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# size_max.m4 serial 6
dnl Copyright (C) 2003, 2005-2006 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_DEFUN([gl_SIZE_MAX],
[
AC_CHECK_HEADERS(stdint.h)
dnl First test whether the system already has SIZE_MAX.
AC_MSG_CHECKING([for SIZE_MAX])
AC_CACHE_VAL([gl_cv_size_max], [
gl_cv_size_max=
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 -z "$gl_cv_size_max"; then
dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
dnl than the type 'unsigned long'. Try hard to find a definition that can
dnl be used in a preprocessor #if, i.e. doesn't contain a cast.
AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1],
[#include <stddef.h>
#include <limits.h>], size_t_bits_minus_1=)
AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)],
[#include <stddef.h>], fits_in_uint=)
if test -n "$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_TRY_COMPILE([#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 << $size_t_bits_minus_1) - 1) * 2 + 1)"
fi
else
dnl Shouldn't happen, but who knows...
gl_cv_size_max='((size_t)~(size_t)0)'
fi
fi
])
AC_MSG_RESULT([$gl_cv_size_max])
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 Autoconf >= 2.61 has AC_COMPUTE_INT built-in.
dnl Remove this when we can assume autoconf >= 2.61.
m4_ifdef([AC_COMPUTE_INT], [], [
AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])])
])
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