5.1 How It Works: An Outline of BFD
   6059 ===================================
   6060 
   6061 When an object file is opened, BFD subroutines automatically determine
   6062 the format of the input object file.  They then build a descriptor in
   6063 memory with pointers to routines that will be used to access elements of
   6064 the object file's data structures.
   6065 
   6066    As different information from the object files is required, BFD
   6067 reads from different sections of the file and processes them.  For
   6068 example, a very common operation for the linker is processing symbol
   6069 tables.  Each BFD back end provides a routine for converting between
   6070 the object file's representation of symbols and an internal canonical
   6071 format. When the linker asks for the symbol table of an object file, it
   6072 calls through a memory pointer to the routine from the relevant BFD
   6073 back end which reads and converts the table into a canonical form.  The
   6074 linker then operates upon the canonical form. When the link is finished
   6075 and the linker writes the output file's symbol table, another BFD back
   6076 end routine is called to take the newly created symbol table and
   6077 convert it into the chosen output format.
   6078 
   6079 * Menu:
   6080 
   6081 * BFD information loss::	Information Loss
   6082 * Canonical format::		The BFD	canonical object-file format
   6083 
   6084 
   6085 File: ld.info,  Node: BFD information loss,  Next: Canonical format,  Up: BFD outline
   6086 
   6087 5.1.1 Information Loss
   6088 ----------------------
   6089 
   6090 _Information can be lost during output._ The output formats supported
   6091 by BFD do not provide identical facilities, and information which can
   6092 be described in one form has nowhere to go in another format. One
   6093 example of this is alignment information in `b.out'. There is nowhere
   6094 in an `a.out' format file to store alignment information on the
   6095 contained data, so when a file is linked from `b.out' and an `a.out'
   6096 image is produced, alignment information will not propagate to the
   6097 output file. (The linker will still use the alignment information
   6098 internally, so the link is performed correctly).
   6099 
   6100    Another example is COFF section names. COFF files may contain an
   6101 unlimited number of sections, each one with a textual section name. If
   6102 the target of the link is a format which does not have many sections
   6103 (e.g., `a.out') or has sections without names (e.g., the Oasys format),
   6104 the link cannot be done simply. You can circumvent this problem by
   6105 describing the desired input-to-output section mapping with the linker
   6106 command language.
   6107 
   6108    _Information can be lost during canonicalization._ The BFD internal
   6109 canonical form of the external formats is not exhaustive; there are
   6110 structures in input formats for which there is no direct representation
   6111 internally.  This means that the BFD back ends cannot maintain all
   6112 possible data richness through the transformation between external to
   6113 internal and back to external formats.
   6114 
   6115    This limitation is only a problem when an application reads one
   6116 format and writes another.  Each BFD back end is responsible for
   6117 maintaining as much data as possible, and the internal BFD canonical
   6118 form has structures which are opaque to the BFD core, and exported only
   6119 to the back ends. When a file is read in one format, the canonical form
   6120 is generated for BFD and the application. At the same time, the back
   6121 end saves away any information which may otherwise be lost. If the data
   6122 is then written back in the same format, the back end routine will be
   6123 able to use the canonical form provided by the BFD core as well as the
   6124 information it prepared earlier.  Since there is a great deal of
   6125 commonality between back ends, there is no information lost when
   6126 linking or copying big endian COFF to little endian COFF, or `a.out' to
   6127 `b.out'.  When a mixture of formats is linked, the information is only
   6128 lost from the files whose format differs from the destination.
   6129 
   6130 
   6131 File: ld.info,  Node: Canonical format,  Prev: BFD information loss,  Up: BFD outline
   6132 
   6133 5.1.2 The BFD canonical object-file format
   6134 ------------------------------------------
   6135 
   6136 The greatest potential for loss of information occurs when there is the
   6137 least overlap between the information provided by the source format,
   6138 that stored by the canonical format, and that needed by the destination
   6139 format. A brief description of the canonical form may help you
   6140 understand which kinds of data you can count on preserving across
   6141 conversions.  
   6142 
   6143 _files_
   6144      Information stored on a per-file basis includes target machine
   6145      architecture, particular implementation format type, a demand
   6146      pageable bit, and a write protected bit.  Information like Unix
   6147      magic numbers is not stored here--only the magic numbers' meaning,
   6148      so a `ZMAGIC' file would have both the demand pageable bit and the
   6149      write protected text bit set.  The byte order of the target is
   6150      stored on a per-file basis, so that big- and little-endian object
   6151      files may be used with one another.
   6152 
   6153 _sections_
   6154      Each section in the input file contains the name of the section,
   6155      the section's original address in the object file, size and
   6156      alignment information, various flags, and pointers into other BFD
   6157      data structures.
   6158 
   6159 _symbols_
   6160      Each symbol contains a pointer to the information for the object
   6161      file which originally defined it, its name, its value, and various
   6162      flag bits.  When a BFD back end reads in a symbol table, it
   6163      relocates all symbols to make them relative to the base of the
   6164      section where they were defined.  Doing this ensures that each
   6165      symbol points to its containing section.  Each symbol also has a
   6166      varying amount of hidden private data for the BFD back end.  Since
   6167      the symbol points to the original file, the private data format
   6168      for that symbol is accessible.  `ld' can operate on a collection
   6169      of symbols of wildly different formats without problems.
   6170 
   6171      Normal global and simple local symbols are maintained on output,
   6172      so an output file (no matter its format) will retain symbols
   6173      pointing to functions and to global, static, and common variables.
   6174      Some symbol information is not worth retaining; in `a.out', type
   6175      information is stored in the symbol table as long symbol names.
   6176      This information would be useless to most COFF debuggers; the
   6177      linker has command line switches to allow users to throw it away.
   6178 
   6179      There is one word of type information within the symbol, so if the
   6180      format supports symbol type information within symbols (for
   6181      example, COFF, IEEE, Oasys) and the type is simple enough to fit
   6182      within one word (nearly everything but aggregates), the
   6183      information will be preserved.
   6184 
   6185 _relocation level_
   6186      Each canonical BFD relocation record contains a pointer to the
   6187      symbol to relocate to, the offset of the data to relocate, the
   6188      section the data is in, and a pointer to a relocation type
   6189      descriptor. Relocation is performed by passing messages through
   6190      the relocation type descriptor and the symbol pointer. Therefore,
   6191      relocations can be performed on output data using a relocation
   6192      method that is only available in one of the input formats. For
   6193      instance, Oasys provides a byte relocation format.  A relocation
   6194      record requesting this relocation type would point indirectly to a
   6195      routine to perform this, so the relocation may be performed on a
   6196      byte being written to a 68k COFF file, even though 68k COFF has no
   6197      such relocation type.
   6198 
   6199 _line numbers_
   6200      Object formats can contain, for debugging purposes, some form of
   6201      mapping between symbols, source line numbers, and addresses in the
   6202      output file.  These addresses have to be relocated along with the
   6203      symbol information.  Each symbol with an associated list of line
   6204      number records points to the first record of the list.  The head
   6205      of a line number list consists of a pointer to the symbol, which
   6206      allows finding out the address of the function whose line number
   6207      is being described. The rest of the list is made up of pairs:
   6208      offsets into the section and line numbers. Any format which can
   6209      simply derive this information can pass it successfully between
   6210      formats (COFF, IEEE and Oasys).
   6211 
   6212 
   6213 File: ld.info,  Node: Reporting Bugs,  Next: MRI,  Prev: BFD,  Up: Top
   6214 
   6215 6 Reporting Bugs
   6216 ****************
   6217 
   6218 Your bug reports play an essential role in making `ld' reliable.
   6219 
   6220    Reporting a bug may help you by bringing a solution to your problem,
   6221 or it may not.  But in any case the principal function of a bug report
   6222 is to help the entire community by making the next version of `ld' work
   6223 better.  Bug reports are your contribution to the maintenance of `ld'.
   6224 
   6225    In order for a bug report to serve its purpose, you must include the
   6226 information that enables us to fix the bug.
   6227 
   6228 * Menu:
   6229 
   6230 * Bug Criteria::                Have you found a bug?
   6231 * Bug Reporting::               How to report bugs
   6232 
   6233 
   6234 File: ld.info,  Node: Bug Criteria,  Next: Bug Reporting,  Up: Reporting Bugs
   6235 
   6236 6.1 Have You Found a Bug?
   6237 =========================
   6238 
   6239 If you are not sure whether you have found a bug, here are some
   6240 guidelines:
   6241 
   6242    * If the linker gets a fatal signal, for any input whatever, that is
   6243      a `ld' bug.  Reliable linkers never crash.
   6244 
   6245    * If `ld' produces an error message for valid input, that is a bug.
   6246 
   6247    * If `ld' does not produce an error message for invalid input, that
   6248      may be a bug.  In the general case, the linker can not verify that
   6249      object files are correct.
   6250 
   6251    * If you are an experienced user of linkers, your suggestions for
   6252      improvement of `ld' are welcome in any case.
   6253 
   6254 
   6255 File: ld.info,  Node: Bug Reporting,  Prev: Bug Criteria,  Up: Reporting Bugs
   6256 
   6257 6.2 How to Report Bugs
   6258 ======================
   6259 
   6260 A number of companies and individuals offer support for GNU products.
   6261 If you obtained `ld' from a support organization, we recommend you
   6262 contact that organization first.
   6263 
   6264    You can find contact information for many support companies and
   6265 individuals in the file `etc/SERVICE' in the GNU Emacs distribution.
   6266 
   6267    Otherwise, send bug reports for `ld' to
   6268 `http://www.sourceware.org/bugzilla/'.
   6269 
   6270    The fundamental principle of reporting bugs usefully is this:
   6271 *report all the facts*.  If you are not sure whether to state a fact or
   6272 leave it out, state it!
   6273 
   6274    Often people omit facts because they think they know what causes the
   6275 problem and assume that some details do not matter.  Thus, you might
   6276 assume that the name of a symbol you use in an example does not matter.
   6277 Well, probably it does not, but one cannot be sure.  Perhaps the bug is
   6278 a stray memory reference which happens to fetch from the location where
   6279 that name is stored in memory; perhaps, if the name were different, the
   6280 contents of that location would fool the linker into doing the right
   6281 thing despite the bug.  Play it safe and give a specific, complete
   6282 example.  That is the easiest thing for you to do, and the most helpful.
   6283 
   6284    Keep in mind that the purpose of a bug report is to enable us to fix
   6285 the bug if it is new to us.  Therefore, always write your bug reports
   6286 on the assumption that the bug has not been reported previously.
   6287 
   6288    Sometimes people give a few sketchy facts and ask, "Does this ring a
   6289 bell?"  This cannot help us fix a bug, so it is basically useless.  We
   6290 respond by asking for enough details to enable us to investigate.  You
   6291 might as well expedite matters by sending them to begin with.
   6292 
   6293    To enable us to fix the bug, you should include all these things:
   6294 
   6295    * The version of `ld'.  `ld' announces it if you start it with the
   6296      `--version' argument.
   6297 
   6298      Without this, we will not know whether there is any point in
   6299      looking for the bug in the current version of `ld'.
   6300 
   6301    * Any patches you may have applied to the `ld' source, including any
   6302      patches made to the `BFD' library.
   6303 
   6304    * The type of machine you are using, and the operating system name
   6305      and version number.
   6306 
   6307    * What compiler (and its version) was used to compile `ld'--e.g.
   6308      "`gcc-2.7'".
   6309 
   6310    * The command arguments you gave the linker to link your example and
   6311      observe the bug.  To guarantee you will not omit something
   6312      important, list them all.  A copy of the Makefile (or the output
   6313      from make) is sufficient.
   6314 
   6315      If we were to try to guess the arguments, we would probably guess
   6316      wrong and then we might not encounter the bug.
