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      1 //  2016 and later: Unicode, Inc. and others.
      2 // License & terms of use: http://www.unicode.org/copyright.html
      3 /*
      4 ******************************************************************************
      5 *
      6 *   Copyright (C) 1997-2016, International Business Machines
      7 *   Corporation and others.  All Rights Reserved.
      8 *
      9 ******************************************************************************
     10 *
     11 *  FILE NAME : platform.h
     12 *
     13 *   Date        Name        Description
     14 *   05/13/98    nos         Creation (content moved here from ptypes.h).
     15 *   03/02/99    stephen     Added AS400 support.
     16 *   03/30/99    stephen     Added Linux support.
     17 *   04/13/99    stephen     Reworked for autoconf.
     18 ******************************************************************************
     19 */
     20 
     21 #ifndef _PLATFORM_H
     22 #define _PLATFORM_H
     23 
     24 #include "unicode/uconfig.h"
     25 #include "unicode/uvernum.h"
     26 
     27 /**
     28  * \file
     29  * \brief Basic types for the platform.
     30  *
     31  * This file used to be generated by autoconf/configure.
     32  * Starting with ICU 49, platform.h is a normal source file,
     33  * to simplify cross-compiling and working with non-autoconf/make build systems.
     34  *
     35  * When a value in this file does not work on a platform, then please
     36  * try to derive it from the U_PLATFORM value
     37  * (for which we might need a new value constant in rare cases)
     38  * and/or from other macros that are predefined by the compiler
     39  * or defined in standard (POSIX or platform or compiler) headers.
     40  *
     41  * As a temporary workaround, you can add an explicit <code>#define</code> for some macros
     42  * before it is first tested, or add an equivalent -D macro definition
     43  * to the compiler's command line.
     44  *
     45  * Note: Some compilers provide ways to show the predefined macros.
     46  * For example, with gcc you can compile an empty .c file and have the compiler
     47  * print the predefined macros with
     48  * \code
     49  * gcc -E -dM -x c /dev/null | sort
     50  * \endcode
     51  * (You can provide an actual empty .c file rather than /dev/null.
     52  * <code>-x c++</code> is for C++.)
     53  */
     54 
     55 /**
     56  * Define some things so that they can be documented.
     57  * @internal
     58  */
     59 #ifdef U_IN_DOXYGEN
     60 /*
     61  * Problem: "platform.h:335: warning: documentation for unknown define U_HAVE_STD_STRING found." means that U_HAVE_STD_STRING is not documented.
     62  * Solution: #define any defines for non @internal API here, so that they are visible in the docs.  If you just set PREDEFINED in Doxyfile.in,  they won't be documented.
     63  */
     64 
     65 /* None for now. */
     66 #endif
     67 
     68 /**
     69  * \def U_PLATFORM
     70  * The U_PLATFORM macro defines the platform we're on.
     71  *
     72  * We used to define one different, value-less macro per platform.
     73  * That made it hard to know the set of relevant platforms and macros,
     74  * and hard to deal with variants of platforms.
     75  *
     76  * Starting with ICU 49, we define platforms as numeric macros,
     77  * with ranges of values for related platforms and their variants.
     78  * The U_PLATFORM macro is set to one of these values.
     79  *
     80  * Historical note from the Solaris Wikipedia article:
     81  * AT&T and Sun collaborated on a project to merge the most popular Unix variants
     82  * on the market at that time: BSD, System V, and Xenix.
     83  * This became Unix System V Release 4 (SVR4).
     84  *
     85  * @internal
     86  */
     87 
     88 /** Unknown platform. @internal */
     89 #define U_PF_UNKNOWN 0
     90 /** Windows @internal */
     91 #define U_PF_WINDOWS 1000
     92 /** MinGW. Windows, calls to Win32 API, but using GNU gcc and binutils. @internal */
     93 #define U_PF_MINGW 1800
     94 /**
     95  * Cygwin. Windows, calls to cygwin1.dll for Posix functions,
     96  * using MSVC or GNU gcc and binutils.
     97  * @internal
     98  */
     99 #define U_PF_CYGWIN 1900
    100 /* Reserve 2000 for U_PF_UNIX? */
    101 /** HP-UX is based on UNIX System V. @internal */
    102 #define U_PF_HPUX 2100
    103 /** Solaris is a Unix operating system based on SVR4. @internal */
    104 #define U_PF_SOLARIS 2600
    105 /** BSD is a UNIX operating system derivative. @internal */
    106 #define U_PF_BSD 3000
    107 /** AIX is based on UNIX System V Releases and 4.3 BSD. @internal */
    108 #define U_PF_AIX 3100
    109 /** IRIX is based on UNIX System V with BSD extensions. @internal */
    110 #define U_PF_IRIX 3200
    111 /**
    112  * Darwin is a POSIX-compliant operating system, composed of code developed by Apple,
    113  * as well as code derived from NeXTSTEP, BSD, and other projects,
    114  * built around the Mach kernel.
