1# size_max.m4 serial 6 2dnl Copyright (C) 2003, 2005-2006, 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. 8dnl Change by Vincent Lefevre: added <inttypes.h> for consistency with MPFR 9 10AC_DEFUN([gl_SIZE_MAX], 11[ 12 AC_CHECK_HEADERS(stdint.h) 13 dnl First test whether the system already has SIZE_MAX. 14 AC_MSG_CHECKING([for SIZE_MAX]) 15 AC_CACHE_VAL([gl_cv_size_max], [ 16 gl_cv_size_max= 17 AC_EGREP_CPP([Found it], [ 18#include <limits.h> 19#ifdef HAVE_INTTYPES_H 20# include <inttypes.h> 21#endif 22#if HAVE_STDINT_H 23# include <stdint.h> 24#endif 25#ifdef SIZE_MAX 26Found it 27#endif 28], gl_cv_size_max=yes) 29 if test -z "$gl_cv_size_max"; then 30 dnl Define it ourselves. Here we assume that the type 'size_t' is not wider 31 dnl than the type 'unsigned long'. Try hard to find a definition that can 32 dnl be used in a preprocessor #if, i.e. doesn't contain a cast. 33 AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1], 34 [#include <stddef.h> 35#include <limits.h>], size_t_bits_minus_1=) 36 AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)], 37 [#include <stddef.h>], fits_in_uint=) 38 if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then 39 if test $fits_in_uint = 1; then 40 dnl Even though SIZE_MAX fits in an unsigned int, it must be of type 41 dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'. 42 AC_TRY_COMPILE([#include <stddef.h> 43 extern size_t foo; 44 extern unsigned long foo; 45 ], [], fits_in_uint=0) 46 fi 47 dnl We cannot use 'expr' to simplify this expression, because 'expr' 48 dnl works only with 'long' integers in the host environment, while we 49 dnl might be cross-compiling from a 32-bit platform to a 64-bit platform. 50 if test $fits_in_uint = 1; then 51 gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)" 52 else 53 gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)" 54 fi 55 else 56 dnl Shouldn't happen, but who knows... 57 gl_cv_size_max='((size_t)~(size_t)0)' 58 fi 59 fi 60 ]) 61 AC_MSG_RESULT([$gl_cv_size_max]) 62 if test "$gl_cv_size_max" != yes; then 63 AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max], 64 [Define as the maximum value of type 'size_t', if the system doesn't define it.]) 65 fi 66]) 67 68dnl Autoconf >= 2.61 has AC_COMPUTE_INT built-in. 69dnl Remove this when we can assume autoconf >= 2.61. 70m4_ifdef([AC_COMPUTE_INT], [], [ 71 AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])]) 72]) 73