# size_max.m4 serial 4

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])

  result=

  AC_EGREP_CPP([Found it], [

#include <limits.h>

#if HAVE_STDINT_H

#include <stdint.h>

#endif

#ifdef SIZE_MAX

Found it

#endif

], result=yes)

  if test -z "$result"; 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([sizeof (size_t) * CHAR_BIT - 1], size_t_bits_minus_1,

      [#include <stddef.h>

#include <limits.h>], size_t_bits_minus_1=)

    _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint,

      [#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

        result="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)"

      else

        result="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)"

      fi

    else

      dnl Shouldn't happen, but who knows...

      result='((size_t)~(size_t)0)'

    fi

  fi

  AC_MSG_RESULT([$result])

  if test "$result" != yes; then

    AC_DEFINE_UNQUOTED([SIZE_MAX], [$result],

      [Define as the maximum value of type 'size_t', if the system doesn't define it.])

  fi

])