    115  * Darwin forms the core set of components upon which Mac OS X, Apple TV, and iOS are based.
    116  * (Original description modified from WikiPedia.)
    117  * @internal
    118  */
    119 #define U_PF_DARWIN 3500
    120 /** iPhone OS (iOS) is a derivative of Mac OS X. @internal */
    121 #define U_PF_IPHONE 3550
    122 /** QNX is a commercial Unix-like real-time operating system related to BSD. @internal */
    123 #define U_PF_QNX 3700
    124 /** Linux is a Unix-like operating system. @internal */
    125 #define U_PF_LINUX 4000
    126 /**
    127  * Native Client is pretty close to Linux.
    128  * See https://developer.chrome.com/native-client and
    129  *  http://www.chromium.org/nativeclient
    130  *  @internal
    131  */
    132 #define U_PF_BROWSER_NATIVE_CLIENT 4020
    133 /** Android is based on Linux. @internal */
    134 #define U_PF_ANDROID 4050
    135 /** Fuchsia is a POSIX-ish platform. @internal */
    136 #define U_PF_FUCHSIA 4100
    137 /* Maximum value for Linux-based platform is 4499 */
    138 /** z/OS is the successor to OS/390 which was the successor to MVS. @internal */
    139 #define U_PF_OS390 9000
    140 /** "IBM i" is the current name of what used to be i5/OS and earlier OS/400. @internal */
    141 #define U_PF_OS400 9400
    142 
    143 #ifdef U_PLATFORM
    144     /* Use the predefined value. */
    145 #elif defined(__MINGW32__)
    146 #   define U_PLATFORM U_PF_MINGW
    147 #elif defined(__CYGWIN__)
    148 #   define U_PLATFORM U_PF_CYGWIN
    149 #elif defined(WIN32) || defined(_WIN32) || defined(WIN64) || defined(_WIN64)
    150 #   define U_PLATFORM U_PF_WINDOWS
    151 #elif defined(__ANDROID__)
    152 #   define U_PLATFORM U_PF_ANDROID
    153     /* Android wchar_t support depends on the API level. */
    154 #   include <android/api-level.h>
    155 #elif defined(__pnacl__) || defined(__native_client__)
    156 #   define U_PLATFORM U_PF_BROWSER_NATIVE_CLIENT
    157 #elif defined(__Fuchsia__)
    158 #   define U_PLATFORM U_PF_FUCHSIA
    159 #elif defined(linux) || defined(__linux__) || defined(__linux)
    160 #   define U_PLATFORM U_PF_LINUX
    161 #elif defined(__APPLE__) && defined(__MACH__)
    162 #   include <TargetConditionals.h>
    163 #   if defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE  /* variant of TARGET_OS_MAC */
    164 #       define U_PLATFORM U_PF_IPHONE
    165 #   else
    166 #       define U_PLATFORM U_PF_DARWIN
    167 #   endif
    168 #elif defined(BSD) || defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__NetBSD__) || defined(__OpenBSD__) || defined(__MirBSD__)
    169 #   if defined(__FreeBSD__)
    170 #       include <sys/endian.h>
    171 #   endif
    172 #   define U_PLATFORM U_PF_BSD
    173 #elif defined(sun) || defined(__sun)
    174     /* Check defined(__SVR4) || defined(__svr4__) to distinguish Solaris from SunOS? */
    175 #   define U_PLATFORM U_PF_SOLARIS
    176 #   if defined(__GNUC__)
    177         /* Solaris/GCC needs this header file to get the proper endianness. Normally, this
    178          * header file is included with stddef.h but on Solairs/GCC, the GCC version of stddef.h
    179          *  is included which does not include this header file.
    180          */
    181 #       include <sys/isa_defs.h>
    182 #   endif
    183 #elif defined(_AIX) || defined(__TOS_AIX__)
    184 #   define U_PLATFORM U_PF_AIX
    185 #elif defined(_hpux) || defined(hpux) || defined(__hpux)
    186 #   define U_PLATFORM U_PF_HPUX
    187 #elif defined(sgi) || defined(__sgi)
    188 #   define U_PLATFORM U_PF_IRIX
    189 #elif defined(__QNX__) || defined(__QNXNTO__)
    190 #   define U_PLATFORM U_PF_QNX
    191 #elif defined(__TOS_MVS__)
    192 #   define U_PLATFORM U_PF_OS390
    193 #elif defined(__OS400__) || defined(__TOS_OS400__)
    194 #   define U_PLATFORM U_PF_OS400
    195 #else
    196 #   define U_PLATFORM U_PF_UNKNOWN
    197 #endif
    198 
    199 /**
    200  * \def UPRV_INCOMPLETE_CPP11_SUPPORT
    201  * This switch turns off ICU 60 NumberFormatter code.
    202  * By default, this switch is enabled on AIX and z/OS,
    203  * which have poor C++11 support.
    204  *
    205  * NOTE: This switch is intended to be temporary; see #13393.