   6317 
   6318    * A complete input file, or set of input files, that will reproduce
   6319      the bug.  It is generally most helpful to send the actual object
   6320      files provided that they are reasonably small.  Say no more than
   6321      10K.  For bigger files you can either make them available by FTP
   6322      or HTTP or else state that you are willing to send the object
   6323      file(s) to whomever requests them.  (Note - your email will be
   6324      going to a mailing list, so we do not want to clog it up with
   6325      large attachments).  But small attachments are best.
   6326 
   6327      If the source files were assembled using `gas' or compiled using
   6328      `gcc', then it may be OK to send the source files rather than the
   6329      object files.  In this case, be sure to say exactly what version of
   6330      `gas' or `gcc' was used to produce the object files.  Also say how
   6331      `gas' or `gcc' were configured.
   6332 
   6333    * A description of what behavior you observe that you believe is
   6334      incorrect.  For example, "It gets a fatal signal."
   6335 
   6336      Of course, if the bug is that `ld' gets a fatal signal, then we
   6337      will certainly notice it.  But if the bug is incorrect output, we
   6338      might not notice unless it is glaringly wrong.  You might as well
   6339      not give us a chance to make a mistake.
   6340 
   6341      Even if the problem you experience is a fatal signal, you should
   6342      still say so explicitly.  Suppose something strange is going on,
   6343      such as, your copy of `ld' is out of sync, or you have encountered
   6344      a bug in the C library on your system.  (This has happened!)  Your
   6345      copy might crash and ours would not.  If you told us to expect a
   6346      crash, then when ours fails to crash, we would know that the bug
   6347      was not happening for us.  If you had not told us to expect a
   6348      crash, then we would not be able to draw any conclusion from our
   6349      observations.
   6350 
   6351    * If you wish to suggest changes to the `ld' source, send us context
   6352      diffs, as generated by `diff' with the `-u', `-c', or `-p' option.
   6353      Always send diffs from the old file to the new file.  If you even
   6354      discuss something in the `ld' source, refer to it by context, not
   6355      by line number.
   6356 
   6357      The line numbers in our development sources will not match those
   6358      in your sources.  Your line numbers would convey no useful
   6359      information to us.
   6360 
   6361    Here are some things that are not necessary:
   6362 
   6363    * A description of the envelope of the bug.
   6364 
   6365      Often people who encounter a bug spend a lot of time investigating
   6366      which changes to the input file will make the bug go away and which
   6367      changes will not affect it.
   6368 
   6369      This is often time consuming and not very useful, because the way
   6370      we will find the bug is by running a single example under the
   6371      debugger with breakpoints, not by pure deduction from a series of
   6372      examples.  We recommend that you save your time for something else.
   6373 
   6374      Of course, if you can find a simpler example to report _instead_
   6375      of the original one, that is a convenience for us.  Errors in the
   6376      output will be easier to spot, running under the debugger will take
   6377      less time, and so on.
   6378 
   6379      However, simplification is not vital; if you do not want to do
   6380      this, report the bug anyway and send us the entire test case you
   6381      used.
   6382 
   6383    * A patch for the bug.
   6384 
   6385      A patch for the bug does help us if it is a good one.  But do not
   6386      omit the necessary information, such as the test case, on the
   6387      assumption that a patch is all we need.  We might see problems
   6388      with your patch and decide to fix the problem another way, or we
   6389      might not understand it at all.
   6390 
   6391      Sometimes with a program as complicated as `ld' it is very hard to
   6392      construct an example that will make the program follow a certain
   6393      path through the code.  If you do not send us the example, we will
   6394      not be able to construct one, so we will not be able to verify
   6395      that the bug is fixed.
   6396 
   6397      And if we cannot understand what bug you are trying to fix, or why
   6398      your patch should be an improvement, we will not install it.  A
   6399      test case will help us to understand.
   6400 
   6401    * A guess about what the bug is or what it depends on.
   6402 
   6403      Such guesses are usually wrong.  Even we cannot guess right about
   6404      such things without first using the debugger to find the facts.
   6405 
   6406 
   6407 File: ld.info,  Node: MRI,  Next: GNU Free Documentation License,  Prev: Reporting Bugs,  Up: Top
   6408 
   6409 Appendix A MRI Compatible Script Files
   6410 **************************************
   6411 
   6412 To aid users making the transition to GNU `ld' from the MRI linker,
   6413 `ld' can use MRI compatible linker scripts as an alternative to the
   6414 more general-purpose linker scripting language described in *note
   6415 Scripts::.  MRI compatible linker scripts have a much simpler command
   6416 set than the scripting language otherwise used with `ld'.  GNU `ld'
   6417 supports the most commonly used MRI linker commands; these commands are
   6418 described here.
   6419 
   6420    In general, MRI scripts aren't of much use with the `a.out' object
   6421 file format, since it only has three sections and MRI scripts lack some
   6422 features to make use of them.
   6423 
   6424    You can specify a file containing an MRI-compatible script using the
   6425 `-c' command-line option.
   6426 
   6427    Each command in an MRI-compatible script occupies its own line; each
   6428 command line starts with the keyword that identifies the command (though
   6429 blank lines are also allowed for punctuation).  If a line of an
   6430 MRI-compatible script begins with an unrecognized keyword, `ld' issues
   6431 a warning message, but continues processing the script.
   6432 
   6433    Lines beginning with `*' are comments.
   6434 
   6435    You can write these commands using all upper-case letters, or all
   6436 lower case; for example, `chip' is the same as `CHIP'.  The following
   6437 list shows only the upper-case form of each command.
   6438 
   6439 `ABSOLUTE SECNAME'
   6440 `ABSOLUTE SECNAME, SECNAME, ... SECNAME'
   6441      Normally, `ld' includes in the output file all sections from all
   6442      the input files.  However, in an MRI-compatible script, you can
   6443      use the `ABSOLUTE' command to restrict the sections that will be
   6444      present in your output program.  If the `ABSOLUTE' command is used
   6445      at all in a script, then only the sections named explicitly in
   6446      `ABSOLUTE' commands will appear in the linker output.  You can
   6447      still use other input sections (whatever you select on the command
   6448      line, or using `LOAD') to resolve addresses in the output file.
   6449 
   6450 `ALIAS OUT-SECNAME, IN-SECNAME'
   6451      Use this command to place the data from input section IN-SECNAME
   6452      in a section called OUT-SECNAME in the linker output file.
   6453 
   6454      IN-SECNAME may be an integer.
   6455 
   6456 `ALIGN SECNAME = EXPRESSION'
   6457      Align the section called SECNAME to EXPRESSION.  The EXPRESSION
   6458      should be a power of two.
   6459 
   6460 `BASE EXPRESSION'
   6461      Use the value of EXPRESSION as the lowest address (other than
   6462      absolute addresses) in the output file.
   6463 
   6464 `CHIP EXPRESSION'
   6465 `CHIP EXPRESSION, EXPRESSION'
   6466      This command does nothing; it is accepted only for compatibility.
   6467 
   6468 `END'
   6469      This command does nothing whatever; it's only accepted for
   6470      compatibility.
   6471 
   6472 `FORMAT OUTPUT-FORMAT'
   6473      Similar to the `OUTPUT_FORMAT' command in the more general linker
   6474      language, but restricted to one of these output formats:
   6475 
   6476        1. S-records, if OUTPUT-FORMAT is `S'
   6477 
   6478        2. IEEE, if OUTPUT-FORMAT is `IEEE'
   6479 
   6480        3. COFF (the `coff-m68k' variant in BFD), if OUTPUT-FORMAT is
   6481           `COFF'
   6482 
   6483 `LIST ANYTHING...'
   6484      Print (to the standard output file) a link map, as produced by the
   6485      `ld' command-line option `-M'.
   6486 
   6487      The keyword `LIST' may be followed by anything on the same line,
   6488      with no change in its effect.
   6489 
   6490 `LOAD FILENAME'
   6491 `LOAD FILENAME, FILENAME, ... FILENAME'
   6492      Include one or more object file FILENAME in the link; this has the
   6493      same effect as specifying FILENAME directly on the `ld' command
   6494      line.
   6495 
   6496 `NAME OUTPUT-NAME'
   6497      OUTPUT-NAME is the name for the program produced by `ld'; the
   6498      MRI-compatible command `NAME' is equivalent to the command-line
   6499      option `-o' or the general script language command `OUTPUT'.
   6500 
   6501 `ORDER SECNAME, SECNAME, ... SECNAME'
   6502 `ORDER SECNAME SECNAME SECNAME'
   6503      Normally, `ld' orders the sections in its output file in the order
   6504      in which they first appear in the input files.  In an
   6505      MRI-compatible script, you can override this ordering with the
   6506      `ORDER' command.  The sections you list with `ORDER' will appear
   6507      first in your output file, in the order specified.
   6508 
   6509 `PUBLIC NAME=EXPRESSION'
   6510 `PUBLIC NAME,EXPRESSION'
   6511 `PUBLIC NAME EXPRESSION'
   6512      Supply a value (EXPRESSION) for external symbol NAME used in the
   6513      linker input files.
   6514 
   6515 `SECT SECNAME, EXPRESSION'
   6516 `SECT SECNAME=EXPRESSION'
   6517 `SECT SECNAME EXPRESSION'
   6518      You can use any of these three forms of the `SECT' command to
   6519      specify the start address (EXPRESSION) for section SECNAME.  If
   6520      you have more than one `SECT' statement for the same SECNAME, only
   6521      the _first_ sets the start address.
   6522 
   6523 
   6524 File: ld.info,  Node: GNU Free Documentation License,  Next: LD Index,  Prev: MRI,  Up: Top
   6525 
   6526 Appendix B GNU Free Documentation License
   6527 *****************************************
   6528 
   6529                      Version 1.3, 3 November 2008
   6530 
   6531      Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
   6532      `http://fsf.org/'
   6533 
   6534      Everyone is permitted to copy and distribute verbatim copies
   6535      of this license document, but changing it is not allowed.
   6536 
   6537   0. PREAMBLE
   6538 
   6539      The purpose of this License is to make a manual, textbook, or other
   6540      functional and useful document "free" in the sense of freedom: to
   6541      assure everyone the effective freedom to copy and redistribute it,
   6542      with or without modifying it, either commercially or
   6543      noncommercially.  Secondarily, this License preserves for the
   6544      author and publisher a way to get credit for their work, while not
   6545      being considered responsible for modifications made by others.
   6546 
   6547      This License is a kind of "copyleft", which means that derivative
   6548      works of the document must themselves be free in the same sense.
   6549      It complements the GNU General Public License, which is a copyleft
   6550      license designed for free software.
   6551 
   6552      We have designed this License in order to use it for manuals for
   6553      free software, because free software needs free documentation: a
   6554      free program should come with manuals providing the same freedoms
   6555      that the software does.  But this License is not limited to
   6556      software manuals; it can be used for any textual work, regardless
   6557      of subject matter or whether it is published as a printed book.
   6558      We recommend this License principally for works whose purpose is
   6559      instruction or reference.
   6560 
   6561   1. APPLICABILITY AND DEFINITIONS
   6562 
   6563      This License applies to any manual or other work, in any medium,
   6564      that contains a notice placed by the copyright holder saying it
   6565      can be distributed under the terms of this License.  Such a notice
   6566      grants a world-wide, royalty-free license, unlimited in duration,
   6567      to use that work under the conditions stated herein.  The
   6568      "Document", below, refers to any such manual or work.  Any member
   6569      of the public is a licensee, and is addressed as "you".  You
   6570      accept the license if you copy, modify or distribute the work in a
   6571      way requiring permission under copyright law.
   6572 
   6573      A "Modified Version" of the Document means any work containing the
   6574      Document or a portion of it, either copied verbatim, or with
   6575      modifications and/or translated into another language.
   6576 
   6577      A "Secondary Section" is a named appendix or a front-matter section
   6578      of the Document that deals exclusively with the relationship of the
   6579      publishers or authors of the Document to the Document's overall
   6580      subject (or to related matters) and contains nothing that could
   6581      fall directly within that overall subject.  (Thus, if the Document
   6582      is in part a textbook of mathematics, a Secondary Section may not
   6583      explain any mathematics.)  The relationship could be a matter of
   6584      historical connection with the subject or with related matters, or
   6585      of legal, commercial, philosophical, ethical or political position
   6586      regarding them.
