1# malloc.m4 serial 28 2dnl Copyright (C) 2007, 2009-2022 Free Software Foundation, Inc. 3dnl This file is free software; the Free Software Foundation 4dnl gives unlimited permission to copy and/or distribute it, 5dnl with or without modifications, as long as this notice is preserved. 6 7# This is adapted with modifications from upstream Autoconf here: 8# https://git.savannah.gnu.org/cgit/autoconf.git/tree/lib/autoconf/functions.m4?id=v2.70#n949 9AC_DEFUN([_AC_FUNC_MALLOC_IF], 10[ 11 AC_REQUIRE([AC_CANONICAL_HOST])dnl for cross-compiles 12 AC_CACHE_CHECK([whether malloc (0) returns nonnull], 13 [ac_cv_func_malloc_0_nonnull], 14 [AC_RUN_IFELSE( 15 [AC_LANG_PROGRAM( 16 [[#include <stdlib.h> 17 ]], 18 [[void *p = malloc (0); 19 int result = !p; 20 free (p); 21 return result;]]) 22 ], 23 [ac_cv_func_malloc_0_nonnull=yes], 24 [ac_cv_func_malloc_0_nonnull=no], 25 [case "$host_os" in 26 # Guess yes on platforms where we know the result. 27 *-gnu* | freebsd* | netbsd* | openbsd* | bitrig* \ 28 | gnu* | *-musl* | midnightbsd* \ 29 | hpux* | solaris* | cygwin* | mingw* | msys* ) 30 ac_cv_func_malloc_0_nonnull="guessing yes" ;; 31 # If we don't know, obey --enable-cross-guesses. 32 *) ac_cv_func_malloc_0_nonnull="$gl_cross_guess_normal" ;; 33 esac 34 ]) 35 ]) 36 AS_CASE([$ac_cv_func_malloc_0_nonnull], [*yes], [$1], [$2]) 37])# _AC_FUNC_MALLOC_IF 38 39# gl_FUNC_MALLOC_GNU 40# ------------------ 41# Replace malloc if it is not compatible with GNU libc. 42AC_DEFUN([gl_FUNC_MALLOC_GNU], 43[ 44 AC_REQUIRE([gl_STDLIB_H_DEFAULTS]) 45 AC_REQUIRE([gl_FUNC_MALLOC_POSIX]) 46 REPLACE_MALLOC_FOR_MALLOC_GNU="$REPLACE_MALLOC_FOR_MALLOC_POSIX" 47 if test $REPLACE_MALLOC_FOR_MALLOC_GNU = 0; then 48 _AC_FUNC_MALLOC_IF([], [REPLACE_MALLOC_FOR_MALLOC_GNU=1]) 49 fi 50]) 51 52# gl_FUNC_MALLOC_PTRDIFF 53# ---------------------- 54# Test whether malloc (N) reliably fails when N exceeds PTRDIFF_MAX, 55# and replace malloc otherwise. 56AC_DEFUN([gl_FUNC_MALLOC_PTRDIFF], 57[ 58 AC_REQUIRE([gl_STDLIB_H_DEFAULTS]) 59 AC_REQUIRE([gl_CHECK_MALLOC_PTRDIFF]) 60 test "$gl_cv_malloc_ptrdiff" = yes || REPLACE_MALLOC_FOR_MALLOC_POSIX=1 61]) 62 63# Test whether malloc, realloc, calloc refuse to create objects 64# larger than what can be expressed in ptrdiff_t. 65# Set gl_cv_func_malloc_gnu to yes or no accordingly. 66AC_DEFUN([gl_CHECK_MALLOC_PTRDIFF], 67[ 68 AC_CACHE_CHECK([whether malloc is ptrdiff_t safe], 69 [gl_cv_malloc_ptrdiff], 70 [AC_COMPILE_IFELSE( 71 [AC_LANG_PROGRAM( 72 [[#include <stdint.h> 73 ]], 74 [[/* 64-bit ptrdiff_t is so wide that no practical platform 75 can exceed it. */ 76 #define WIDE_PTRDIFF (PTRDIFF_MAX >> 31 >> 31 != 0) 77 78 /* On rare machines where size_t fits in ptrdiff_t there 79 is no problem. */ 80 #define NARROW_SIZE (SIZE_MAX <= PTRDIFF_MAX) 81 82 /* glibc 2.30 and later malloc refuses to exceed ptrdiff_t 83 bounds even on 32-bit platforms. We