    206  *
    207  * @internal
    208  */
    209 #ifndef UPRV_INCOMPLETE_CPP11_SUPPORT
    210 #   define UPRV_INCOMPLETE_CPP11_SUPPORT (U_PLATFORM == U_PF_AIX || U_PLATFORM == U_PF_OS390 || U_PLATFORM == U_PF_SOLARIS )
    211 #endif
    212 
    213 /**
    214  * \def CYGWINMSVC
    215  * Defined if this is Windows with Cygwin, but using MSVC rather than gcc.
    216  * Otherwise undefined.
    217  * @internal
    218  */
    219 /* Commented out because this is already set in mh-cygwin-msvc
    220 #if U_PLATFORM == U_PF_CYGWIN && defined(_MSC_VER)
    221 #   define CYGWINMSVC
    222 #endif
    223 */
    224 
    225 /**
    226  * \def U_PLATFORM_USES_ONLY_WIN32_API
    227  * Defines whether the platform uses only the Win32 API.
    228  * Set to 1 for Windows/MSVC and MinGW but not Cygwin.
    229  * @internal
    230  */
    231 #ifdef U_PLATFORM_USES_ONLY_WIN32_API
    232     /* Use the predefined value. */
    233 #elif (U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_MINGW) || defined(CYGWINMSVC)
    234 #   define U_PLATFORM_USES_ONLY_WIN32_API 1
    235 #else
    236     /* Cygwin implements POSIX. */
    237 #   define U_PLATFORM_USES_ONLY_WIN32_API 0
    238 #endif
    239 
    240 /**
    241  * \def U_PLATFORM_HAS_WIN32_API
    242  * Defines whether the Win32 API is available on the platform.
    243  * Set to 1 for Windows/MSVC, MinGW and Cygwin.
    244  * @internal
    245  */
    246 #ifdef U_PLATFORM_HAS_WIN32_API
    247     /* Use the predefined value. */
    248 #elif U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN
    249 #   define U_PLATFORM_HAS_WIN32_API 1
    250 #else
    251 #   define U_PLATFORM_HAS_WIN32_API 0
    252 #endif
    253 
    254 /**
    255  * \def U_PLATFORM_HAS_WINUWP_API
    256  * Defines whether target is intended for Universal Windows Platform API
    257  * Set to 1 for Windows10 Release Solution Configuration
    258  * @internal
    259  */
    260 #ifdef U_PLATFORM_HAS_WINUWP_API
    261     /* Use the predefined value. */
    262 #else
    263 #   define U_PLATFORM_HAS_WINUWP_API 0
    264 #endif
    265 
    266 /**
    267  * \def U_PLATFORM_IMPLEMENTS_POSIX
    268  * Defines whether the platform implements (most of) the POSIX API.
    269  * Set to 1 for Cygwin and most other platforms.
    270  * @internal
    271  */
    272 #ifdef U_PLATFORM_IMPLEMENTS_POSIX
    273     /* Use the predefined value. */
    274 #elif U_PLATFORM_USES_ONLY_WIN32_API
    275 #   define U_PLATFORM_IMPLEMENTS_POSIX 0
    276 #else
    277 #   define U_PLATFORM_IMPLEMENTS_POSIX 1
    278 #endif
    279 
    280 /**
    281  * \def U_PLATFORM_IS_LINUX_BASED
    282  * Defines whether the platform is Linux or one of its derivatives.
    283  * @internal
    284  */
    285 #ifdef U_PLATFORM_IS_LINUX_BASED
    286     /* Use the predefined value. */
    287 #elif U_PF_LINUX <= U_PLATFORM && U_PLATFORM <= 4499
    288 #   define U_PLATFORM_IS_LINUX_BASED 1
    289 #else
    290 #   define U_PLATFORM_IS_LINUX_BASED 0
    291 #endif
    292 
    293 /**
    294  * \def U_PLATFORM_IS_DARWIN_BASED
    295  * Defines whether the platform is Darwin or one of its derivatives.
    296  * @internal
    297  */
    298 #ifdef U_PLATFORM_IS_DARWIN_BASED
    299     /* Use the predefined value. */
    300 #elif U_PF_DARWIN <= U_PLATFORM && U_PLATFORM <= U_PF_IPHONE
    301 #   define U_PLATFORM_IS_DARWIN_BASED 1
    302 #else
    303 #   define U_PLATFORM_IS_DARWIN_BASED 0
    304 #endif
    305 
    306 /**
    307  * \def U_HAVE_STDINT_H
    308  * Defines whether stdint.h is available. It is a C99 standard header.
    309  * We used to include inttypes.h which includes stdint.h but we usually do not need
    310  * the additional definitions from inttypes.h.