   6587 
   6588      The "Invariant Sections" are certain Secondary Sections whose
   6589      titles are designated, as being those of Invariant Sections, in
   6590      the notice that says that the Document is released under this
   6591      License.  If a section does not fit the above definition of
   6592      Secondary then it is not allowed to be designated as Invariant.
   6593      The Document may contain zero Invariant Sections.  If the Document
   6594      does not identify any Invariant Sections then there are none.
   6595 
   6596      The "Cover Texts" are certain short passages of text that are
   6597      listed, as Front-Cover Texts or Back-Cover Texts, in the notice
   6598      that says that the Document is released under this License.  A
   6599      Front-Cover Text may be at most 5 words, and a Back-Cover Text may
   6600      be at most 25 words.
   6601 
   6602      A "Transparent" copy of the Document means a machine-readable copy,
   6603      represented in a format whose specification is available to the
   6604      general public, that is suitable for revising the document
   6605      straightforwardly with generic text editors or (for images
   6606      composed of pixels) generic paint programs or (for drawings) some
   6607      widely available drawing editor, and that is suitable for input to
   6608      text formatters or for automatic translation to a variety of
   6609      formats suitable for input to text formatters.  A copy made in an
   6610      otherwise Transparent file format whose markup, or absence of
   6611      markup, has been arranged to thwart or discourage subsequent
   6612      modification by readers is not Transparent.  An image format is
   6613      not Transparent if used for any substantial amount of text.  A
   6614      copy that is not "Transparent" is called "Opaque".
   6615 
   6616      Examples of suitable formats for Transparent copies include plain
   6617      ASCII without markup, Texinfo input format, LaTeX input format,
   6618      SGML or XML using a publicly available DTD, and
   6619      standard-conforming simple HTML, PostScript or PDF designed for
   6620      human modification.  Examples of transparent image formats include
   6621      PNG, XCF and JPG.  Opaque formats include proprietary formats that
   6622      can be read and edited only by proprietary word processors, SGML or
   6623      XML for which the DTD and/or processing tools are not generally
   6624      available, and the machine-generated HTML, PostScript or PDF
   6625      produced by some word processors for output purposes only.
   6626 
   6627      The "Title Page" means, for a printed book, the title page itself,
   6628      plus such following pages as are needed to hold, legibly, the
   6629      material this License requires to appear in the title page.  For
   6630      works in formats which do not have any title page as such, "Title
   6631      Page" means the text near the most prominent appearance of the
   6632      work's title, preceding the beginning of the body of the text.
   6633 
   6634      The "publisher" means any person or entity that distributes copies
   6635      of the Document to the public.
   6636 
   6637      A section "Entitled XYZ" means a named subunit of the Document
   6638      whose title either is precisely XYZ or contains XYZ in parentheses
   6639      following text that translates XYZ in another language.  (Here XYZ
   6640      stands for a specific section name mentioned below, such as
   6641      "Acknowledgements", "Dedications", "Endorsements", or "History".)
   6642      To "Preserve the Title" of such a section when you modify the
   6643      Document means that it remains a section "Entitled XYZ" according
   6644      to this definition.
   6645 
   6646      The Document may include Warranty Disclaimers next to the notice
   6647      which states that this License applies to the Document.  These
   6648      Warranty Disclaimers are considered to be included by reference in
   6649      this License, but only as regards disclaiming warranties: any other
   6650      implication that these Warranty Disclaimers may have is void and
   6651      has no effect on the meaning of this License.
   6652 
   6653   2. VERBATIM COPYING
   6654 
   6655      You may copy and distribute the Document in any medium, either
   6656      commercially or noncommercially, provided that this License, the
   6657      copyright notices, and the license notice saying this License
   6658      applies to the Document are reproduced in all copies, and that you
   6659      add no other conditions whatsoever to those of this License.  You
   6660      may not use technical measures to obstruct or control the reading
   6661      or further copying of the copies you make or distribute.  However,
   6662      you may accept compensation in exchange for copies.  If you
   6663      distribute a large enough number of copies you must also follow
   6664      the conditions in section 3.
   6665 
   6666      You may also lend copies, under the same conditions stated above,
   6667      and you may publicly display copies.
   6668 
   6669   3. COPYING IN QUANTITY
   6670 
   6671      If you publish printed copies (or copies in media that commonly
   6672      have printed covers) of the Document, numbering more than 100, and
   6673      the Document's license notice requires Cover Texts, you must
   6674      enclose the copies in covers that carry, clearly and legibly, all
   6675      these Cover Texts: Front-Cover Texts on the front cover, and
   6676      Back-Cover Texts on the back cover.  Both covers must also clearly
   6677      and legibly identify you as the publisher of these copies.  The
   6678      front cover must present the full title with all words of the
   6679      title equally prominent and visible.  You may add other material
   6680      on the covers in addition.  Copying with changes limited to the
   6681      covers, as long as they preserve the title of the Document and
   6682      satisfy these conditions, can be treated as verbatim copying in
   6683      other respects.
   6684 
   6685      If the required texts for either cover are too voluminous to fit
   6686      legibly, you should put the first ones listed (as many as fit
   6687      reasonably) on the actual cover, and continue the rest onto
   6688      adjacent pages.
   6689 
   6690      If you publish or distribute Opaque copies of the Document
   6691      numbering more than 100, you must either include a
   6692      machine-readable Transparent copy along with each Opaque copy, or
   6693      state in or with each Opaque copy a computer-network location from
   6694      which the general network-using public has access to download
   6695      using public-standard network protocols a complete Transparent
   6696      copy of the Document, free of added material.  If you use the
   6697      latter option, you must take reasonably prudent steps, when you
   6698      begin distribution of Opaque copies in quantity, to ensure that
   6699      this Transparent copy will remain thus accessible at the stated
   6700      location until at least one year after the last time you
   6701      distribute an Opaque copy (directly or through your agents or
   6702      retailers) of that edition to the public.
   6703 
   6704      It is requested, but not required, that you contact the authors of
   6705      the Document well before redistributing any large number of
   6706      copies, to give them a chance to provide you with an updated
   6707      version of the Document.
   6708 
   6709   4. MODIFICATIONS
   6710 
   6711      You may copy and distribute a Modified Version of the Document
   6712      under the conditions of sections 2 and 3 above, provided that you
   6713      release the Modified Version under precisely this License, with
   6714      the Modified Version filling the role of the Document, thus
   6715      licensing distribution and modification of the Modified Version to
   6716      whoever possesses a copy of it.  In addition, you must do these
   6717      things in the Modified Version:
   6718 
   6719        A. Use in the Title Page (and on the covers, if any) a title
   6720           distinct from that of the Document, and from those of
   6721           previous versions (which should, if there were any, be listed
   6722           in the History section of the Document).  You may use the
   6723           same title as a previous version if the original publisher of
   6724           that version gives permission.
   6725 
   6726        B. List on the Title Page, as authors, one or more persons or
   6727           entities responsible for authorship of the modifications in
   6728           the Modified Version, together with at least five of the
   6729           principal authors of the Document (all of its principal
   6730           authors, if it has fewer than five), unless they release you
   6731           from this requirement.
   6732 
   6733        C. State on the Title page the name of the publisher of the
   6734           Modified Version, as the publisher.
   6735 
   6736        D. Preserve all the copyright notices of the Document.
   6737 
   6738        E. Add an appropriate copyright notice for your modifications
   6739           adjacent to the other copyright notices.
   6740 
   6741        F. Include, immediately after the copyright notices, a license
   6742           notice giving the public permission to use the Modified
   6743           Version under the terms of this License, in the form shown in
   6744           the Addendum below.
   6745 
   6746        G. Preserve in that license notice the full lists of Invariant
   6747           Sections and required Cover Texts given in the Document's
   6748           license notice.
   6749 
   6750        H. Include an unaltered copy of this License.
   6751 
   6752        I. Preserve the section Entitled "History", Preserve its Title,
   6753           and add to it an item stating at least the title, year, new
   6754           authors, and publisher of the Modified Version as given on
   6755           the Title Page.  If there is no section Entitled "History" in
   6756           the Document, create one stating the title, year, authors,
   6757           and publisher of the Document as given on its Title Page,
   6758           then add an item describing the Modified Version as stated in
   6759           the previous sentence.
   6760 
   6761        J. Preserve the network location, if any, given in the Document
   6762           for public access to a Transparent copy of the Document, and
   6763           likewise the network locations given in the Document for
   6764           previous versions it was based on.  These may be placed in
   6765           the "History" section.  You may omit a network location for a
   6766           work that was published at least four years before the
   6767           Document itself, or if the original publisher of the version
   6768           it refers to gives permission.
   6769 
   6770        K. For any section Entitled "Acknowledgements" or "Dedications",
   6771           Preserve the Title of the section, and preserve in the
   6772           section all the substance and tone of each of the contributor
   6773           acknowledgements and/or dedications given therein.
   6774 
   6775        L. Preserve all the Invariant Sections of the Document,
   6776           unaltered in their text and in their titles.  Section numbers
   6777           or the equivalent are not considered part of the section
   6778           titles.
   6779 
   6780        M. Delete any section Entitled "Endorsements".  Such a section
   6781           may not be included in the Modified Version.
   6782 
   6783        N. Do not retitle any existing section to be Entitled
   6784           "Endorsements" or to conflict in title with any Invariant
   6785           Section.
   6786 
   6787        O. Preserve any Warranty Disclaimers.
   6788 
   6789      If the Modified Version includes new front-matter sections or
   6790      appendices that qualify as Secondary Sections and contain no
   6791      material copied from the Document, you may at your option
   6792      designate some or all of these sections as invariant.  To do this,
   6793      add their titles to the list of Invariant Sections in the Modified
   6794      Version's license notice.  These titles must be distinct from any
   6795      other section titles.
   6796 
   6797      You may add a section Entitled "Endorsements", provided it contains
   6798      nothing but endorsements of your Modified Version by various
   6799      parties--for example, statements of peer review or that the text
   6800      has been approved by an organization as the authoritative
   6801      definition of a standard.
   6802 
   6803      You may add a passage of up to five words as a Front-Cover Text,
   6804      and a passage of up to 25 words as a Back-Cover Text, to the end
   6805      of the list of Cover Texts in the Modified Version.  Only one
   6806      passage of Front-Cover Text and one of Back-Cover Text may be
   6807      added by (or through arrangements made by) any one entity.  If the
   6808      Document already includes a cover text for the same cover,
   6809      previously added by you or by arrangement made by the same entity
   6810      you are acting on behalf of, you may not add another; but you may
   6811      replace the old one, on explicit permission from the previous
   6812      publisher that added the old one.
   6813 
   6814      The author(s) and publisher(s) of the Document do not by this
   6815      License give permission to use their names for publicity for or to
   6816      assert or imply endorsement of any Modified Version.
   6817 
   6818   5. COMBINING DOCUMENTS
   6819 
   6820      You may combine the Document with other documents released under
   6821      this License, under the terms defined in section 4 above for
   6822      modified versions, provided that you include in the combination
   6823      all of the Invariant Sections of all of the original documents,
   6824      unmodified, and list them all as Invariant Sections of your
   6825      combined work in its license notice, and that you preserve all
   6826      their Warranty Disclaimers.
   6827 
   6828      The combined work need only contain one copy of this License, and
   6829      multiple identical Invariant Sections may be replaced with a single
   6830      copy.  If there are multiple Invariant Sections with the same name
   6831      but different contents, make the title of each such section unique
   6832      by adding at the end of it, in parentheses, the name of the
   6833      original author or publisher of that section if known, or else a
   6834      unique number.  Make the same adjustment to the section titles in
   6835      the list of Invariant Sections in the license notice of the
   6836      combined work.
