1# alloca.m4 serial 15 2dnl Copyright (C) 2002-2004, 2006-2007, 2009-2020 Free Software Foundation, 3dnl Inc. 4dnl This file is free software; the Free Software Foundation 5dnl gives unlimited permission to copy and/or distribute it, 6dnl with or without modifications, as long as this notice is preserved. 7 8AC_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 $ac_cv_working_alloca_h = yes; then 42 HAVE_ALLOCA_H=1 43 else 44 HAVE_ALLOCA_H=0 45 fi 46 AC_SUBST([HAVE_ALLOCA_H]) 47]) 48 49# Prerequisites of lib/alloca.c. 50# STACK_DIRECTION is already handled by AC_FUNC_ALLOCA. 51AC_DEFUN([gl_PREREQ_ALLOCA], [:]) 52 53# This works around a bug in autoconf <= 2.68. 54# See <https://lists.gnu.org/r/bug-gnulib/2011-06/msg00277.html>. 55 56m4_version_prereq([2.69], [] ,[ 57 58# This is taken from the following Autoconf patch: 59# https://git.savannah.gnu.org/gitweb/?p=autoconf.git;a=commitdiff;h=6cd9f12520b0d6f76d3230d7565feba1ecf29497 60 61# _AC_LIBOBJ_ALLOCA 62# ----------------- 63# Set up the LIBOBJ replacement of 'alloca'. Well, not exactly 64# AC_LIBOBJ since we actually set the output variable 'ALLOCA'. 65# Nevertheless, for Automake, AC_LIBSOURCES it. 66m4_define([_AC_LIBOBJ_ALLOCA], 67[# The SVR3 libPW and SVR4 libucb both contain incompatible functions 68# that cause trouble. Some versions do not even contain alloca or 69# contain a buggy version. If you still want to use their alloca, 70# use ar to extract alloca.o from them instead of compiling alloca.c. 71AC_LIBSOURCES(alloca.c) 72AC_SUBST([ALLOCA], [\${LIBOBJDIR}alloca.$ac_objext])dnl 73AC_DEFINE(C_ALLOCA, 1, [Define to 1 if using 'alloca.c'.]) 74 75AC_CACHE_CHECK(whether 'alloca.c' needs Cray hooks, ac_cv_os_cray, 76[AC_EGREP_CPP(webecray, 77[#if defined CRAY && ! defined CRAY2 78webecray 79#else 80wenotbecray 81#endif 82], ac_cv_os_cray=yes, ac_cv_os_cray=no)]) 83if 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 93fi 94 95AC_CACHE_CHECK([stack direction for C alloca], 96 [ac_cv_c_stack_direction], 97[AC_RUN_IFELSE([AC_LANG_SOURCE( 98[AC_INCLUDES_DEFAULT 99int 100find_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 110int 111main (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])]) 118AH_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 126AC_DEFINE_UNQUOTED(STACK_DIRECTION, $ac_cv_c_stack_direction) 127])# _AC_LIBOBJ_ALLOCA 128]) 129