    311  * @internal
    312  */
    313 #ifdef U_HAVE_STDINT_H
    314     /* Use the predefined value. */
    315 #elif U_PLATFORM_USES_ONLY_WIN32_API
    316 #   if defined(__BORLANDC__) || U_PLATFORM == U_PF_MINGW || (defined(_MSC_VER) && _MSC_VER>=1600)
    317         /* Windows Visual Studio 9 and below do not have stdint.h & inttypes.h, but VS 2010 adds them. */
    318 #       define U_HAVE_STDINT_H 1
    319 #   else
    320 #       define U_HAVE_STDINT_H 0
    321 #   endif
    322 #elif U_PLATFORM == U_PF_SOLARIS
    323     /* Solaris has inttypes.h but not stdint.h. */
    324 #   define U_HAVE_STDINT_H 0
    325 #elif U_PLATFORM == U_PF_AIX && !defined(_AIX51) && defined(_POWER)
    326     /* PPC AIX <= 4.3 has inttypes.h but not stdint.h. */
    327 #   define U_HAVE_STDINT_H 0
    328 #else
    329 #   define U_HAVE_STDINT_H 1
    330 #endif
    331 
    332 /**
    333  * \def U_HAVE_INTTYPES_H
    334  * Defines whether inttypes.h is available. It is a C99 standard header.
    335  * We include inttypes.h where it is available but stdint.h is not.
    336  * @internal
    337  */
    338 #ifdef U_HAVE_INTTYPES_H
    339     /* Use the predefined value. */
    340 #elif U_PLATFORM == U_PF_SOLARIS
    341     /* Solaris has inttypes.h but not stdint.h. */
    342 #   define U_HAVE_INTTYPES_H 1
    343 #elif U_PLATFORM == U_PF_AIX && !defined(_AIX51) && defined(_POWER)
    344     /* PPC AIX <= 4.3 has inttypes.h but not stdint.h. */
    345 #   define U_HAVE_INTTYPES_H 1
    346 #else
    347     /* Most platforms have both inttypes.h and stdint.h, or neither. */
    348 #   define U_HAVE_INTTYPES_H U_HAVE_STDINT_H
    349 #endif
    350 
    351 /*===========================================================================*/
    352 /** @{ Compiler and environment features                                     */
    353 /*===========================================================================*/
    354 
    355 /**
    356  * \def U_GCC_MAJOR_MINOR
    357  * Indicates whether the compiler is gcc (test for != 0),
    358  * and if so, contains its major (times 100) and minor version numbers.
    359  * If the compiler is not gcc, then U_GCC_MAJOR_MINOR == 0.
    360  *
    361  * For example, for testing for whether we have gcc, and whether it's 4.6 or higher,
    362  * use "#if U_GCC_MAJOR_MINOR >= 406".
    363  * @internal
    364  */
    365 #ifdef __GNUC__
    366 #   define U_GCC_MAJOR_MINOR (__GNUC__ * 100 + __GNUC_MINOR__)
    367 #else
    368 #   define U_GCC_MAJOR_MINOR 0
    369 #endif
    370 
    371 /**
    372  * \def U_IS_BIG_ENDIAN
    373  * Determines the endianness of the platform.
    374  * @internal
    375  */
    376 #ifdef U_IS_BIG_ENDIAN
    377     /* Use the predefined value. */
    378 #elif defined(BYTE_ORDER) && defined(BIG_ENDIAN)
    379 #   define U_IS_BIG_ENDIAN (BYTE_ORDER == BIG_ENDIAN)
    380 #elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__)
    381     /* gcc */
    382 #   define U_IS_BIG_ENDIAN (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
    383 #elif defined(__BIG_ENDIAN__) || defined(_BIG_ENDIAN)
    384 #   define U_IS_BIG_ENDIAN 1
    385 #elif defined(__LITTLE_ENDIAN__) || defined(_LITTLE_ENDIAN)
    386 #   define U_IS_BIG_ENDIAN 0
    387 #elif U_PLATFORM == U_PF_OS390 || U_PLATFORM == U_PF_OS400 || defined(__s390__) || defined(__s390x__)
    388     /* These platforms do not appear to predefine any endianness macros. */
    389 #   define U_IS_BIG_ENDIAN 1
    390 #elif defined(_PA_RISC1_0) || defined(_PA_RISC1_1) || defined(_PA_RISC2_0)
    391     /* HPPA do not appear to predefine any endianness macros. */
    392 #   define U_IS_BIG_ENDIAN 1
    393 #elif defined(sparc) || defined(__sparc) || defined(__sparc__)
    394     /* Some sparc based systems (e.g. Linux) do not predefine any endianness macros. */
    395 #   define U_IS_BIG_ENDIAN 1
    396 #else
    397 #   define U_IS_BIG_ENDIAN 0
    398 #endif
    399 
    400 /**
    401  * \def U_HAVE_PLACEMENT_NEW
    402  * Determines whether to override placement new and delete for STL.
    403  * @stable ICU 2.6
    404  */
    405 #ifdef U_HAVE_PLACEMENT_NEW
    406     /* Use the predefined value. */
    407 #elif defined(__BORLANDC__)
    408 #   define U_HAVE_PLACEMENT_NEW 0
    409 #else
    410 #   define U_HAVE_PLACEMENT_NEW 1
    411 #endif
    412 
    413 /**
    414  * \def U_HAVE_DEBUG_LOCATION_NEW
    415  * Define this to define the MFC debug version of the operator new.