   6837 
   6838      In the combination, you must combine any sections Entitled
   6839      "History" in the various original documents, forming one section
   6840      Entitled "History"; likewise combine any sections Entitled
   6841      "Acknowledgements", and any sections Entitled "Dedications".  You
   6842      must delete all sections Entitled "Endorsements."
   6843 
   6844   6. COLLECTIONS OF DOCUMENTS
   6845 
   6846      You may make a collection consisting of the Document and other
   6847      documents released under this License, and replace the individual
   6848      copies of this License in the various documents with a single copy
   6849      that is included in the collection, provided that you follow the
   6850      rules of this License for verbatim copying of each of the
   6851      documents in all other respects.
   6852 
   6853      You may extract a single document from such a collection, and
   6854      distribute it individually under this License, provided you insert
   6855      a copy of this License into the extracted document, and follow
   6856      this License in all other respects regarding verbatim copying of
   6857      that document.
   6858 
   6859   7. AGGREGATION WITH INDEPENDENT WORKS
   6860 
   6861      A compilation of the Document or its derivatives with other
   6862      separate and independent documents or works, in or on a volume of
   6863      a storage or distribution medium, is called an "aggregate" if the
   6864      copyright resulting from the compilation is not used to limit the
   6865      legal rights of the compilation's users beyond what the individual
   6866      works permit.  When the Document is included in an aggregate, this
   6867      License does not apply to the other works in the aggregate which
   6868      are not themselves derivative works of the Document.
   6869 
   6870      If the Cover Text requirement of section 3 is applicable to these
   6871      copies of the Document, then if the Document is less than one half
   6872      of the entire aggregate, the Document's Cover Texts may be placed
   6873      on covers that bracket the Document within the aggregate, or the
   6874      electronic equivalent of covers if the Document is in electronic
   6875      form.  Otherwise they must appear on printed covers that bracket
   6876      the whole aggregate.
   6877 
   6878   8. TRANSLATION
   6879 
   6880      Translation is considered a kind of modification, so you may
   6881      distribute translations of the Document under the terms of section
   6882      4.  Replacing Invariant Sections with translations requires special
   6883      permission from their copyright holders, but you may include
   6884      translations of some or all Invariant Sections in addition to the
   6885      original versions of these Invariant Sections.  You may include a
   6886      translation of this License, and all the license notices in the
   6887      Document, and any Warranty Disclaimers, provided that you also
   6888      include the original English version of this License and the
   6889      original versions of those notices and disclaimers.  In case of a
   6890      disagreement between the translation and the original version of
   6891      this License or a notice or disclaimer, the original version will
   6892      prevail.
   6893 
   6894      If a section in the Document is Entitled "Acknowledgements",
   6895      "Dedications", or "History", the requirement (section 4) to
   6896      Preserve its Title (section 1) will typically require changing the
   6897      actual title.
   6898 
   6899   9. TERMINATION
   6900 
   6901      You may not copy, modify, sublicense, or distribute the Document
   6902      except as expressly provided under this License.  Any attempt
   6903      otherwise to copy, modify, sublicense, or distribute it is void,
   6904      and will automatically terminate your rights under this License.
   6905 
   6906      However, if you cease all violation of this License, then your
   6907      license from a particular copyright holder is reinstated (a)
   6908      provisionally, unless and until the copyright holder explicitly
   6909      and finally terminates your license, and (b) permanently, if the
   6910      copyright holder fails to notify you of the violation by some
   6911      reasonable means prior to 60 days after the cessation.
   6912 
   6913      Moreover, your license from a particular copyright holder is
   6914      reinstated permanently if the copyright holder notifies you of the
   6915      violation by some reasonable means, this is the first time you have
   6916      received notice of violation of this License (for any work) from
   6917      that copyright holder, and you cure the violation prior to 30 days
   6918      after your receipt of the notice.
   6919 
   6920      Termination of your rights under this section does not terminate
   6921      the licenses of parties who have received copies or rights from
   6922      you under this License.  If your rights have been terminated and
   6923      not permanently reinstated, receipt of a copy of some or all of
   6924      the same material does not give you any rights to use it.
   6925 
   6926  10. FUTURE REVISIONS OF THIS LICENSE
   6927 
   6928      The Free Software Foundation may publish new, revised versions of
   6929      the GNU Free Documentation License from time to time.  Such new
   6930      versions will be similar in spirit to the present version, but may
   6931      differ in detail to address new problems or concerns.  See
   6932      `http://www.gnu.org/copyleft/'.
   6933 
   6934      Each version of the License is given a distinguishing version
   6935      number.  If the Document specifies that a particular numbered
   6936      version of this License "or any later version" applies to it, you
   6937      have the option of following the terms and conditions either of
   6938      that specified version or of any later version that has been
   6939      published (not as a draft) by the Free Software Foundation.  If
   6940      the Document does not specify a version number of this License,
   6941      you may choose any version ever published (not as a draft) by the
   6942      Free Software Foundation.  If the Document specifies that a proxy
   6943      can decide which future versions of this License can be used, that
   6944      proxy's public statement of acceptance of a version permanently
   6945      authorizes you to choose that version for the Document.
   6946 
   6947  11. RELICENSING
   6948 
   6949      "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
   6950      World Wide Web server that publishes copyrightable works and also
   6951      provides prominent facilities for anybody to edit those works.  A
   6952      public wiki that anybody can edit is an example of such a server.
   6953      A "Massive Multiauthor Collaboration" (or "MMC") contained in the
   6954      site means any set of copyrightable works thus published on the MMC
   6955      site.
   6956 
   6957      "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
   6958      license published by Creative Commons Corporation, a not-for-profit
   6959      corporation with a principal place of business in San Francisco,
   6960      California, as well as future copyleft versions of that license
   6961      published by that same organization.
   6962 
   6963      "Incorporate" means to publish or republish a Document, in whole or
   6964      in part, as part of another Document.
   6965 
   6966      An MMC is "eligible for relicensing" if it is licensed under this
   6967      License, and if all works that were first published under this
   6968      License somewhere other than this MMC, and subsequently
   6969      incorporated in whole or in part into the MMC, (1) had no cover
   6970      texts or invariant sections, and (2) were thus incorporated prior
   6971      to November 1, 2008.
   6972 
   6973      The operator of an MMC Site may republish an MMC contained in the
   6974      site under CC-BY-SA on the same site at any time before August 1,
   6975      2009, provided the MMC is eligible for relicensing.
   6976 
   6977 
   6978 ADDENDUM: How to use this License for your documents
   6979 ====================================================
   6980 
   6981 To use this License in a document you have written, include a copy of
   6982 the License in the document and put the following copyright and license
   6983 notices just after the title page:
   6984 
   6985        Copyright (C)  YEAR  YOUR NAME.
   6986        Permission is granted to copy, distribute and/or modify this document
   6987        under the terms of the GNU Free Documentation License, Version 1.3
   6988        or any later version published by the Free Software Foundation;
   6989        with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
   6990        Texts.  A copy of the license is included in the section entitled ``GNU
   6991        Free Documentation License''.
   6992 
   6993    If you have Invariant Sections, Front-Cover Texts and Back-Cover
   6994 Texts, replace the "with...Texts." line with this:
   6995 
   6996          with the Invariant Sections being LIST THEIR TITLES, with
   6997          the Front-Cover Texts being LIST, and with the Back-Cover Texts
   6998          being LIST.
   6999 
   7000    If you have Invariant Sections without Cover Texts, or some other
   7001 combination of the three, merge those two alternatives to suit the
   7002 situation.
   7003 
   7004    If your document contains nontrivial examples of program code, we
   7005 recommend releasing these examples in parallel under your choice of
   7006 free software license, such as the GNU General Public License, to
   7007 permit their use in free software.
   7008 
   7009 
   7010 File: ld.info,  Node: LD Index,  Prev: GNU Free Documentation License,  Up: Top
   7011 
   7012 LD Index
   7013 ********
   7014 
   7015 [index]
   7016 * Menu:
   7017 
   7018 * ":                                     Symbols.            (line    6)
   7019 * -(:                                    Options.            (line  696)
   7020 * --accept-unknown-input-arch:           Options.            (line  714)
   7021 * --add-needed:                          Options.            (line  738)
   7022 * --add-stdcall-alias:                   Options.            (line 1571)
   7023 * --allow-multiple-definition:           Options.            (line  984)
   7024 * --allow-shlib-undefined:               Options.            (line  990)
   7025 * --architecture=ARCH:                   Options.            (line  123)
   7026 * --as-needed:                           Options.            (line  724)
   7027 * --audit AUDITLIB:                      Options.            (line  112)
   7028 * --auxiliary=NAME:                      Options.            (line  255)
   7029 * --bank-window:                         Options.            (line 1980)
   7030 * --base-file:                           Options.            (line 1576)
   7031 * --be8:                                 ARM.                (line   28)
   7032 * --bss-plt:                             PowerPC ELF32.      (line   16)
   7033 * --build-id:                            Options.            (line 1533)
   7034 * --build-id=STYLE:                      Options.            (line 1533)
   7035 * --check-sections:                      Options.            (line  817)
   7036 * --copy-dt-needed-entries:              Options.            (line  829)
   7037 * --cref:                                Options.            (line  850)
   7038 * --default-imported-symver:             Options.            (line 1027)
   7039 * --default-script=SCRIPT:               Options.            (line  541)
   7040 * --default-symver:                      Options.            (line 1023)
   7041 * --defsym=SYMBOL=EXP:                   Options.            (line  878)
   7042 * --demangle[=STYLE]:                    Options.            (line  891)
   7043 * --depaudit AUDITLIB:                   Options.            (line  177)
   7044 * --disable-auto-image-base:             Options.            (line 1755)
   7045 * --disable-auto-import:                 Options.            (line 1890)
   7046 * --disable-long-section-names:          Options.            (line 1586)
   7047 * --disable-new-dtags:                   Options.            (line 1496)
   7048 * --disable-runtime-pseudo-reloc:        Options.            (line 1903)
   7049 * --disable-stdcall-fixup:               Options.            (line 1608)
   7050 * --discard-all:                         Options.            (line  587)
   7051 * --discard-locals:                      Options.            (line  591)
   7052 * --dll:                                 Options.            (line 1581)
   7053 * --dll-search-prefix:                   Options.            (line 1761)
   7054 * --dotsyms:                             PowerPC64 ELF64.    (line   33)
   7055 * --dynamic-linker=FILE:                 Options.            (line  904)
   7056 * --dynamic-list-cpp-new:                Options.            (line  809)
   7057 * --dynamic-list-cpp-typeinfo:           Options.            (line  813)
   7058 * --dynamic-list-data:                   Options.            (line  806)
   7059 * --dynamic-list=DYNAMIC-LIST-FILE:      Options.            (line  793)
   7060 * --dynamicbase:                         Options.            (line 1939)
   7061 * --eh-frame-hdr:                        Options.            (line 1492)
   7062 * --emit-relocs:                         Options.            (line  476)
   7063 * --emit-stack-syms:                     SPU ELF.            (line   46)
   7064 * --emit-stub-syms <1>:                  SPU ELF.            (line   15)
   7065 * --emit-stub-syms <2>:                  PowerPC64 ELF64.    (line   29)
   7066 * --emit-stub-syms:                      PowerPC ELF32.      (line   47)
   7067 * --enable-auto-image-base:              Options.            (line 1747)
   7068 * --enable-auto-import:                  Options.            (line 1770)
   7069 * --enable-extra-pe-debug:               Options.            (line 1908)
   7070 * --enable-long-section-names:           Options.            (line 1586)
   7071 * --enable-new-dtags:                    Options.            (line 1496)
   7072 * --enable-runtime-pseudo-reloc:         Options.            (line 1895)
   7073 * --enable-stdcall-fixup:                Options.            (line 1608)
   7074 * --entry=ENTRY:                         Options.            (line  187)
   7075 * --error-unresolved-symbols:            Options.            (line 1445)
   7076 * --exclude-all-symbols:                 Options.            (line 1662)
   7077 * --exclude-libs:                        Options.            (line  197)
   7078 * --exclude-modules-for-implib:          Options.            (line  208)
   7079 * --exclude-symbols:                     Options.            (line 1656)
   7080 * --export-all-symbols:                  Options.            (line 1632)
   7081 * --export-dynamic:                      Options.            (line  221)
   7082 * --extra-overlay-stubs:                 SPU ELF.            (line   19)
   7083 * --fatal-warnings:                      Options.            (line  911)
   7084 * --file-alignment:                      Options.            (line 1666)
   7085 * --filter=NAME:                         Options.            (line  276)
   7086 * --fix-cortex-a8:                       i960.               (line   39)
   7087 * --fix-v4bx:                            ARM.                (line   49)
   7088 * --fix-v4bx-interworking:               ARM.                (line   62)
   7089 * --force-dynamic:                       Options.            (line  485)
   7090 * --force-exe-suffix:                    Options.            (line  916)
   7091 * --forceinteg:                          Options.            (line 1944)
   7092 * --format=FORMAT:                       Options.            (line  134)
   7093 * --format=VERSION:                      TI COFF.            (line    6)
   7094 * --gc-sections:                         Options.            (line  926)
   7095 * --got:                                 Options.            (line 1993)
   7096 * --got=TYPE:                            M68K.               (line    6)
