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confuse 2.7

    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: ])