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# alloca.m4 serial 21
dnl Copyright (C) 2002-2004, 2006-2007, 2009-2023 Free Software Foundation,
dnl Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
AC_DEFUN([gl_FUNC_ALLOCA],
[
AC_REQUIRE([AC_FUNC_ALLOCA])
if test $ac_cv_func_alloca_works = no; then
gl_PREREQ_ALLOCA
fi
# Define an additional variable used in the Makefile substitution.
if test $ac_cv_working_alloca_h = yes; then
AC_CACHE_CHECK([for alloca as a compiler built-in], [gl_cv_rpl_alloca], [
AC_EGREP_CPP([Need own alloca], [
#if defined __GNUC__ || defined _AIX || defined _MSC_VER
Need own alloca
#endif
], [gl_cv_rpl_alloca=yes], [gl_cv_rpl_alloca=no])
])
if test $gl_cv_rpl_alloca = yes; then
dnl OK, alloca can be implemented through a compiler built-in.
AC_DEFINE([HAVE_ALLOCA], [1],
[Define to 1 if you have 'alloca' after including <alloca.h>,
a header that may be supplied by this distribution.])
GL_GENERATE_ALLOCA_H=true
else
dnl alloca exists as a library function, i.e. it is slow and probably
dnl a memory leak. Don't define HAVE_ALLOCA in this case.
GL_GENERATE_ALLOCA_H=false
fi
else
GL_GENERATE_ALLOCA_H=true
fi
if test $ac_cv_working_alloca_h = yes; then
HAVE_ALLOCA_H=1
else
HAVE_ALLOCA_H=0
fi
AC_SUBST([HAVE_ALLOCA_H])
])
# Prerequisites of lib/alloca.c.
# STACK_DIRECTION is already handled by AC_FUNC_ALLOCA.
AC_DEFUN([gl_PREREQ_ALLOCA], [:])
m4_version_prereq([2.70], [], [
# This works around a bug in autoconf <= 2.68 and has simplifications
# from 2.70. See:
# https://lists.gnu.org/r/bug-gnulib/2011-06/msg00277.html
# https://git.savannah.gnu.org/cgit/autoconf.git/commit/?id=6cd9f12520b0d6f76d3230d7565feba1ecf29497
# https://git.savannah.gnu.org/cgit/autoconf.git/commit/?id=15edf7fd8094fd14a89d9891dd72a9624762597a
# _AC_LIBOBJ_ALLOCA
# -----------------
# Set up the LIBOBJ replacement of 'alloca'. Well, not exactly
# AC_LIBOBJ since we actually set the output variable 'ALLOCA'.
# Nevertheless, for Automake, AC_LIBSOURCES it.
m4_define([_AC_LIBOBJ_ALLOCA],
[# The SVR3 libPW and SVR4 libucb both contain incompatible functions
# that cause trouble. Some versions do not even contain alloca or
# contain a buggy version. If you still want to use their alloca,
# use ar to extract alloca.o from them instead of compiling alloca.c.
AC_LIBSOURCES(alloca.c)
AC_SUBST([ALLOCA], [\${LIBOBJDIR}alloca.$ac_objext])dnl
AC_DEFINE(C_ALLOCA, 1, [Define to 1 if using 'alloca.c'.])
AC_CACHE_CHECK([stack direction for C alloca],
[ac_cv_c_stack_direction],
[AC_RUN_IFELSE([AC_LANG_SOURCE(
[AC_INCLUDES_DEFAULT
int
find_stack_direction (int *addr, int depth)
{
int dir, dummy = 0;
if (! addr)
addr = &dummy;
*addr = addr < &dummy ? 1 : addr == &dummy ? 0 : -1;
dir = depth ? find_stack_direction (addr, depth - 1) : 0;
return dir + dummy;
}
int
main (int argc, char **argv)
{
return find_stack_direction (0, argc + !argv + 20) < 0;
}])],
[ac_cv_c_stack_direction=1],
[ac_cv_c_stack_direction=-1],
[ac_cv_c_stack_direction=0])])
AH_VERBATIM([STACK_DIRECTION],
[/* If using the C implementation of alloca, define if you know the
direction of stack growth for your system; otherwise it will be
automatically deduced at runtime.
STACK_DIRECTION > 0 => grows toward higher addresses
STACK_DIRECTION < 0 => grows toward lower addresses
STACK_DIRECTION = 0 => direction of growth unknown */
#undef STACK_DIRECTION])dnl
AC_DEFINE_UNQUOTED(STACK_DIRECTION, $ac_cv_c_stack_direction)
])# _AC_LIBOBJ_ALLOCA
])
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