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Annotation of embedaddon/confuse/m4/size_max.m4, revision 1.1.1.1

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: ])