   7097 * --gpsize=VALUE:                        Options.            (line  309)
   7098 * --hash-size=NUMBER:                    Options.            (line 1505)
   7099 * --hash-style=STYLE:                    Options.            (line 1513)
   7100 * --heap:                                Options.            (line 1672)
   7101 * --help:                                Options.            (line  957)
   7102 * --image-base:                          Options.            (line 1679)
   7103 * --just-symbols=FILE:                   Options.            (line  508)
   7104 * --kill-at:                             Options.            (line 1688)
   7105 * --large-address-aware:                 Options.            (line 1693)
   7106 * --leading-underscore:                  Options.            (line 1626)
   7107 * --library-path=DIR:                    Options.            (line  368)
   7108 * --library=NAMESPEC:                    Options.            (line  335)
   7109 * --local-store=lo:hi:                   SPU ELF.            (line   24)
   7110 * --major-image-version:                 Options.            (line 1702)
   7111 * --major-os-version:                    Options.            (line 1707)
   7112 * --major-subsystem-version:             Options.            (line 1711)
   7113 * --merge-exidx-entries:                 i960.               (line   48)
   7114 * --minor-image-version:                 Options.            (line 1716)
   7115 * --minor-os-version:                    Options.            (line 1721)
   7116 * --minor-subsystem-version:             Options.            (line 1725)
   7117 * --mri-script=MRI-CMDFILE:              Options.            (line  158)
   7118 * --multi-subspace:                      HPPA ELF32.         (line    6)
   7119 * --nmagic:                              Options.            (line  439)
   7120 * --no-accept-unknown-input-arch:        Options.            (line  714)
   7121 * --no-add-needed:                       Options.            (line  738)
   7122 * --no-allow-shlib-undefined:            Options.            (line  990)
   7123 * --no-as-needed:                        Options.            (line  724)
   7124 * --no-bind:                             Options.            (line 1958)
   7125 * --no-check-sections:                   Options.            (line  817)
   7126 * --no-copy-dt-needed-entries:           Options.            (line  829)
   7127 * --no-define-common:                    Options.            (line  862)
   7128 * --no-demangle:                         Options.            (line  891)
   7129 * --no-dotsyms:                          PowerPC64 ELF64.    (line   33)
   7130 * --no-enum-size-warning:                ARM.                (line  111)
   7131 * --no-export-dynamic:                   Options.            (line  221)
   7132 * --no-fatal-warnings:                   Options.            (line  911)
   7133 * --no-fix-cortex-a8:                    i960.               (line   39)
   7134 * --no-gc-sections:                      Options.            (line  926)
   7135 * --no-isolation:                        Options.            (line 1951)
   7136 * --no-keep-memory:                      Options.            (line  969)
   7137 * --no-leading-underscore:               Options.            (line 1626)
   7138 * --no-merge-exidx-entries:              i960.               (line   48)
   7139 * --no-multi-toc:                        PowerPC64 ELF64.    (line   74)
   7140 * --no-omagic:                           Options.            (line  454)
   7141 * --no-opd-optimize:                     PowerPC64 ELF64.    (line   48)
   7142 * --no-overlays:                         SPU ELF.            (line    9)
   7143 * --no-print-gc-sections:                Options.            (line  948)
   7144 * --no-seh:                              Options.            (line 1954)
   7145 * --no-tls-optimize <1>:                 PowerPC64 ELF64.    (line   43)
   7146 * --no-tls-optimize:                     PowerPC ELF32.      (line   51)
   7147 * --no-toc-optimize:                     PowerPC64 ELF64.    (line   60)
   7148 * --no-trampoline:                       Options.            (line 1974)
   7149 * --no-undefined:                        Options.            (line  976)
   7150 * --no-undefined-version:                Options.            (line 1018)
   7151 * --no-warn-mismatch:                    Options.            (line 1031)
   7152 * --no-warn-search-mismatch:             Options.            (line 1040)
   7153 * --no-wchar-size-warning:               ARM.                (line  118)
   7154 * --no-whole-archive:                    Options.            (line 1044)
   7155 * --noinhibit-exec:                      Options.            (line 1048)
   7156 * --non-overlapping-opd:                 PowerPC64 ELF64.    (line   54)
   7157 * --nxcompat:                            Options.            (line 1947)
   7158 * --oformat=OUTPUT-FORMAT:               Options.            (line 1060)
   7159 * --omagic:                              Options.            (line  445)
   7160 * --out-implib:                          Options.            (line 1738)
   7161 * --output-def:                          Options.            (line 1730)
   7162 * --output=OUTPUT:                       Options.            (line  460)
   7163 * --pic-executable:                      Options.            (line 1073)
   7164 * --pic-veneer:                          ARM.                (line  124)
   7165 * --plugin:                              SPU ELF.            (line    6)
   7166 * --print-gc-sections:                   Options.            (line  948)
   7167 * --print-map:                           Options.            (line  402)
   7168 * --reduce-memory-overheads:             Options.            (line 1519)
   7169 * --relax:                               Options.            (line 1089)
   7170 * --relax on i960:                       i960.               (line   31)
   7171 * --relax on PowerPC:                    PowerPC ELF32.      (line    6)
   7172 * --relax on Xtensa:                     Xtensa.             (line   27)
   7173 * --relocatable:                         Options.            (line  489)
   7174 * --retain-symbols-file=FILENAME:        Options.            (line 1115)
   7175 * --script=SCRIPT:                       Options.            (line  532)
   7176 * --sdata-got:                           PowerPC ELF32.      (line   33)
   7177 * --section-alignment:                   Options.            (line 1913)
   7178 * --section-start=SECTIONNAME=ORG:       Options.            (line 1271)
   7179 * --secure-plt:                          PowerPC ELF32.      (line   26)
   7180 * --sort-common:                         Options.            (line 1213)
   7181 * --sort-section=alignment:              Options.            (line 1228)
   7182 * --sort-section=name:                   Options.            (line 1224)
   7183 * --split-by-file:                       Options.            (line 1232)
   7184 * --split-by-reloc:                      Options.            (line 1237)
   7185 * --stack:                               Options.            (line 1919)
   7186 * --stack-analysis:                      SPU ELF.            (line   29)
   7187 * --stats:                               Options.            (line 1250)
   7188 * --strip-all:                           Options.            (line  519)
   7189 * --strip-debug:                         Options.            (line  523)
   7190 * --stub-group-size:                     PowerPC64 ELF64.    (line    6)
   7191 * --stub-group-size=N <1>:               HPPA ELF32.         (line   12)
   7192 * --stub-group-size=N:                   ARM.                (line  129)
   7193 * --subsystem:                           Options.            (line 1926)
   7194 * --support-old-code:                    ARM.                (line    6)
   7195 * --sysroot=DIRECTORY:                   Options.            (line 1254)
   7196 * --target-help:                         Options.            (line  961)
   7197 * --target1-abs:                         ARM.                (line   32)
   7198 * --target1-rel:                         ARM.                (line   32)
   7199 * --target2=TYPE:                        ARM.                (line   37)
   7200 * --thumb-entry=ENTRY:                   ARM.                (line   17)
   7201 * --trace:                               Options.            (line  528)
   7202 * --trace-symbol=SYMBOL:                 Options.            (line  597)
   7203 * --traditional-format:                  Options.            (line 1259)
   7204 * --tsaware:                             Options.            (line 1964)
   7205 * --undefined=SYMBOL:                    Options.            (line  554)
   7206 * --unique[=SECTION]:                    Options.            (line  572)
   7207 * --unresolved-symbols:                  Options.            (line 1290)
   7208 * --use-blx:                             ARM.                (line   74)
   7209 * --use-nul-prefixed-import-tables:      ARM.                (line   23)
   7210 * --verbose:                             Options.            (line 1319)
   7211 * --version:                             Options.            (line  581)
   7212 * --version-script=VERSION-SCRIPTFILE:   Options.            (line 1325)
   7213 * --vfp11-denorm-fix:                    ARM.                (line   83)
   7214 * --warn-alternate-em:                   Options.            (line 1437)
   7215 * --warn-common:                         Options.            (line 1336)
   7216 * --warn-constructors:                   Options.            (line 1404)
   7217 * --warn-multiple-gp:                    Options.            (line 1409)
   7218 * --warn-once:                           Options.            (line 1423)
   7219 * --warn-section-align:                  Options.            (line 1427)
   7220 * --warn-shared-textrel:                 Options.            (line 1434)
   7221 * --warn-unresolved-symbols:             Options.            (line 1440)
   7222 * --wdmdriver:                           Options.            (line 1961)
   7223 * --whole-archive:                       Options.            (line 1449)
   7224 * --wrap=SYMBOL:                         Options.            (line 1463)
   7225 * -A ARCH:                               Options.            (line  122)
   7226 * -a KEYWORD:                            Options.            (line  105)
   7227 * -assert KEYWORD:                       Options.            (line  745)
   7228 * -b FORMAT:                             Options.            (line  134)
   7229 * -Bdynamic:                             Options.            (line  748)
   7230 * -Bgroup:                               Options.            (line  758)
   7231 * -Bshareable:                           Options.            (line 1206)
   7232 * -Bstatic:                              Options.            (line  765)
   7233 * -Bsymbolic:                            Options.            (line  780)
   7234 * -Bsymbolic-functions:                  Options.            (line  787)
   7235 * -c MRI-CMDFILE:                        Options.            (line  158)
   7236 * -call_shared:                          Options.            (line  748)
   7237 * -d:                                    Options.            (line  168)
   7238 * -dc:                                   Options.            (line  168)
   7239 * -dn:                                   Options.            (line  765)
   7240 * -dp:                                   Options.            (line  168)
   7241 * -dT SCRIPT:                            Options.            (line  541)
   7242 * -dy:                                   Options.            (line  748)
   7243 * -E:                                    Options.            (line  221)
   7244 * -e ENTRY:                              Options.            (line  187)
   7245 * -EB:                                   Options.            (line  248)
   7246 * -EL:                                   Options.            (line  251)
   7247 * -F NAME:                               Options.            (line  276)
   7248 * -f NAME:                               Options.            (line  255)
   7249 * -fini=NAME:                            Options.            (line  300)
   7250 * -g:                                    Options.            (line  306)
   7251 * -G VALUE:                              Options.            (line  309)
   7252 * -h NAME:                               Options.            (line  317)
   7253 * -i:                                    Options.            (line  326)
   7254 * -IFILE:                                Options.            (line  904)
   7255 * -init=NAME:                            Options.            (line  329)
   7256 * -L DIR:                                Options.            (line  368)
   7257 * -l NAMESPEC:                           Options.            (line  335)
   7258 * -M:                                    Options.            (line  402)
   7259 * -m EMULATION:                          Options.            (line  392)
   7260 * -Map=MAPFILE:                          Options.            (line  965)
   7261 * -N:                                    Options.            (line  445)
   7262 * -n:                                    Options.            (line  439)
   7263 * -no-relax:                             Options.            (line 1089)
   7264 * -non_shared:                           Options.            (line  765)
   7265 * -nostdlib:                             Options.            (line 1054)
   7266 * -O LEVEL:                              Options.            (line  466)
   7267 * -o OUTPUT:                             Options.            (line  460)
   7268 * -P AUDITLIB:                           Options.            (line  177)
   7269 * -pie:                                  Options.            (line 1073)
   7270 * -q:                                    Options.            (line  476)
   7271 * -qmagic:                               Options.            (line 1083)
   7272 * -Qy:                                   Options.            (line 1086)
   7273 * -r:                                    Options.            (line  489)
   7274 * -R FILE:                               Options.            (line  508)
   7275 * -rpath-link=DIR:                       Options.            (line 1151)
   7276 * -rpath=DIR:                            Options.            (line 1129)
   7277 * -S:                                    Options.            (line  523)
   7278 * -s:                                    Options.            (line  519)
   7279 * -shared:                               Options.            (line 1206)
   7280 * -soname=NAME:                          Options.            (line  317)
   7281 * -static:                               Options.            (line  765)
   7282 * -t:                                    Options.            (line  528)
   7283 * -T SCRIPT:                             Options.            (line  532)
   7284 * -Tbss=ORG:                             Options.            (line 1280)
   7285 * -Tdata=ORG:                            Options.            (line 1280)
   7286 * -Ttext-segment=ORG:                    Options.            (line 1286)
   7287 * -Ttext=ORG:                            Options.            (line 1280)
   7288 * -u SYMBOL:                             Options.            (line  554)
   7289 * -Ur:                                   Options.            (line  562)
   7290 * -V:                                    Options.            (line  581)
   7291 * -v:                                    Options.            (line  581)
   7292 * -X:                                    Options.            (line  591)
   7293 * -x:                                    Options.            (line  587)
   7294 * -Y PATH:                               Options.            (line  606)
   7295 * -y SYMBOL:                             Options.            (line  597)
   7296 * -z defs:                               Options.            (line  976)
   7297 * -z KEYWORD:                            Options.            (line  610)
   7298 * -z muldefs:                            Options.            (line  984)
   7299 * .:                                     Location Counter.   (line    6)
   7300 * /DISCARD/:                             Output Section Discarding.
