1# size_max.m4 serial 5 2dnl Copyright (C) 2003, 2005-2006 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_MSG_CHECKING([for SIZE_MAX]) 14 AC_CACHE_VAL([gl_cv_size_max], [ 15 gl_cv_size_max= 16 AC_EGREP_CPP([Found it], [ 17#include <limits.h> 18#if HAVE_STDINT_H 19#include <stdint.h> 20#endif 21#ifdef SIZE_MAX 22Found it 23#endif 24], gl_cv_size_max=yes) 25 if test -z "$gl_cv_size_max"; then 26 dnl Define it ourselves. Here we assume that the type 'size_t' is not wider 27 dnl than the type 'unsigned long'. Try hard to find a definition that can 28 dnl be used in a preprocessor #if, i.e. doesn't contain a cast. 29 _AC_COMPUTE_INT([sizeof (size_t) * CHAR_BIT - 1], size_t_bits_minus_1, 30 [#include <stddef.h> 31#include <limits.h>], size_t_bits_minus_1=) 32 _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint, 33 [#include <stddef.h>], fits_in_uint=) 34 if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then 35 if test $fits_in_uint = 1; then 36 dnl Even though SIZE_MAX fits in an unsigned int, it must be of type 37 dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'. 38 AC_TRY_COMPILE([#include <stddef.h> 39 extern size_t foo; 40 extern unsigned long foo; 41 ], [], fits_in_uint=0) 42 fi 43 dnl We cannot use 'expr' to simplify this expression, because 'expr' 44 dnl works only with 'long' integers in the host environment, while we 45 dnl might be cross-compiling from a 32-bit platform to a 64-bit platform. 46 if test $fits_in_uint = 1; then 47 gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)" 48 else 49 gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)" 50 fi 51 else 52 dnl Shouldn't happen, but who knows... 53 gl_cv_size_max='((size_t)~(size_t)0)' 54 fi 55 fi 56 ]) 57 AC_MSG_RESULT([$gl_cv_size_max]) 58 if test "$gl_cv_size_max" != yes; then 59 AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max], 60 [Define as the maximum value of type 'size_t', if the system doesn't define it.]) 61 fi 62]) 63