    416  *
    417  * @stable ICU 3.4
    418  */
    419 #ifdef U_HAVE_DEBUG_LOCATION_NEW
    420     /* Use the predefined value. */
    421 #elif defined(_MSC_VER)
    422 #   define U_HAVE_DEBUG_LOCATION_NEW 1
    423 #else
    424 #   define U_HAVE_DEBUG_LOCATION_NEW 0
    425 #endif
    426 
    427 /* Compatibility with compilers other than clang: http://clang.llvm.org/docs/LanguageExtensions.html */
    428 #ifndef __has_attribute
    429 #    define __has_attribute(x) 0
    430 #endif
    431 #ifndef __has_cpp_attribute
    432 #    define __has_cpp_attribute(x) 0
    433 #endif
    434 #ifndef __has_builtin
    435 #    define __has_builtin(x) 0
    436 #endif
    437 #ifndef __has_feature
    438 #    define __has_feature(x) 0
    439 #endif
    440 #ifndef __has_extension
    441 #    define __has_extension(x) 0
    442 #endif
    443 #ifndef __has_warning
    444 #    define __has_warning(x) 0
    445 #endif
    446 
    447 /**
    448  * \def U_MALLOC_ATTR
    449  * Attribute to mark functions as malloc-like
    450  * @internal
    451  */
    452 #if defined(__GNUC__) && __GNUC__>=3
    453 #    define U_MALLOC_ATTR __attribute__ ((__malloc__))
    454 #else
    455 #    define U_MALLOC_ATTR
    456 #endif
    457 
    458 /**
    459  * \def U_ALLOC_SIZE_ATTR
    460  * Attribute to specify the size of the allocated buffer for malloc-like functions
    461  * @internal
    462  */
    463 #if (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))) || __has_attribute(alloc_size)
    464 #   define U_ALLOC_SIZE_ATTR(X) __attribute__ ((alloc_size(X)))
    465 #   define U_ALLOC_SIZE_ATTR2(X,Y) __attribute__ ((alloc_size(X,Y)))
    466 #else
    467 #   define U_ALLOC_SIZE_ATTR(X)
    468 #   define U_ALLOC_SIZE_ATTR2(X,Y)
    469 #endif
    470 
    471 /**
    472  * \def U_CPLUSPLUS_VERSION
    473  * 0 if no C++; 1, 11, 14, ... if C++.
    474  * Support for specific features cannot always be determined by the C++ version alone.
    475  * @internal
    476  */
    477 #ifdef U_CPLUSPLUS_VERSION
    478 #   if U_CPLUSPLUS_VERSION != 0 && !defined(__cplusplus)
    479 #       undef U_CPLUSPLUS_VERSION
    480 #       define U_CPLUSPLUS_VERSION 0
    481 #   endif
    482     /* Otherwise use the predefined value. */
    483 #elif !defined(__cplusplus)
    484 #   define U_CPLUSPLUS_VERSION 0
    485 #elif __cplusplus >= 201402L
    486 #   define U_CPLUSPLUS_VERSION 14
    487 #elif __cplusplus >= 201103L
    488 #   define U_CPLUSPLUS_VERSION 11
    489 #else
    490     // C++98 or C++03
    491 #   define U_CPLUSPLUS_VERSION 1
    492 #endif
    493 
    494 #if (U_PLATFORM == U_PF_AIX || U_PLATFORM == U_PF_OS390) && defined(__cplusplus) &&(U_CPLUSPLUS_VERSION < 11)
    495 // add in std::nullptr_t
    496 namespace std {
    497   typedef decltype(nullptr) nullptr_t;
    498 };
    499 #endif
    500 
    501 /**
    502  * \def U_NOEXCEPT
    503  * "noexcept" if supported, otherwise empty.
    504  * Some code, especially STL containers, uses move semantics of objects only
    505  * if the move constructor and the move operator are declared as not throwing exceptions.
    506  * @internal
    507  */
    508 #ifdef U_NOEXCEPT
    509     /* Use the predefined value. */
    510 #elif defined(_HAS_EXCEPTIONS) && !_HAS_EXCEPTIONS  /* Visual Studio */
    511 #   define U_NOEXCEPT
    512 #elif U_CPLUSPLUS_VERSION >= 11 || __has_feature(cxx_noexcept) || __has_extension(cxx_noexcept) \
    513         || (defined(_MSC_VER) && _MSC_VER >= 1900)  /* Visual Studio 2015 */
    514 #   define U_NOEXCEPT noexcept
    515 #else
    516 #   define U_NOEXCEPT
    517 #endif
    518 
    519 /**
    520  * \def U_FALLTHROUGH
    521  * Annotate intentional fall-through between switch labels.
    522  * http://clang.llvm.org/docs/AttributeReference.html#fallthrough-clang-fallthrough
    523  * @internal
    524  */
    525 #ifndef __cplusplus
    526     // Not for C.
    527 #elif defined(U_FALLTHROUGH)
    528     // Use the predefined value.