   7301                                                              (line   21)
   7302 * :PHDR:                                 Output Section Phdr.
   7303                                                              (line    6)
   7304 * =FILLEXP:                              Output Section Fill.
   7305                                                              (line    6)
   7306 * >REGION:                               Output Section Region.
   7307                                                              (line    6)
   7308 * [COMMON]:                              Input Section Common.
   7309                                                              (line   29)
   7310 * ABSOLUTE (MRI):                        MRI.                (line   33)
   7311 * absolute and relocatable symbols:      Expression Section. (line    6)
   7312 * absolute expressions:                  Expression Section. (line    6)
   7313 * ABSOLUTE(EXP):                         Builtin Functions.  (line   10)
   7314 * ADDR(SECTION):                         Builtin Functions.  (line   17)
   7315 * address, section:                      Output Section Address.
   7316                                                              (line    6)
   7317 * ALIAS (MRI):                           MRI.                (line   44)
   7318 * ALIGN (MRI):                           MRI.                (line   50)
   7319 * align expression:                      Builtin Functions.  (line   38)
   7320 * align location counter:                Builtin Functions.  (line   38)
   7321 * ALIGN(ALIGN):                          Builtin Functions.  (line   38)
   7322 * ALIGN(EXP,ALIGN):                      Builtin Functions.  (line   38)
   7323 * ALIGN(SECTION_ALIGN):                  Forced Output Alignment.
   7324                                                              (line    6)
   7325 * aligned common symbols:                WIN32.              (line  424)
   7326 * ALIGNOF(SECTION):                      Builtin Functions.  (line   63)
   7327 * allocating memory:                     MEMORY.             (line    6)
   7328 * architecture:                          Miscellaneous Commands.
   7329                                                              (line   72)
   7330 * architectures:                         Options.            (line  122)
   7331 * archive files, from cmd line:          Options.            (line  335)
   7332 * archive search path in linker script:  File Commands.      (line   74)
   7333 * arithmetic:                            Expressions.        (line    6)
   7334 * arithmetic operators:                  Operators.          (line    6)
   7335 * ARM interworking support:              ARM.                (line    6)
   7336 * AS_NEEDED(FILES):                      File Commands.      (line   54)
   7337 * ASSERT:                                Miscellaneous Commands.
   7338                                                              (line    9)
   7339 * assertion in linker script:            Miscellaneous Commands.
   7340                                                              (line    9)
   7341 * assignment in scripts:                 Assignments.        (line    6)
   7342 * AT(LMA):                               Output Section LMA. (line    6)
   7343 * AT>LMA_REGION:                         Output Section LMA. (line    6)
   7344 * automatic data imports:                WIN32.              (line  191)
   7345 * back end:                              BFD.                (line    6)
   7346 * BASE (MRI):                            MRI.                (line   54)
   7347 * BE8:                                   ARM.                (line   28)
   7348 * BFD canonical format:                  Canonical format.   (line   11)
   7349 * BFD requirements:                      BFD.                (line   16)
   7350 * big-endian objects:                    Options.            (line  248)
   7351 * binary input format:                   Options.            (line  134)
   7352 * BLOCK(EXP):                            Builtin Functions.  (line   76)
   7353 * bug criteria:                          Bug Criteria.       (line    6)
   7354 * bug reports:                           Bug Reporting.      (line    6)
   7355 * bugs in ld:                            Reporting Bugs.     (line    6)
   7356 * BYTE(EXPRESSION):                      Output Section Data.
   7357                                                              (line    6)
   7358 * C++ constructors, arranging in link:   Output Section Keywords.
   7359                                                              (line   19)
   7360 * CHIP (MRI):                            MRI.                (line   58)
   7361 * COLLECT_NO_DEMANGLE:                   Environment.        (line   29)
   7362 * combining symbols, warnings on:        Options.            (line 1336)
   7363 * command files:                         Scripts.            (line    6)
   7364 * command line:                          Options.            (line    6)
   7365 * common allocation:                     Options.            (line  168)
   7366 * common allocation in linker script:    Miscellaneous Commands.
   7367                                                              (line   20)
   7368 * common symbol placement:               Input Section Common.
   7369                                                              (line    6)
   7370 * COMMONPAGESIZE:                        Symbolic Constants. (line   13)
   7371 * compatibility, MRI:                    Options.            (line  158)
   7372 * CONSTANT:                              Symbolic Constants. (line    6)
   7373 * constants in linker scripts:           Constants.          (line    6)
   7374 * constraints on output sections:        Output Section Constraint.
   7375                                                              (line    6)
   7376 * CONSTRUCTORS:                          Output Section Keywords.
   7377                                                              (line   19)
   7378 * constructors:                          Options.            (line  562)
   7379 * constructors, arranging in link:       Output Section Keywords.
   7380                                                              (line   19)
   7381 * Cortex-A8 erratum workaround:          i960.               (line   39)
   7382 * crash of linker:                       Bug Criteria.       (line    9)
   7383 * CREATE_OBJECT_SYMBOLS:                 Output Section Keywords.
   7384                                                              (line    9)
   7385 * creating a DEF file:                   WIN32.              (line  158)
   7386 * cross reference table:                 Options.            (line  850)
   7387 * cross references:                      Miscellaneous Commands.
   7388                                                              (line   56)
   7389 * current output location:               Location Counter.   (line    6)
   7390 * data:                                  Output Section Data.
   7391                                                              (line    6)
   7392 * DATA_SEGMENT_ALIGN(MAXPAGESIZE, COMMONPAGESIZE): Builtin Functions.
   7393                                                              (line   81)
   7394 * DATA_SEGMENT_END(EXP):                 Builtin Functions.  (line  102)
   7395 * DATA_SEGMENT_RELRO_END(OFFSET, EXP):   Builtin Functions.  (line  108)
   7396 * dbx:                                   Options.            (line 1264)
   7397 * DEF files, creating:                   Options.            (line 1730)
   7398 * default emulation:                     Environment.        (line   21)
   7399 * default input format:                  Environment.        (line    9)
   7400 * DEFINED(SYMBOL):                       Builtin Functions.  (line  119)
   7401 * deleting local symbols:                Options.            (line  587)
   7402 * demangling, default:                   Environment.        (line   29)
   7403 * demangling, from command line:         Options.            (line  891)
   7404 * direct linking to a dll:               WIN32.              (line  239)
   7405 * discarding sections:                   Output Section Discarding.
   7406                                                              (line    6)
   7407 * discontinuous memory:                  MEMORY.             (line    6)
   7408 * DLLs, creating:                        Options.            (line 1632)
   7409 * DLLs, linking to:                      Options.            (line 1761)
   7410 * dot:                                   Location Counter.   (line    6)
   7411 * dot inside sections:                   Location Counter.   (line   36)
   7412 * dot outside sections:                  Location Counter.   (line   66)
   7413 * dynamic linker, from command line:     Options.            (line  904)
   7414 * dynamic symbol table:                  Options.            (line  221)
   7415 * ELF program headers:                   PHDRS.              (line    6)
   7416 * emulation:                             Options.            (line  392)
   7417 * emulation, default:                    Environment.        (line   21)
   7418 * END (MRI):                             MRI.                (line   62)
   7419 * endianness:                            Options.            (line  248)
   7420 * entry point:                           Entry Point.        (line    6)
   7421 * entry point, from command line:        Options.            (line  187)
   7422 * entry point, thumb:                    ARM.                (line   17)
   7423 * ENTRY(SYMBOL):                         Entry Point.        (line    6)
   7424 * error on valid input:                  Bug Criteria.       (line   12)
   7425 * example of linker script:              Simple Example.     (line    6)
   7426 * exporting DLL symbols:                 WIN32.              (line   19)
   7427 * expression evaluation order:           Evaluation.         (line    6)
   7428 * expression sections:                   Expression Section. (line    6)
   7429 * expression, absolute:                  Builtin Functions.  (line   10)
   7430 * expressions:                           Expressions.        (line    6)
   7431 * EXTERN:                                Miscellaneous Commands.
   7432                                                              (line   13)
   7433 * fatal signal:                          Bug Criteria.       (line    9)
   7434 * file name wildcard patterns:           Input Section Wildcards.
   7435                                                              (line    6)
   7436 * FILEHDR:                               PHDRS.              (line   62)
   7437 * filename symbols:                      Output Section Keywords.
   7438                                                              (line    9)
   7439 * fill pattern, entire section:          Output Section Fill.
   7440                                                              (line    6)
   7441 * FILL(EXPRESSION):                      Output Section Data.
   7442                                                              (line   39)
   7443 * finalization function:                 Options.            (line  300)
   7444 * first input file:                      File Commands.      (line   82)
   7445 * first instruction:                     Entry Point.        (line    6)
   7446 * FIX_V4BX:                              ARM.                (line   49)
   7447 * FIX_V4BX_INTERWORKING:                 ARM.                (line   62)
   7448 * FORCE_COMMON_ALLOCATION:               Miscellaneous Commands.
   7449                                                              (line   20)
   7450 * forcing input section alignment:       Forced Input Alignment.
   7451                                                              (line    6)
   7452 * forcing output section alignment:      Forced Output Alignment.
