gnulib/import/m4/alloca.m4

   1 # alloca.m4 serial 15
   2 dnl Copyright (C) 2002-2004, 2006-2007, 2009-2019 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   if test $ac_cv_working_alloca_h = yes; then
  42     HAVE_ALLOCA_H=1
  43   else
  44     HAVE_ALLOCA_H=0
  45   fi
  46   AC_SUBST([HAVE_ALLOCA_H])
  47 ])
  48
  49 # Prerequisites of lib/alloca.c.
  50 # STACK_DIRECTION is already handled by AC_FUNC_ALLOCA.
  51 AC_DEFUN([gl_PREREQ_ALLOCA], [:])
  52
  53 # This works around a bug in autoconf <= 2.68.
  54 # See <https://lists.gnu.org/r/bug-gnulib/2011-06/msg00277.html>.
  55
  56 m4_version_prereq([2.69], [] ,[
  57
  58 # This is taken from the following Autoconf patch:
  59 # https://git.savannah.gnu.org/gitweb/?p=autoconf.git;a=commitdiff;h=6cd9f12520b0d6f76d3230d7565feba1ecf29497
  60
  61 # _AC_LIBOBJ_ALLOCA
  62 # -----------------
  63 # Set up the LIBOBJ replacement of 'alloca'.  Well, not exactly
  64 # AC_LIBOBJ since we actually set the output variable 'ALLOCA'.
  65 # Nevertheless, for Automake, AC_LIBSOURCES it.
  66 m4_define([_AC_LIBOBJ_ALLOCA],
  67 [# The SVR3 libPW and SVR4 libucb both contain incompatible functions
  68 # that cause trouble.  Some versions do not even contain alloca or
  69 # contain a buggy version.  If you still want to use their alloca,
  70 # use ar to extract alloca.o from them instead of compiling alloca.c.
  71 AC_LIBSOURCES(alloca.c)
  72 AC_SUBST([ALLOCA], [\${LIBOBJDIR}alloca.$ac_objext])dnl
  73 AC_DEFINE(C_ALLOCA, 1, [Define to 1 if using 'alloca.c'.])
  74
  75 AC_CACHE_CHECK(whether 'alloca.c' needs Cray hooks, ac_cv_os_cray,
  76 [AC_EGREP_CPP(webecray,
  77 [#if defined CRAY && ! defined CRAY2
  78 webecray
  79 #else
  80 wenotbecray
  81 #endif
  82 ], ac_cv_os_cray=yes, ac_cv_os_cray=no)])
  83 if test $ac_cv_os_cray = yes; then
  84   for ac_func in _getb67 GETB67 getb67; do
  85     AC_CHECK_FUNC($ac_func,
  86                   [AC_DEFINE_UNQUOTED(CRAY_STACKSEG_END, $ac_func,
  87                                       [Define to one of '_getb67', 'GETB67',
  88                                        'getb67' for Cray-2 and Cray-YMP
  89                                        systems. This function is required for
  90                                        'alloca.c' support on those systems.])
  91     break])
  92   done
  93 fi
  94
  95 AC_CACHE_CHECK([stack direction for C alloca],
  96                [ac_cv_c_stack_direction],
  97 [AC_RUN_IFELSE([AC_LANG_SOURCE(
  98 [AC_INCLUDES_DEFAULT
  99 int
 100 find_stack_direction (int *addr, int depth)
 101 {
 102   int dir, dummy = 0;
 103   if (! addr)
 104     addr = &dummy;
 105   *addr = addr < &dummy ? 1 : addr == &dummy ? 0 : -1;
 106   dir = depth ? find_stack_direction (addr, depth - 1) : 0;
 107   return dir + dummy;
 108 }
 109
 110 int
 111 main (int argc, char **argv)
 112 {
 113   return find_stack_direction (0, argc + !argv + 20) < 0;
 114 }])],
 115                [ac_cv_c_stack_direction=1],
 116                [ac_cv_c_stack_direction=-1],
 117                [ac_cv_c_stack_direction=0])])
 118 AH_VERBATIM([STACK_DIRECTION],
 119 [/* If using the C implementation of alloca, define if you know the
 120    direction of stack growth for your system; otherwise it will be
 121    automatically deduced at runtime.
 122         STACK_DIRECTION > 0 => grows toward higher addresses
 123         STACK_DIRECTION < 0 => grows toward lower addresses
 124         STACK_DIRECTION = 0 => direction of growth unknown */
 125 @%:@undef STACK_DIRECTION])dnl
 126 AC_DEFINE_UNQUOTED(STACK_DIRECTION, $ac_cv_c_stack_direction)
 127 ])# _AC_LIBOBJ_ALLOCA
 128 ])