    529 #elif defined(__clang__)
    530     // Test for compiler vs. feature separately.
    531     // Other compilers might choke on the feature test.
    532 #   if __has_cpp_attribute(clang::fallthrough) || \
    533             (__has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough"))
    534 #       define U_FALLTHROUGH [[clang::fallthrough]]
    535 #   endif
    536 #endif
    537 
    538 #ifndef U_FALLTHROUGH
    539 #   define U_FALLTHROUGH
    540 #endif
    541 
    542 /** @} */
    543 
    544 /*===========================================================================*/
    545 /** @{ Character data types                                                  */
    546 /*===========================================================================*/
    547 
    548 /**
    549  * U_CHARSET_FAMILY is equal to this value when the platform is an ASCII based platform.
    550  * @stable ICU 2.0
    551  */
    552 #define U_ASCII_FAMILY 0
    553 
    554 /**
    555  * U_CHARSET_FAMILY is equal to this value when the platform is an EBCDIC based platform.
    556  * @stable ICU 2.0
    557  */
    558 #define U_EBCDIC_FAMILY 1
    559 
    560 /**
    561  * \def U_CHARSET_FAMILY
    562  *
    563  * <p>These definitions allow to specify the encoding of text
    564  * in the char data type as defined by the platform and the compiler.
    565  * It is enough to determine the code point values of "invariant characters",
    566  * which are the ones shared by all encodings that are in use
    567  * on a given platform.</p>
    568  *
    569  * <p>Those "invariant characters" should be all the uppercase and lowercase
    570  * latin letters, the digits, the space, and "basic punctuation".
    571  * Also, '\\n', '\\r', '\\t' should be available.</p>
    572  *
    573  * <p>The list of "invariant characters" is:<br>
    574  * \code
    575  *    A-Z  a-z  0-9  SPACE  "  %  &amp;  '  (  )  *  +  ,  -  .  /  :  ;  <  =  >  ?  _
    576  * \endcode
    577  * <br>
    578  * (52 letters + 10 numbers + 20 punc/sym/space = 82 total)</p>
    579  *
    580  * <p>This matches the IBM Syntactic Character Set (CS 640).</p>
    581  *
    582  * <p>In other words, all the graphic characters in 7-bit ASCII should
    583  * be safely accessible except the following:</p>
    584  *
    585  * \code
    586  *    '\' <backslash>
    587  *    '[' <left bracket>
    588  *    ']' <right bracket>
    589  *    '{' <left brace>
    590  *    '}' <right brace>
    591  *    '^' <circumflex>
    592  *    '~' <tilde>
    593  *    '!' <exclamation mark>
    594  *    '#' <number sign>
    595  *    '|' <vertical line>
    596  *    '$' <dollar sign>
    597  *    '@' <commercial at>
    598  *    '`' <grave accent>
    599  * \endcode
    600  * @stable ICU 2.0
    601  */
    602 #ifdef U_CHARSET_FAMILY
    603     /* Use the predefined value. */
    604 #elif U_PLATFORM == U_PF_OS390 && (!defined(__CHARSET_LIB) || !__CHARSET_LIB)
    605 #   define U_CHARSET_FAMILY U_EBCDIC_FAMILY
    606 #elif U_PLATFORM == U_PF_OS400 && !defined(__UTF32__)
    607 #   define U_CHARSET_FAMILY U_EBCDIC_FAMILY
    608 #else
    609 #   define U_CHARSET_FAMILY U_ASCII_FAMILY
    610 #endif
    611 
    612 /**
    613  * \def U_CHARSET_IS_UTF8
    614  *
    615  * Hardcode the default charset to UTF-8.
    616  *
    617  * If this is set to 1, then
    618  * - ICU will assume that all non-invariant char*, StringPiece, std::string etc.
    619  *   contain UTF-8 text, regardless of what the system API uses
    620  * - some ICU code will use fast functions like u_strFromUTF8()
    621  *   rather than the more general and more heavy-weight conversion API (ucnv.h)
    622  * - ucnv_getDefaultName() always returns "UTF-8"
    623  * - ucnv_setDefaultName() is disabled and will not change the default charset
    624  * - static builds of ICU are smaller
    625  * - more functionality is available with the UCONFIG_NO_CONVERSION build-time
    626  *   configuration option (see unicode/uconfig.h)
    627  * - the UCONFIG_NO_CONVERSION build option in uconfig.h is more usable
    628  *
    629  * @stable ICU 4.2
    630  * @see UCONFIG_NO_CONVERSION
    631  */
    632 #ifdef U_CHARSET_IS_UTF8
    633     /* Use the predefined value. */
    634 #elif U_PLATFORM == U_PF_ANDROID || U_PLATFORM_IS_DARWIN_BASED
    635 #   define U_CHARSET_IS_UTF8 1
    636 #elif U_PLATFORM_IS_LINUX_BASED
    637    /*
    638     * Google-specific: Set to 1 to match the google3 execution environment's
    639     * use of UTF-8, on both Linux server and workstation machines.
