1# size_max.m4 serial 9 2dnl Copyright (C) 2003, 2005-2006, 2008-2010 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 7dnl From Bruno Haible. 8 9AC_DEFUN([gl_SIZE_MAX], 10[ 11 AC_CHECK_HEADERS([stdint.h]) 12 dnl First test whether the system already has SIZE_MAX. 13 AC_CACHE_CHECK([for SIZE_MAX], [gl_cv_size_max], [ 14 gl_cv_size_max= 15 AC_EGREP_CPP([Found it], [ 16#include <limits.h> 17#if HAVE_STDINT_H 18#include <stdint.h> 19#endif 20#ifdef SIZE_MAX 21Found it 22#endif 23], [gl_cv_size_max=yes]) 24 if test -z "$gl_cv_size_max"; then 25 dnl Define it ourselves. Here we assume that the type 'size_t' is not wider 26 dnl than the type 'unsigned long'. Try hard to find a definition that can 27 dnl be used in a preprocessor #if, i.e. doesn't contain a cast. 28 AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1], 29 [#include <stddef.h> 30#include <limits.h>], [size_t_bits_minus_1=]) 31 AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)], 32 [#include <stddef.h>], [fits_in_uint=]) 33 if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then 34 if test $fits_in_uint = 1; then 35 dnl Even though SIZE_MAX fits in an unsigned int, it must be of type 36 dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'. 37 AC_TRY_COMPILE([#include <stddef.h> 38 extern size_t foo; 39 extern unsigned long foo; 40 ], [], [fits_in_uint=0]) 41 fi 42 dnl We cannot use 'expr' to simplify this expression, because 'expr' 43 dnl works only with 'long' integers in the host environment, while we 44 dnl might be cross-compiling from a 32-bit platform to a 64-bit platform. 45 if test $fits_in_uint = 1; then 46 gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)" 47 else 48 gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)" 49 fi 50 else 51 dnl Shouldn't happen, but who knows... 52 gl_cv_size_max='((size_t)~(size_t)0)' 53 fi 54 fi 55 ]) 56 if test "$gl_cv_size_max" != yes; then 57 AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max], 58 [Define as the maximum value of type 'size_t', if the system doesn't define it.]) 59 fi 60 dnl Don't redefine SIZE_MAX in config.h if config.h is re-included after 61 dnl <stdint.h>. Remember that the #undef in AH_VERBATIM gets replaced with 62 dnl #define by AC_DEFINE_UNQUOTED. 63 AH_VERBATIM([SIZE_MAX], 64[/* Define as the maximum value of type 'size_t', if the system doesn't define 65 it. */ 66#ifndef SIZE_MAX 67# undef SIZE_MAX 68#endif]) 69]) 70 71dnl Autoconf >= 2.61 has AC_COMPUTE_INT built-in. 72dnl Remove this when we can assume autoconf >= 2.61. 73m4_ifdef([AC_COMPUTE_INT], [], [ 74 AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])]) 75]) 76