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# size_max.m4 serial 12
dnl Copyright (C) 2003, 2005-2006, 2008-2021 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
dnl From Bruno Haible.
AC_PREREQ([2.61])
AC_DEFUN([gl_SIZE_MAX],
[
AC_CHECK_HEADERS([stdint.h])
dnl First test whether the system already has SIZE_MAX.
AC_CACHE_CHECK([for SIZE_MAX], [gl_cv_size_max], [
gl_cv_size_max=no
AC_EGREP_CPP([Found it], [
#include <limits.h>
#if HAVE_STDINT_H
#include <stdint.h>
#endif
#ifdef SIZE_MAX
Found it
#endif
], [gl_cv_size_max=yes])
if test $gl_cv_size_max != yes; then
dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
dnl than the type 'unsigned long'. Try hard to find a definition that can
dnl be used in a preprocessor #if, i.e. doesn't contain a cast.
AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1],
[#include <stddef.h>
#include <limits.h>], [size_t_bits_minus_1=])
AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)],
[#include <stddef.h>], [fits_in_uint=])
if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then
if test $fits_in_uint = 1; then
dnl Even though SIZE_MAX fits in an unsigned int, it must be of type
dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'.
AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM(
[[#include <stddef.h>
extern size_t foo;
extern unsigned long foo;
]],
[[]])],
[fits_in_uint=0])
fi
dnl We cannot use 'expr' to simplify this expression, because 'expr'
dnl works only with 'long' integers in the host environment, while we
dnl might be cross-compiling from a 32-bit platform to a 64-bit platform.
if test $fits_in_uint = 1; then
gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)"
else
gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)"
fi
else
dnl Shouldn't happen, but who knows...
gl_cv_size_max='((size_t)~(size_t)0)'
fi
fi
])
if test "$gl_cv_size_max" != yes; then
AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max],
[Define as the maximum value of type 'size_t', if the system doesn't define it.])
fi
dnl Don't redefine SIZE_MAX in config.h if config.h is re-included after
dnl <stdint.h>. Remember that the #undef in AH_VERBATIM gets replaced with
dnl #define by AC_DEFINE_UNQUOTED.
AH_VERBATIM([SIZE_MAX],
[/* Define as the maximum value of type 'size_t', if the system doesn't define
it. */
#ifndef SIZE_MAX
# undef SIZE_MAX
#endif])
])
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