    640     */
    641 #   define U_CHARSET_IS_UTF8 1
    642 #else
    643 #   define U_CHARSET_IS_UTF8 0
    644 #endif
    645 
    646 /** @} */
    647 
    648 /*===========================================================================*/
    649 /** @{ Information about wchar support                                       */
    650 /*===========================================================================*/
    651 
    652 /**
    653  * \def U_HAVE_WCHAR_H
    654  * Indicates whether <wchar.h> is available (1) or not (0). Set to 1 by default.
    655  *
    656  * @stable ICU 2.0
    657  */
    658 #ifdef U_HAVE_WCHAR_H
    659     /* Use the predefined value. */
    660 #elif U_PLATFORM == U_PF_ANDROID && __ANDROID_API__ < 9
    661     /*
    662      * Android before Gingerbread (Android 2.3, API level 9) did not support wchar_t.
    663      * The type and header existed, but the library functions did not work as expected.
    664      * The size of wchar_t was 1 but L"xyz" string literals had 32-bit units anyway.
    665      */
    666 #   define U_HAVE_WCHAR_H 0
    667 #else
    668 #   define U_HAVE_WCHAR_H 1
    669 #endif
    670 
    671 /**
    672  * \def U_SIZEOF_WCHAR_T
    673  * U_SIZEOF_WCHAR_T==sizeof(wchar_t)
    674  *
    675  * @stable ICU 2.0
    676  */
    677 #ifdef U_SIZEOF_WCHAR_T
    678     /* Use the predefined value. */
    679 #elif (U_PLATFORM == U_PF_ANDROID && __ANDROID_API__ < 9)
    680     /*
    681      * Classic Mac OS and Mac OS X before 10.3 (Panther) did not support wchar_t or wstring.
    682      * Newer Mac OS X has size 4.
    683      */
    684 #   define U_SIZEOF_WCHAR_T 1
    685 #elif U_PLATFORM_HAS_WIN32_API || U_PLATFORM == U_PF_CYGWIN
    686 #   define U_SIZEOF_WCHAR_T 2
    687 #elif U_PLATFORM == U_PF_AIX
    688     /*
    689      * AIX 6.1 information, section "Wide character data representation":
    690      * "... the wchar_t datatype is 32-bit in the 64-bit environment and
    691      * 16-bit in the 32-bit environment."
    692      * and
    693      * "All locales use Unicode for their wide character code values (process code),
    694      * except the IBM-eucTW codeset."
    695      */
    696 #   ifdef __64BIT__
    697 #       define U_SIZEOF_WCHAR_T 4
    698 #   else
    699 #       define U_SIZEOF_WCHAR_T 2
    700 #   endif
    701 #elif U_PLATFORM == U_PF_OS390
    702     /*
    703      * z/OS V1R11 information center, section "LP64 | ILP32":
    704      * "In 31-bit mode, the size of long and pointers is 4 bytes and the size of wchar_t is 2 bytes.
    705      * Under LP64, the size of long and pointer is 8 bytes and the size of wchar_t is 4 bytes."
    706      */
    707 #   ifdef _LP64
    708 #       define U_SIZEOF_WCHAR_T 4
    709 #   else
    710 #       define U_SIZEOF_WCHAR_T 2
    711 #   endif
    712 #elif U_PLATFORM == U_PF_OS400
    713 #   if defined(__UTF32__)
    714         /*
    715          * LOCALETYPE(*LOCALEUTF) is specified.
    716          * Wide-character strings are in UTF-32,
    717          * narrow-character strings are in UTF-8.
    718          */
    719 #       define U_SIZEOF_WCHAR_T 4
    720 #   elif defined(__UCS2__)
    721         /*
    722          * LOCALETYPE(*LOCALEUCS2) is specified.
    723          * Wide-character strings are in UCS-2,
    724          * narrow-character strings are in EBCDIC.
    725          */
    726 #       define U_SIZEOF_WCHAR_T 2
    727 #else
    728         /*
    729          * LOCALETYPE(*CLD) or LOCALETYPE(*LOCALE) is specified.
    730          * Wide-character strings are in 16-bit EBCDIC,
    731          * narrow-character strings are in EBCDIC.
    732          */
    733 #       define U_SIZEOF_WCHAR_T 2
    734 #   endif
    735 #else
    736 #   define U_SIZEOF_WCHAR_T 4
    737 #endif
    738 
    739 #ifndef U_HAVE_WCSCPY
    740 #define U_HAVE_WCSCPY U_HAVE_WCHAR_H
    741 #endif
    742 
    743 /** @} */
    744 
    745 /**
    746  * \def U_HAVE_CHAR16_T
    747  * Defines whether the char16_t type is available for UTF-16
    748  * and u"abc" UTF-16 string literals are supported.
    749  * This is a new standard type and standard string literal syntax in C++0x
    750  * but has been available in some compilers before.
