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Annotation of embedaddon/confuse/m4/size_max.m4, revision 1.1.1.2

1.1.1.2 ! misho       1: # size_max.m4 serial 10
        !             2: dnl Copyright (C) 2003, 2005-2006, 2008-2013 Free Software Foundation, Inc.
1.1       misho       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_DEFUN([gl_SIZE_MAX],
                     10: [
1.1.1.2 ! misho      11:   AC_CHECK_HEADERS([stdint.h])
1.1       misho      12:   dnl First test whether the system already has SIZE_MAX.
1.1.1.2 ! misho      13:   AC_CACHE_CHECK([for SIZE_MAX], [gl_cv_size_max], [
1.1       misho      14:     gl_cv_size_max=
                     15:     AC_EGREP_CPP([Found it], [
                     16: #include <limits.h>
                     17: #if HAVE_STDINT_H
                     18: #include <stdint.h>
                     19: #endif
                     20: #ifdef SIZE_MAX
                     21: Found it
                     22: #endif
1.1.1.2 ! misho      23: ], [gl_cv_size_max=yes])
1.1       misho      24:     if test -z "$gl_cv_size_max"; then
                     25:       dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
                     26:       dnl than the type 'unsigned long'. Try hard to find a definition that can
                     27:       dnl be used in a preprocessor #if, i.e. doesn't contain a cast.
1.1.1.2 ! misho      28:       AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1],
1.1       misho      29:         [#include <stddef.h>
1.1.1.2 ! misho      30: #include <limits.h>], [size_t_bits_minus_1=])
        !            31:       AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)],
        !            32:         [#include <stddef.h>], [fits_in_uint=])
1.1       misho      33:       if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then
                     34:         if test $fits_in_uint = 1; then
                     35:           dnl Even though SIZE_MAX fits in an unsigned int, it must be of type
                     36:           dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'.
1.1.1.2 ! misho      37:           AC_COMPILE_IFELSE(
        !            38:             [AC_LANG_PROGRAM(
        !            39:                [[#include <stddef.h>
        !            40:                  extern size_t foo;
        !            41:                  extern unsigned long foo;
        !            42:                ]],
        !            43:                [[]])],
        !            44:             [fits_in_uint=0])
1.1       misho      45:         fi
                     46:         dnl We cannot use 'expr' to simplify this expression, because 'expr'
                     47:         dnl works only with 'long' integers in the host environment, while we
                     48:         dnl might be cross-compiling from a 32-bit platform to a 64-bit platform.
                     49:         if test $fits_in_uint = 1; then
                     50:           gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)"
                     51:         else
                     52:           gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)"
                     53:         fi
                     54:       else
                     55:         dnl Shouldn't happen, but who knows...
                     56:         gl_cv_size_max='((size_t)~(size_t)0)'
                     57:       fi
                     58:     fi
                     59:   ])
                     60:   if test "$gl_cv_size_max" != yes; then
                     61:     AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max],
                     62:       [Define as the maximum value of type 'size_t', if the system doesn't define it.])
                     63:   fi
1.1.1.2 ! misho      64:   dnl Don't redefine SIZE_MAX in config.h if config.h is re-included after
        !            65:   dnl <stdint.h>. Remember that the #undef in AH_VERBATIM gets replaced with
        !            66:   dnl #define by AC_DEFINE_UNQUOTED.
        !            67:   AH_VERBATIM([SIZE_MAX],
        !            68: [/* Define as the maximum value of type 'size_t', if the system doesn't define
        !            69:    it. */
        !            70: #ifndef SIZE_MAX
        !            71: # undef SIZE_MAX
        !            72: #endif])
        !            73: ])
        !            74: 
        !            75: dnl Autoconf >= 2.61 has AC_COMPUTE_INT built-in.
        !            76: dnl Remove this when we can assume autoconf >= 2.61.
        !            77: m4_ifdef([AC_COMPUTE_INT], [], [
        !            78:   AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])])
1.1       misho      79: ])