size_max.m4 (2878B)
1 # size_max.m4 serial 12 2 dnl Copyright (C) 2003, 2005-2006, 2008-2021 Free Software Foundation, Inc. 3 dnl This file is free software; the Free Software Foundation 4 dnl gives unlimited permission to copy and/or distribute it, 5 dnl with or without modifications, as long as this notice is preserved. 6 7 dnl From Bruno Haible. 8 9 AC_PREREQ([2.61]) 10 11 AC_DEFUN([gl_SIZE_MAX], 12 [ 13 AC_CHECK_HEADERS([stdint.h]) 14 dnl First test whether the system already has SIZE_MAX. 15 AC_CACHE_CHECK([for SIZE_MAX], [gl_cv_size_max], [ 16 gl_cv_size_max=no 17 AC_EGREP_CPP([Found it], [ 18 #include <limits.h> 19 #if HAVE_STDINT_H 20 #include <stdint.h> 21 #endif 22 #ifdef SIZE_MAX 23 Found it 24 #endif 25 ], [gl_cv_size_max=yes]) 26 if test $gl_cv_size_max != yes; then 27 dnl Define it ourselves. Here we assume that the type 'size_t' is not wider 28 dnl than the type 'unsigned long'. Try hard to find a definition that can 29 dnl be used in a preprocessor #if, i.e. doesn't contain a cast. 30 AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1], 31 [#include <stddef.h> 32 #include <limits.h>], [size_t_bits_minus_1=]) 33 AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)], 34 [#include <stddef.h>], [fits_in_uint=]) 35 if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then 36 if test $fits_in_uint = 1; then 37 dnl Even though SIZE_MAX fits in an unsigned int, it must be of type 38 dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'. 39 AC_COMPILE_IFELSE( 40 [AC_LANG_PROGRAM( 41 [[#include <stddef.h> 42 extern size_t foo; 43 extern unsigned long foo; 44 ]], 45 [[]])], 46 [fits_in_uint=0]) 47 fi 48 dnl We cannot use 'expr' to simplify this expression, because 'expr' 49 dnl works only with 'long' integers in the host environment, while we 50 dnl might be cross-compiling from a 32-bit platform to a 64-bit platform. 51 if test $fits_in_uint = 1; then 52 gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)" 53 else 54 gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)" 55 fi 56 else 57 dnl Shouldn't happen, but who knows... 58 gl_cv_size_max='((size_t)~(size_t)0)' 59 fi 60 fi 61 ]) 62 if test "$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 dnl Don't redefine SIZE_MAX in config.h if config.h is re-included after 67 dnl <stdint.h>. Remember that the #undef in AH_VERBATIM gets replaced with 68 dnl #define by AC_DEFINE_UNQUOTED. 69 AH_VERBATIM([SIZE_MAX], 70 [/* Define as the maximum value of type 'size_t', if the system doesn't define 71 it. */ 72 #ifndef SIZE_MAX 73 # undef SIZE_MAX 74 #endif]) 75 ])