don't know which 84 non-glibc systems are safe. */ 85 #define KNOWN_SAFE (2 < __GLIBC__ + (30 <= __GLIBC_MINOR__)) 86 87 #if WIDE_PTRDIFF || NARROW_SIZE || KNOWN_SAFE 88 return 0; 89 #else 90 #error "malloc might not be ptrdiff_t safe" 91 syntax error 92 #endif 93 ]])], 94 [gl_cv_malloc_ptrdiff=yes], 95 [gl_cv_malloc_ptrdiff=no]) 96 ]) 97]) 98 99# gl_FUNC_MALLOC_POSIX 100# -------------------- 101# Test whether 'malloc' is POSIX compliant (sets errno to ENOMEM when it 102# fails, and doesn't mess up with ptrdiff_t overflow), and replace 103# malloc if it is not. 104AC_DEFUN([gl_FUNC_MALLOC_POSIX], 105[ 106 AC_REQUIRE([gl_STDLIB_H_DEFAULTS]) 107 AC_REQUIRE([gl_FUNC_MALLOC_PTRDIFF]) 108 AC_REQUIRE([gl_CHECK_MALLOC_POSIX]) 109 if test "$gl_cv_func_malloc_posix" = yes; then 110 AC_DEFINE([HAVE_MALLOC_POSIX], [1], 111 [Define if malloc, realloc, and calloc set errno on allocation failure.]) 112 else 113 REPLACE_MALLOC_FOR_MALLOC_POSIX=1 114 fi 115]) 116 117# Test whether malloc, realloc, calloc set errno to ENOMEM on failure. 118# Set gl_cv_func_malloc_posix to yes or no accordingly. 119AC_DEFUN([gl_CHECK_MALLOC_POSIX], 120[ 121 AC_REQUIRE([AC_CANONICAL_HOST]) 122 AC_CACHE_CHECK([whether malloc, realloc, calloc set errno on failure], 123 [gl_cv_func_malloc_posix], 124 [ 125 dnl It is too dangerous to try to allocate a large amount of memory: 126 dnl some systems go to their knees when you do that. So assume that 127 dnl all Unix implementations of the function set errno on failure, 128 dnl except on those platforms where we have seen 'test-malloc-gnu', 129 dnl 'test-realloc-gnu', 'test-calloc-gnu' fail. 130 case "$host_os" in 131 mingw*) 132 gl_cv_func_malloc_posix=no ;; 133 irix* | solaris*) 134 dnl On IRIX 6.5, the three functions return NULL with errno unset 135 dnl when the argument is larger than PTRDIFF_MAX. 136 dnl On Solaris 11.3, the three functions return NULL with errno set 137 dnl to EAGAIN, not ENOMEM, when the argument is larger than 138 dnl PTRDIFF_MAX. 139 dnl Here is a test program: 140m4_divert_push([KILL]) 141#include <errno.h> 142#include <stdio.h> 143#include <stdlib.h> 144#define ptrdiff_t long 145#ifndef PTRDIFF_MAX 146# define PTRDIFF_MAX ((ptrdiff_t) ((1UL << (8 * sizeof (ptrdiff_t) - 1)) - 1)) 147#endif 148 149int main () 150{ 151 void *p; 152 153 fprintf (stderr, "PTRDIFF_MAX = %lu\n", (unsigned long) PTRDIFF_MAX); 154 155 errno = 0; 156 p = malloc ((unsigned long) PTRDIFF_MAX + 1); 157 fprintf (stderr, "p=%p errno=%d\n", p, errno); 158 159 errno = 0; 160 p = calloc (PTRDIFF_MAX / 2 + 1, 2); 161 fprintf (stderr, "p=%p errno=%d\n", p, errno); 162 163 errno = 0; 164 p = realloc (NULL, (unsigned long) PTRDIFF_MAX + 1); 165 fprintf (stderr, "p=%p errno=%d\n", p, errno); 166 167 return 0; 168} 169m4_divert_pop([KILL]) 170 gl_cv_func_malloc_posix=no ;; 171 *) 172 gl_cv_func_malloc_posix=yes ;; 173 esac 174 ]) 175]) 176