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Annotation of embedaddon/confuse/m4/size_max.m4, revision 1.1

1.1     ! misho       1: # size_max.m4 serial 5
        !             2: dnl Copyright (C) 2003, 2005-2006 Free Software Foundation, Inc.
        !             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: [
        !            11:   AC_CHECK_HEADERS(stdint.h)
        !            12:   dnl First test whether the system already has SIZE_MAX.
        !            13:   AC_MSG_CHECKING([for SIZE_MAX])
        !            14:   AC_CACHE_VAL([gl_cv_size_max], [
        !            15:     gl_cv_size_max=
        !            16:     AC_EGREP_CPP([Found it], [
        !            17: #include <limits.h>
        !            18: #if HAVE_STDINT_H
        !            19: #include <stdint.h>
        !            20: #endif
        !            21: #ifdef SIZE_MAX
        !            22: Found it
        !            23: #endif
        !            24: ], gl_cv_size_max=yes)
        !            25:     if test -z "$gl_cv_size_max"; then
        !            26:       dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
        !            27:       dnl than the type 'unsigned long'. Try hard to find a definition that can
        !            28:       dnl be used in a preprocessor #if, i.e. doesn't contain a cast.
        !            29:       _AC_COMPUTE_INT([sizeof (size_t) * CHAR_BIT - 1], size_t_bits_minus_1,
        !            30:         [#include <stddef.h>
        !            31: #include <limits.h>], size_t_bits_minus_1=)
        !            32:       _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint,
        !            33:         [#include <stddef.h>], fits_in_uint=)
        !            34:       if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then
        !            35:         if test $fits_in_uint = 1; then
        !            36:           dnl Even though SIZE_MAX fits in an unsigned int, it must be of type
        !            37:           dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'.
        !            38:           AC_TRY_COMPILE([#include <stddef.h>
        !            39:             extern size_t foo;
        !            40:             extern unsigned long foo;
        !            41:             ], [], fits_in_uint=0)
        !            42:         fi
        !            43:         dnl We cannot use 'expr' to simplify this expression, because 'expr'
        !            44:         dnl works only with 'long' integers in the host environment, while we
        !            45:         dnl might be cross-compiling from a 32-bit platform to a 64-bit platform.
        !            46:         if test $fits_in_uint = 1; then
        !            47:           gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)"
        !            48:         else
        !            49:           gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)"
        !            50:         fi
        !            51:       else
        !            52:         dnl Shouldn't happen, but who knows...
        !            53:         gl_cv_size_max='((size_t)~(size_t)0)'
        !            54:       fi
        !            55:     fi
        !            56:   ])
        !            57:   AC_MSG_RESULT([$gl_cv_size_max])
        !            58:   if test "$gl_cv_size_max" != yes; then
        !            59:     AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max],
        !            60:       [Define as the maximum value of type 'size_t', if the system doesn't define it.])
        !            61:   fi
        !            62: ])