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      1 # alloca.m4 serial 14
      2 dnl Copyright (C) 2002-2004, 2006-2007, 2009-2012 Free Software Foundation,
      3 dnl Inc.
      4 dnl This file is free software; the Free Software Foundation
      5 dnl gives unlimited permission to copy and/or distribute it,
      6 dnl with or without modifications, as long as this notice is preserved.
      7 
      8 AC_DEFUN([gl_FUNC_ALLOCA],
      9 [
     10   AC_REQUIRE([AC_FUNC_ALLOCA])
     11   if test $ac_cv_func_alloca_works = no; then
     12     gl_PREREQ_ALLOCA
     13   fi
     14 
     15   # Define an additional variable used in the Makefile substitution.
     16   if test $ac_cv_working_alloca_h = yes; then
     17     AC_CACHE_CHECK([for alloca as a compiler built-in], [gl_cv_rpl_alloca], [
     18       AC_EGREP_CPP([Need own alloca], [
     19 #if defined __GNUC__ || defined _AIX || defined _MSC_VER
     20         Need own alloca
     21 #endif
     22         ], [gl_cv_rpl_alloca=yes], [gl_cv_rpl_alloca=no])
     23     ])
     24     if test $gl_cv_rpl_alloca = yes; then
     25       dnl OK, alloca can be implemented through a compiler built-in.
     26       AC_DEFINE([HAVE_ALLOCA], [1],
     27         [Define to 1 if you have 'alloca' after including <alloca.h>,
     28          a header that may be supplied by this distribution.])
     29       ALLOCA_H=alloca.h
     30     else
     31       dnl alloca exists as a library function, i.e. it is slow and probably
     32       dnl a memory leak. Don't define HAVE_ALLOCA in this case.
     33       ALLOCA_H=
     34     fi
     35   else
     36     ALLOCA_H=alloca.h
     37   fi
     38   AC_SUBST([ALLOCA_H])
     39   AM_CONDITIONAL([GL_GENERATE_ALLOCA_H], [test -n "$ALLOCA_H"])
     40 ])
     41 
     42 # Prerequisites of lib/alloca.c.
     43 # STACK_DIRECTION is already handled by AC_FUNC_ALLOCA.
     44 AC_DEFUN([gl_PREREQ_ALLOCA], [:])
     45 
     46 # This works around a bug in autoconf <= 2.68.
     47 # See <http://lists.gnu.org/archive/html/bug-gnulib/2011-06/msg00277.html>.
     48 
     49 m4_version_prereq([2.69], [] ,[
     50 
     51 # This is taken from the following Autoconf patch:
     52 # http://git.savannah.gnu.org/cgit/autoconf.git/commit/?id=6cd9f12520b0d6f76d3230d7565feba1ecf29497
     53 
     54 # _AC_LIBOBJ_ALLOCA
     55 # -----------------
     56 # Set up the LIBOBJ replacement of 'alloca'.  Well, not exactly
     57 # AC_LIBOBJ since we actually set the output variable 'ALLOCA'.
     58 # Nevertheless, for Automake, AC_LIBSOURCES it.
     59 m4_define([_AC_LIBOBJ_ALLOCA],
     60 [# The SVR3 libPW and SVR4 libucb both contain incompatible functions
     61 # that cause trouble.  Some versions do not even contain alloca or
     62 # contain a buggy version.  If you still want to use their alloca,
     63 # use ar to extract alloca.o from them instead of compiling alloca.c.
     64 AC_LIBSOURCES(alloca.c)
     65 AC_SUBST([ALLOCA], [\${LIBOBJDIR}alloca.$ac_objext])dnl
     66 AC_DEFINE(C_ALLOCA, 1, [Define to 1 if using 'alloca.c'.])
     67 
     68 AC_CACHE_CHECK(whether 'alloca.c' needs Cray hooks, ac_cv_os_cray,
     69 [AC_EGREP_CPP(webecray,
     70 [#if defined CRAY && ! defined CRAY2
     71 webecray
     72 #else
     73 wenotbecray
     74 #endif
     75 ], ac_cv_os_cray=yes, ac_cv_os_cray=no)])
     76 if test $ac_cv_os_cray = yes; then
     77   for ac_func in _getb67 GETB67 getb67; do
     78     AC_CHECK_FUNC($ac_func,
     79                   [AC_DEFINE_UNQUOTED(CRAY_STACKSEG_END, $ac_func,
     80                                       [Define to one of '_getb67', 'GETB67',
     81                                        'getb67' for Cray-2 and Cray-YMP
     82                                        systems. This function is required for
     83                                        'alloca.c' support on those systems.])
     84     break])
     85   done
     86 fi
     87 
     88 AC_CACHE_CHECK([stack direction for C alloca],
     89                [ac_cv_c_stack_direction],
     90 [AC_RUN_IFELSE([AC_LANG_SOURCE(
     91 [AC_INCLUDES_DEFAULT
     92 int
     93 find_stack_direction (int *addr, int depth)
     94 {
     95   int dir, dummy = 0;
     96   if (! addr)
     97     addr = &dummy;
     98   *addr = addr < &dummy ? 1 : addr == &dummy ? 0 : -1;
     99   dir = depth ? find_stack_direction (addr, depth - 1) : 0;
    100   return dir + dummy;
    101 }
    102 
    103 int
    104 main (int argc, char **argv)
    105 {
    106   return find_stack_direction (0, argc + !argv + 20) < 0;
    107 }])],
    108                [ac_cv_c_stack_direction=1],
    109                [ac_cv_c_stack_direction=-1],
    110                [ac_cv_c_stack_direction=0])])
    111 AH_VERBATIM([STACK_DIRECTION],
    112 [/* If using the C implementation of alloca, define if you know the
    113    direction of stack growth for your system; otherwise it will be
    114    automatically deduced at runtime.
    115         STACK_DIRECTION > 0 => grows toward higher addresses
    116         STACK_DIRECTION < 0 => grows toward lower addresses
    117         STACK_DIRECTION = 0 => direction of growth unknown */
    118 @%:@undef STACK_DIRECTION])dnl
    119 AC_DEFINE_UNQUOTED(STACK_DIRECTION, $ac_cv_c_stack_direction)
    120 ])# _AC_LIBOBJ_ALLOCA
    121 ])
    122