1 # alloca.m4 serial 21 2 dnl Copyright (C) 2002-2004, 2006-2007, 2009-2022 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 GL_GENERATE_ALLOCA_H=true 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 GL_GENERATE_ALLOCA_H=false 34 fi 35 else 36 GL_GENERATE_ALLOCA_H=true 37 fi 38 39 if test $ac_cv_working_alloca_h = yes; then 40 HAVE_ALLOCA_H=1 41 else 42 HAVE_ALLOCA_H=0 43 fi 44 AC_SUBST([HAVE_ALLOCA_H]) 45 ]) 46 47 # Prerequisites of lib/alloca.c. 48 # STACK_DIRECTION is already handled by AC_FUNC_ALLOCA. 49 AC_DEFUN([gl_PREREQ_ALLOCA], [:]) 50 51 m4_version_prereq([2.70], [], [ 52 53 # This works around a bug in autoconf <= 2.68 and has simplifications 54 # from 2.70. See: 55 # https://lists.gnu.org/r/bug-gnulib/2011-06/msg00277.html 56 # https://git.savannah.gnu.org/cgit/autoconf.git/commit/?id=6cd9f12520b0d6f76d3230d7565feba1ecf29497 57 # https://git.savannah.gnu.org/cgit/autoconf.git/commit/?id=15edf7fd8094fd14a89d9891dd72a9624762597a 58 59 # _AC_LIBOBJ_ALLOCA 60 # ----------------- 61 # Set up the LIBOBJ replacement of 'alloca'. Well, not exactly 62 # AC_LIBOBJ since we actually set the output variable 'ALLOCA'. 63 # Nevertheless, for Automake, AC_LIBSOURCES it. 64 m4_define([_AC_LIBOBJ_ALLOCA], 65 [# The SVR3 libPW and SVR4 libucb both contain incompatible functions 66 # that cause trouble. Some versions do not even contain alloca or 67 # contain a buggy version. If you still want to use their alloca, 68 # use ar to extract alloca.o from them instead of compiling alloca.c. 69 AC_LIBSOURCES(alloca.c) 70 AC_SUBST([ALLOCA], [\${LIBOBJDIR}alloca.$ac_objext])dnl 71 AC_DEFINE(C_ALLOCA, 1, [Define to 1 if using 'alloca.c'.]) 72 73 AC_CACHE_CHECK([stack direction for C alloca], 74 [ac_cv_c_stack_direction], 75 [AC_RUN_IFELSE([AC_LANG_SOURCE( 76 [AC_INCLUDES_DEFAULT 77 int 78 find_stack_direction (int *addr, int depth) 79 { 80 int dir, dummy = 0; 81 if (! addr) 82 addr = &dummy; 83 *addr = addr < &dummy ? 1 : addr == &dummy ? 0 : -1; 84 dir = depth ? find_stack_direction (addr, depth - 1) : 0; 85 return dir + dummy; 86 } 87 88 int 89 main (int argc, char **argv) 90 { 91 return find_stack_direction (0, argc + !argv + 20) < 0; 92 }])], 93 [ac_cv_c_stack_direction=1], 94 [ac_cv_c_stack_direction=-1], 95 [ac_cv_c_stack_direction=0])]) 96 AH_VERBATIM([STACK_DIRECTION], 97 [/* If using the C implementation of alloca, define if you know the 98 direction of stack growth for your system; otherwise it will be 99 automatically deduced at runtime. 100 STACK_DIRECTION > 0 => grows toward higher addresses 101 STACK_DIRECTION < 0 => grows toward lower addresses 102 STACK_DIRECTION = 0 => direction of growth unknown */ 103 #undef STACK_DIRECTION])dnl 104 AC_DEFINE_UNQUOTED(STACK_DIRECTION, $ac_cv_c_stack_direction) 105 ])# _AC_LIBOBJ_ALLOCA 106 ]) 107
Indexes created Sat Apr 11 00:22:22 UTC 2026