# size_max.m4 serial 11

dnl Copyright (C) 2003, 2005-2006, 2008-2020 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=

    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_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])

])