   7453                                                              (line    6)
   7454 * forcing the creation of dynamic sections: Options.         (line  485)
   7455 * FORMAT (MRI):                          MRI.                (line   66)
   7456 * functions in expressions:              Builtin Functions.  (line    6)
   7457 * garbage collection <1>:                Input Section Keep. (line    6)
   7458 * garbage collection:                    Options.            (line  926)
   7459 * generating optimized output:           Options.            (line  466)
   7460 * GNU linker:                            Overview.           (line    6)
   7461 * GNUTARGET:                             Environment.        (line    9)
   7462 * GROUP(FILES):                          File Commands.      (line   47)
   7463 * grouping input files:                  File Commands.      (line   47)
   7464 * groups of archives:                    Options.            (line  696)
   7465 * H8/300 support:                        H8/300.             (line    6)
   7466 * header size:                           Builtin Functions.  (line  182)
   7467 * heap size:                             Options.            (line 1672)
   7468 * help:                                  Options.            (line  957)
   7469 * holes:                                 Location Counter.   (line   12)
   7470 * holes, filling:                        Output Section Data.
   7471                                                              (line   39)
   7472 * HPPA multiple sub-space stubs:         HPPA ELF32.         (line    6)
   7473 * HPPA stub grouping:                    HPPA ELF32.         (line   12)
   7474 * i960 support:                          i960.               (line    6)
   7475 * image base:                            Options.            (line 1679)
   7476 * implicit linker scripts:               Implicit Linker Scripts.
   7477                                                              (line    6)
   7478 * import libraries:                      WIN32.              (line   10)
   7479 * INCLUDE FILENAME:                      File Commands.      (line    9)
   7480 * including a linker script:             File Commands.      (line    9)
   7481 * including an entire archive:           Options.            (line 1449)
   7482 * incremental link:                      Options.            (line  326)
   7483 * INHIBIT_COMMON_ALLOCATION:             Miscellaneous Commands.
   7484                                                              (line   25)
   7485 * initialization function:               Options.            (line  329)
   7486 * initialized data in ROM:               Output Section LMA. (line   39)
   7487 * input file format in linker script:    Format Commands.    (line   35)
   7488 * input filename symbols:                Output Section Keywords.
   7489                                                              (line    9)
   7490 * input files in linker scripts:         File Commands.      (line   19)
   7491 * input files, displaying:               Options.            (line  528)
   7492 * input format:                          Options.            (line  134)
   7493 * input object files in linker scripts:  File Commands.      (line   19)
   7494 * input section alignment:               Forced Input Alignment.
   7495                                                              (line    6)
   7496 * input section basics:                  Input Section Basics.
   7497                                                              (line    6)
   7498 * input section wildcards:               Input Section Wildcards.
   7499                                                              (line    6)
   7500 * input sections:                        Input Section.      (line    6)
   7501 * INPUT(FILES):                          File Commands.      (line   19)
   7502 * INSERT:                                Miscellaneous Commands.
   7503                                                              (line   30)
   7504 * insert user script into default script: Miscellaneous Commands.
   7505                                                              (line   30)
   7506 * integer notation:                      Constants.          (line    6)
   7507 * integer suffixes:                      Constants.          (line   15)
   7508 * internal object-file format:           Canonical format.   (line   11)
   7509 * invalid input:                         Bug Criteria.       (line   14)
   7510 * K and M integer suffixes:              Constants.          (line   15)
   7511 * KEEP:                                  Input Section Keep. (line    6)
   7512 * l =:                                   MEMORY.             (line   74)
   7513 * lazy evaluation:                       Evaluation.         (line    6)
   7514 * ld bugs, reporting:                    Bug Reporting.      (line    6)
   7515 * LDEMULATION:                           Environment.        (line   21)
   7516 * len =:                                 MEMORY.             (line   74)
   7517 * LENGTH =:                              MEMORY.             (line   74)
   7518 * LENGTH(MEMORY):                        Builtin Functions.  (line  136)
   7519 * library search path in linker script:  File Commands.      (line   74)
   7520 * link map:                              Options.            (line  402)
   7521 * link-time runtime library search path: Options.            (line 1151)
   7522 * linker crash:                          Bug Criteria.       (line    9)
   7523 * linker script concepts:                Basic Script Concepts.
   7524                                                              (line    6)
   7525 * linker script example:                 Simple Example.     (line    6)
   7526 * linker script file commands:           File Commands.      (line    6)
   7527 * linker script format:                  Script Format.      (line    6)
   7528 * linker script input object files:      File Commands.      (line   19)
   7529 * linker script simple commands:         Simple Commands.    (line    6)
   7530 * linker scripts:                        Scripts.            (line    6)
   7531 * LIST (MRI):                            MRI.                (line   77)
   7532 * little-endian objects:                 Options.            (line  251)
   7533 * LOAD (MRI):                            MRI.                (line   84)
   7534 * load address:                          Output Section LMA. (line    6)
   7535 * LOADADDR(SECTION):                     Builtin Functions.  (line  139)
   7536 * loading, preventing:                   Output Section Type.
   7537                                                              (line   22)
   7538 * local symbols, deleting:               Options.            (line  591)
   7539 * location counter:                      Location Counter.   (line    6)
   7540 * LONG(EXPRESSION):                      Output Section Data.
   7541                                                              (line    6)
   7542 * M and K integer suffixes:              Constants.          (line   15)
   7543 * M68HC11 and 68HC12 support:            M68HC11/68HC12.     (line    6)
   7544 * machine architecture:                  Miscellaneous Commands.
   7545                                                              (line   72)
   7546 * machine dependencies:                  Machine Dependent.  (line    6)
   7547 * mapping input sections to output sections: Input Section.  (line    6)
   7548 * MAX:                                   Builtin Functions.  (line  142)
   7549 * MAXPAGESIZE:                           Symbolic Constants. (line   10)
   7550 * MEMORY:                                MEMORY.             (line    6)
   7551 * memory region attributes:              MEMORY.             (line   34)
   7552 * memory regions:                        MEMORY.             (line    6)
   7553 * memory regions and sections:           Output Section Region.
   7554                                                              (line    6)
   7555 * memory usage:                          Options.            (line  969)
   7556 * MIN:                                   Builtin Functions.  (line  145)
   7557 * Motorola 68K GOT generation:           M68K.               (line    6)
   7558 * MRI compatibility:                     MRI.                (line    6)
   7559 * MSP430 extra sections:                 MSP430.             (line   11)
   7560 * NAME (MRI):                            MRI.                (line   90)
   7561 * name, section:                         Output Section Name.
   7562                                                              (line    6)
   7563 * names:                                 Symbols.            (line    6)
   7564 * naming the output file:                Options.            (line  460)
   7565 * NEXT(EXP):                             Builtin Functions.  (line  149)
   7566 * NMAGIC:                                Options.            (line  439)
   7567 * NO_ENUM_SIZE_WARNING:                  ARM.                (line  111)
   7568 * NO_WCHAR_SIZE_WARNING:                 ARM.                (line  118)
   7569 * NOCROSSREFS(SECTIONS):                 Miscellaneous Commands.
   7570                                                              (line   56)
   7571 * NOLOAD:                                Output Section Type.
   7572                                                              (line   22)
   7573 * not enough room for program headers:   Builtin Functions.  (line  187)
   7574 * o =:                                   MEMORY.             (line   69)
   7575 * objdump -i:                            BFD.                (line    6)
   7576 * object file management:                BFD.                (line    6)
   7577 * object files:                          Options.            (line   29)
   7578 * object formats available:              BFD.                (line    6)
   7579 * object size:                           Options.            (line  309)
   7580 * OMAGIC:                                Options.            (line  445)
   7581 * ONLY_IF_RO:                            Output Section Constraint.
   7582                                                              (line    6)
   7583 * ONLY_IF_RW:                            Output Section Constraint.
   7584                                                              (line    6)
   7585 * opening object files:                  BFD outline.        (line    6)
   7586 * operators for arithmetic:              Operators.          (line    6)
   7587 * options:                               Options.            (line    6)
   7588 * ORDER (MRI):                           MRI.                (line   95)
   7589 * org =:                                 MEMORY.             (line   69)
   7590 * ORIGIN =:                              MEMORY.             (line   69)
   7591 * ORIGIN(MEMORY):                        Builtin Functions.  (line  155)
   7592 * orphan:                                Orphan Sections.    (line    6)
   7593 * output file after errors:              Options.            (line 1048)
   7594 * output file format in linker script:   Format Commands.    (line   10)
   7595 * output file name in linker script:     File Commands.      (line   64)
   7596 * output section alignment:              Forced Output Alignment.
   7597                                                              (line    6)
   7598 * output section attributes:             Output Section Attributes.
   7599                                                              (line    6)
   7600 * output section data:                   Output Section Data.
   7601                                                              (line    6)
   7602 * OUTPUT(FILENAME):                      File Commands.      (line   64)
   7603 * OUTPUT_ARCH(BFDARCH):                  Miscellaneous Commands.
   7604                                                              (line   72)
   7605 * OUTPUT_FORMAT(BFDNAME):                Format Commands.    (line   10)
   7606 * OVERLAY:                               Overlay Description.
   7607                                                              (line    6)
   7608 * overlays:                              Overlay Description.
   7609                                                              (line    6)
   7610 * partial link:                          Options.            (line  489)
   7611 * PE import table prefixing:             ARM.                (line   23)
   7612 * PHDRS:                                 PHDRS.              (line    6)
   7613 * PIC_VENEER:                            ARM.                (line  124)
   7614 * position independent executables:      Options.            (line 1075)
   7615 * PowerPC ELF32 options:                 PowerPC ELF32.      (line   16)
   7616 * PowerPC GOT:                           PowerPC ELF32.      (line   33)
   7617 * PowerPC long branches:                 PowerPC ELF32.      (line    6)
   7618 * PowerPC PLT:                           PowerPC ELF32.      (line   16)
   7619 * PowerPC stub symbols:                  PowerPC ELF32.      (line   47)
   7620 * PowerPC TLS optimization:              PowerPC ELF32.      (line   51)
   7621 * PowerPC64 dot symbols:                 PowerPC64 ELF64.    (line   33)
   7622 * PowerPC64 ELF64 options:               PowerPC64 ELF64.    (line    6)
   7623 * PowerPC64 multi-TOC:                   PowerPC64 ELF64.    (line   74)
   7624 * PowerPC64 OPD optimization:            PowerPC64 ELF64.    (line   48)
   7625 * PowerPC64 OPD spacing:                 PowerPC64 ELF64.    (line   54)
   7626 * PowerPC64 stub grouping:               PowerPC64 ELF64.    (line    6)
   7627 * PowerPC64 stub symbols:                PowerPC64 ELF64.    (line   29)
   7628 * PowerPC64 TLS optimization:            PowerPC64 ELF64.    (line   43)
   7629 * PowerPC64 TOC optimization:            PowerPC64 ELF64.    (line   60)
   7630 * precedence in expressions:             Operators.          (line    6)
   7631 * prevent unnecessary loading:           Output Section Type.
   7632                                                              (line   22)
   7633 * program headers:                       PHDRS.              (line    6)
   7634 * program headers and sections:          Output Section Phdr.
   7635                                                              (line    6)
   7636 * program headers, not enough room:      Builtin Functions.  (line  187)
   7637 * program segments:                      PHDRS.              (line    6)
   7638 * PROVIDE:                               PROVIDE.            (line    6)
   7639 * PROVIDE_HIDDEN:                        PROVIDE_HIDDEN.     (line    6)
   7640 * PUBLIC (MRI):                          MRI.                (line  103)
   7641 * QUAD(EXPRESSION):                      Output Section Data.