    751  * @internal
    752  */
    753 #ifdef U_HAVE_CHAR16_T
    754     /* Use the predefined value. */
    755 #else
    756     /*
    757      * Notes:
    758      * Visual Studio 10 (_MSC_VER>=1600) defines char16_t but
    759      * does not support u"abc" string literals.
    760      * gcc 4.4 defines the __CHAR16_TYPE__ macro to a usable type but
    761      * does not support u"abc" string literals.
    762      * C++11 and C11 require support for UTF-16 literals
    763      * TODO: Fix for plain C. Doesn't work on Mac.
    764      */
    765 #   if U_CPLUSPLUS_VERSION >= 11 || (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L)
    766 #       define U_HAVE_CHAR16_T 1
    767 #   else
    768 #       define U_HAVE_CHAR16_T 0
    769 #   endif
    770 #endif
    771 
    772 /**
    773  * @{
    774  * \def U_DECLARE_UTF16
    775  * Do not use this macro because it is not defined on all platforms.
    776  * Use the UNICODE_STRING or U_STRING_DECL macros instead.
    777  * @internal
    778  */
    779 #ifdef U_DECLARE_UTF16
    780     /* Use the predefined value. */
    781 #elif U_HAVE_CHAR16_T \
    782     || (defined(__xlC__) && defined(__IBM_UTF_LITERAL) && U_SIZEOF_WCHAR_T != 2) \
    783     || (defined(__HP_aCC) && __HP_aCC >= 035000) \
    784     || (defined(__HP_cc) && __HP_cc >= 111106)
    785 #   define U_DECLARE_UTF16(string) u ## string
    786 #elif U_SIZEOF_WCHAR_T == 2 \
    787     && (U_CHARSET_FAMILY == 0 || (U_PF_OS390 <= U_PLATFORM && U_PLATFORM <= U_PF_OS400 && defined(__UCS2__)))
    788 #   define U_DECLARE_UTF16(string) L ## string
    789 #else
    790     /* Leave U_DECLARE_UTF16 undefined. See unistr.h. */
    791 #endif
    792 
    793 /** @} */
    794 
    795 /*===========================================================================*/
    796 /** @{ Symbol import-export control                                          */
    797 /*===========================================================================*/
    798 
    799 #ifdef U_EXPORT
    800     /* Use the predefined value. */
    801 #elif defined(U_STATIC_IMPLEMENTATION)
    802 #   define U_EXPORT
    803 #elif defined(__GNUC__)
    804 #   define U_EXPORT __attribute__((visibility("default")))
    805 #elif (defined(__SUNPRO_CC) && __SUNPRO_CC >= 0x550) \
    806    || (defined(__SUNPRO_C) && __SUNPRO_C >= 0x550)
    807 #   define U_EXPORT __global
    808 /*#elif defined(__HP_aCC) || defined(__HP_cc)
    809 #   define U_EXPORT __declspec(dllexport)*/
    810 #elif defined(_MSC_VER)
    811 #   define U_EXPORT __declspec(dllexport)
    812 #else
    813 #   define U_EXPORT
    814 #endif
    815 
    816 /* U_CALLCONV is releated to U_EXPORT2 */
    817 #ifdef U_EXPORT2
    818     /* Use the predefined value. */
    819 #elif defined(_MSC_VER)
    820 #   define U_EXPORT2 __cdecl
    821 #else
    822 #   define U_EXPORT2
    823 #endif
    824 
    825 #ifdef U_IMPORT
    826     /* Use the predefined value. */
    827 #elif defined(_MSC_VER)
    828     /* Windows needs to export/import data. */
    829 #   define U_IMPORT __declspec(dllimport)
    830 #else
    831 #   define U_IMPORT
    832 #endif
    833 
    834 /**
    835  * \def U_CALLCONV
    836  * Similar to U_CDECL_BEGIN/U_CDECL_END, this qualifier is necessary
    837  * in callback function typedefs to make sure that the calling convention
    838  * is compatible.
    839  *
    840  * This is only used for non-ICU-API functions.
    841  * When a function is a public ICU API,
    842  * you must use the U_CAPI and U_EXPORT2 qualifiers.
    843  *
    844  * Please note, you need to use U_CALLCONV after the *.
    845  *
    846  * NO : "static const char U_CALLCONV *func( . . . )"
    847  * YES: "static const char* U_CALLCONV func( . . . )"
    848  *
    849  * @stable ICU 2.0
    850  */
    851 #if U_PLATFORM == U_PF_OS390 && defined(__cplusplus)
    852 #    define U_CALLCONV __cdecl
    853 #else
    854 #    define U_CALLCONV U_EXPORT2
    855 #endif
    856 
    857 /**
    858  * \def U_CALLCONV_FPTR
    859  * Similar to U_CALLCONV, but only used on function pointers.
    860  * @internal
    861  */
    862 #if U_PLATFORM == U_PF_OS390 && defined(__cplusplus)
    863 #    define U_CALLCONV_FPTR U_CALLCONV
    864 #else
    865 #    define U_CALLCONV_FPTR
    866 #endif
    867 /* @} */
    868 
    869 #endif
    870