   7642                                                              (line    6)
   7643 * quoted symbol names:                   Symbols.            (line    6)
   7644 * read-only text:                        Options.            (line  439)
   7645 * read/write from cmd line:              Options.            (line  445)
   7646 * region alias:                          REGION_ALIAS.       (line    6)
   7647 * region names:                          REGION_ALIAS.       (line    6)
   7648 * REGION_ALIAS(ALIAS, REGION):           REGION_ALIAS.       (line    6)
   7649 * regions of memory:                     MEMORY.             (line    6)
   7650 * relative expressions:                  Expression Section. (line    6)
   7651 * relaxing addressing modes:             Options.            (line 1089)
   7652 * relaxing on H8/300:                    H8/300.             (line    9)
   7653 * relaxing on i960:                      i960.               (line   31)
   7654 * relaxing on M68HC11:                   M68HC11/68HC12.     (line   12)
   7655 * relaxing on Xtensa:                    Xtensa.             (line   27)
   7656 * relocatable and absolute symbols:      Expression Section. (line    6)
   7657 * relocatable output:                    Options.            (line  489)
   7658 * removing sections:                     Output Section Discarding.
   7659                                                              (line    6)
   7660 * reporting bugs in ld:                  Reporting Bugs.     (line    6)
   7661 * requirements for BFD:                  BFD.                (line   16)
   7662 * retain relocations in final executable: Options.           (line  476)
   7663 * retaining specified symbols:           Options.            (line 1115)
   7664 * ROM initialized data:                  Output Section LMA. (line   39)
   7665 * round up expression:                   Builtin Functions.  (line   38)
   7666 * round up location counter:             Builtin Functions.  (line   38)
   7667 * runtime library name:                  Options.            (line  317)
   7668 * runtime library search path:           Options.            (line 1129)
   7669 * runtime pseudo-relocation:             WIN32.              (line  217)
   7670 * scaled integers:                       Constants.          (line   15)
   7671 * scommon section:                       Input Section Common.
   7672                                                              (line   20)
   7673 * script files:                          Options.            (line  532)
   7674 * scripts:                               Scripts.            (line    6)
   7675 * search directory, from cmd line:       Options.            (line  368)
   7676 * search path in linker script:          File Commands.      (line   74)
   7677 * SEARCH_DIR(PATH):                      File Commands.      (line   74)
   7678 * SECT (MRI):                            MRI.                (line  109)
   7679 * section address:                       Output Section Address.
   7680                                                              (line    6)
   7681 * section address in expression:         Builtin Functions.  (line   17)
   7682 * section alignment:                     Builtin Functions.  (line   63)
   7683 * section alignment, warnings on:        Options.            (line 1427)
   7684 * section data:                          Output Section Data.
   7685                                                              (line    6)
   7686 * section fill pattern:                  Output Section Fill.
   7687                                                              (line    6)
   7688 * section load address:                  Output Section LMA. (line    6)
   7689 * section load address in expression:    Builtin Functions.  (line  139)
   7690 * section name:                          Output Section Name.
   7691                                                              (line    6)
   7692 * section name wildcard patterns:        Input Section Wildcards.
   7693                                                              (line    6)
   7694 * section size:                          Builtin Functions.  (line  166)
   7695 * section, assigning to memory region:   Output Section Region.
   7696                                                              (line    6)
   7697 * section, assigning to program header:  Output Section Phdr.
   7698                                                              (line    6)
   7699 * SECTIONS:                              SECTIONS.           (line    6)
   7700 * sections, discarding:                  Output Section Discarding.
   7701                                                              (line    6)
   7702 * segment origins, cmd line:             Options.            (line 1280)
   7703 * SEGMENT_START(SEGMENT, DEFAULT):       Builtin Functions.  (line  158)
   7704 * segments, ELF:                         PHDRS.              (line    6)
   7705 * shared libraries:                      Options.            (line 1208)
   7706 * SHORT(EXPRESSION):                     Output Section Data.
   7707                                                              (line    6)
   7708 * SIZEOF(SECTION):                       Builtin Functions.  (line  166)
   7709 * SIZEOF_HEADERS:                        Builtin Functions.  (line  182)
   7710 * small common symbols:                  Input Section Common.
   7711                                                              (line   20)
   7712 * SORT:                                  Input Section Wildcards.
   7713                                                              (line   58)
   7714 * SORT_BY_ALIGNMENT:                     Input Section Wildcards.
   7715                                                              (line   54)
   7716 * SORT_BY_NAME:                          Input Section Wildcards.
   7717                                                              (line   46)
   7718 * SPU:                                   SPU ELF.            (line   29)
   7719 * SPU ELF options:                       SPU ELF.            (line    6)
   7720 * SPU extra overlay stubs:               SPU ELF.            (line   19)
   7721 * SPU local store size:                  SPU ELF.            (line   24)
   7722 * SPU overlay stub symbols:              SPU ELF.            (line   15)
   7723 * SPU overlays:                          SPU ELF.            (line    9)
   7724 * SPU plugins:                           SPU ELF.            (line    6)
   7725 * SQUAD(EXPRESSION):                     Output Section Data.
   7726                                                              (line    6)
   7727 * stack size:                            Options.            (line 1919)
   7728 * standard Unix system:                  Options.            (line    7)
   7729 * start of execution:                    Entry Point.        (line    6)
   7730 * STARTUP(FILENAME):                     File Commands.      (line   82)
   7731 * strip all symbols:                     Options.            (line  519)
   7732 * strip debugger symbols:                Options.            (line  523)
   7733 * stripping all but some symbols:        Options.            (line 1115)
   7734 * STUB_GROUP_SIZE:                       ARM.                (line  129)
   7735 * SUBALIGN(SUBSECTION_ALIGN):            Forced Input Alignment.
   7736                                                              (line    6)
   7737 * suffixes for integers:                 Constants.          (line   15)
   7738 * symbol defaults:                       Builtin Functions.  (line  119)
   7739 * symbol definition, scripts:            Assignments.        (line    6)
   7740 * symbol names:                          Symbols.            (line    6)
   7741 * symbol tracing:                        Options.            (line  597)
   7742 * symbol versions:                       VERSION.            (line    6)
   7743 * symbol-only input:                     Options.            (line  508)
   7744 * symbolic constants:                    Symbolic Constants. (line    6)
   7745 * symbols, from command line:            Options.            (line  878)
   7746 * symbols, relocatable and absolute:     Expression Section. (line    6)
   7747 * symbols, retaining selectively:        Options.            (line 1115)
   7748 * synthesizing linker:                   Options.            (line 1089)
   7749 * synthesizing on H8/300:                H8/300.             (line   14)
   7750 * TARGET(BFDNAME):                       Format Commands.    (line   35)
   7751 * TARGET1:                               ARM.                (line   32)
   7752 * TARGET2:                               ARM.                (line   37)
   7753 * text segment origin, cmd line:         Options.            (line 1287)
   7754 * thumb entry point:                     ARM.                (line   17)
   7755 * TI COFF versions:                      TI COFF.            (line    6)
   7756 * traditional format:                    Options.            (line 1259)
   7757 * trampoline generation on M68HC11:      M68HC11/68HC12.     (line   31)
   7758 * trampoline generation on M68HC12:      M68HC11/68HC12.     (line   31)
   7759 * unallocated address, next:             Builtin Functions.  (line  149)
   7760 * undefined symbol:                      Options.            (line  554)
   7761 * undefined symbol in linker script:     Miscellaneous Commands.
   7762                                                              (line   13)
   7763 * undefined symbols, warnings on:        Options.            (line 1423)
   7764 * uninitialized data placement:          Input Section Common.
   7765                                                              (line    6)
   7766 * unspecified memory:                    Output Section Data.
   7767                                                              (line   39)
   7768 * usage:                                 Options.            (line  957)
   7769 * USE_BLX:                               ARM.                (line   74)
   7770 * using a DEF file:                      WIN32.              (line   57)
   7771 * using auto-export functionality:       WIN32.              (line   22)
   7772 * Using decorations:                     WIN32.              (line  162)
   7773 * variables, defining:                   Assignments.        (line    6)
   7774 * verbose:                               Options.            (line 1319)
   7775 * version:                               Options.            (line  581)
   7776 * version script:                        VERSION.            (line    6)
   7777 * version script, symbol versions:       Options.            (line 1325)
   7778 * VERSION {script text}:                 VERSION.            (line    6)
   7779 * versions of symbols:                   VERSION.            (line    6)
   7780 * VFP11_DENORM_FIX:                      ARM.                (line   83)
   7781 * warnings, on combining symbols:        Options.            (line 1336)
   7782 * warnings, on section alignment:        Options.            (line 1427)
   7783 * warnings, on undefined symbols:        Options.            (line 1423)
   7784 * weak externals:                        WIN32.              (line  407)
   7785 * what is this?:                         Overview.           (line    6)
   7786 * wildcard file name patterns:           Input Section Wildcards.
   7787                                                              (line    6)
   7788 * Xtensa options:                        Xtensa.             (line   56)
   7789 * Xtensa processors:                     Xtensa.             (line    6)
   7790 
   7791 
   7792 
   7793 Tag Table:
   7794 Node: Top871
   7795 Node: Overview1654
   7796 Node: Invocation2768
   7797 Node: Options3176
   7798 Node: Environment93392
   7799 Node: Scripts95152
   7800 Node: Basic Script Concepts96886
   7801 Node: Script Format99593
   7802 Node: Simple Example100456
   7803 Node: Simple Commands103552
   7804 Node: Entry Point104058
   7805 Node: File Commands104991
   7806 Node: Format Commands108992
   7807 Node: REGION_ALIAS110948
   7808 Node: Miscellaneous Commands115780
   7809 Node: Assignments119156
   7810 Node: Simple Assignments119647
   7811 Node: PROVIDE121383
   7812 Node: PROVIDE_HIDDEN122588
   7813 Node: Source Code Reference122832
   7814 Node: SECTIONS126412
   7815 Node: Output Section Description128303
   7816 Node: Output Section Name129390
   7817 Node: Output Section Address130266
   7818 Node: Input Section132501
   7819 Node: Input Section Basics133302
   7820 Node: Input Section Wildcards136520
   7821 Node: Input Section Common141253
   7822 Node: Input Section Keep142735
   7823 Node: Input Section Example143225
   7824 Node: Output Section Data144193
   7825 Node: Output Section Keywords146970
   7826 Node: Output Section Discarding150539
   7827 Node: Output Section Attributes151720
   7828 Node: Output Section Type152821
   7829 Node: Output Section LMA153892
   7830 Node: Forced Output Alignment156963
   7831 Node: Forced Input Alignment157231
   7832 Node: Output Section Constraint157620
   7833 Node: Output Section Region158048
   7834 Node: Output Section Phdr158481
   7835 Node: Output Section Fill159145
   7836 Node: Overlay Description160287
   7837 Node: MEMORY164589
   7838 Node: PHDRS168923
   7839 Node: VERSION174177
   7840 Node: Expressions182270
   7841 Node: Constants183199
   7842 Node: Symbolic Constants184074
   7843 Node: Symbols184625
   7844 Node: Orphan Sections185372
   7845 Node: Location Counter186536
   7846 Node: Operators190972
   7847 Node: Evaluation191894
   7848 Node: Expression Section193258
   7849 Node: Builtin Functions196859
   7850 Node: Implicit Linker Scripts204815
   7851 Node: Machine Dependent205590
   7852 Node: H8/300206606
   7853 Node: i960208231
   7854 Node: M68HC11/68HC12210435
   7855 Node: ARM211889
   7856 Node: HPPA ELF32219401
   7857 Node: M68K221024
   7858 Node: MMIX221933
   7859 Node: MSP430223098
   7860 Node: PowerPC ELF32224147
   7861 Node: PowerPC64 ELF64226983
   7862 Node: SPU ELF231399
   7863 Node: TI COFF234031
   7864 Node: WIN32234557
   7865 Node: Xtensa254682
   7866 Node: BFD257647
   7867 Node: BFD outline259102
   7868 Node: BFD information loss260388
   7869 Node: Canonical format262905
   7870 Node: Reporting Bugs267262
   7871 Node: Bug Criteria267956
   7872 Node: Bug Reporting268655
   7873 Node: MRI275694
   7874 Node: GNU Free Documentation License280337
   7875 Node: LD Index305493
   7876 
   7877 End Tag Table
   7878