kc3-lang/gnulib/m4/ptrdiff_max.m4

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• Hash : 5ef49441
  Author :
  Date : 2003-11-11T11:57:04
  

  Macro for determining PTRDIFF_MAX.
  

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• m4/ptrdiff_max.m4

• # ptrdiff_max.m4 serial 1
  dnl Copyright (C) 2003 Free Software Foundation, Inc.
  dnl This file is free software, distributed under the terms of the GNU
  dnl General Public License.  As a special exception to the GNU General
  dnl Public License, this file may be distributed as part of a program
  dnl that contains a configuration script generated by Autoconf, under
  dnl the same distribution terms as the rest of that program.
  
  dnl From Bruno Haible.
  
  AC_DEFUN([gl_PTRDIFF_MAX],
  [
    AC_CHECK_TYPE([ptrdiff_t], ,
      [AC_DEFINE([ptrdiff_t], [long],
         [Define as the type of the result of subtracting two pointers, if the system doesn't define it.])
      ])
    AC_CHECK_HEADERS_ONCE(stdint.h)
    dnl First test whether the system already has PTRDIFF_MAX.
    AC_MSG_CHECKING([for PTRDIFF_MAX])
    result=
    AC_EGREP_CPP([Found it], [
  #include <limits.h>
  #if HAVE_STDINT_H
  #include <stdint.h>
  #endif
  #ifdef PTRDIFF_MAX
  Found it
  #endif
  ], result=yes)
    if test -z "$result"; then
      dnl Define it ourselves. Here we assume that the type 'ptrdiff_t' is not
      dnl wider than the type 'long'.
      dnl The _AC_COMPUTE_INT macro works up to LONG_MAX, since it uses 'expr',
      dnl which is guaranteed to work from LONG_MIN to LONG_MAX.
      _AC_COMPUTE_INT([STYPE_MAXIMUM (ptrdiff_t)], res, [
  #include <stddef.h>
  #include <limits.h>
  #define STYPE_MINIMUM(t) (~ (t) 0 << (sizeof (t) * CHAR_BIT - 1))
  #define STYPE_MAXIMUM(t) ((t) (~ (t) 0 - STYPE_MINIMUM (t)))
  ], result=?)
      _AC_COMPUTE_INT([sizeof (ptrdiff_t) <= sizeof (int)], fits_in_int,
        [#include <stddef.h>], result=?)
      if test "$fits_in_int" = 1; then
        dnl Even though PTRDIFF_MAX fits in an int, it must be of type
        dnl 'long' if the type 'ptrdiff_t' is the same as 'long'.
        AC_TRY_COMPILE([#include <stddef.h>
          extern ptrdiff_t foo;
          extern long foo;
          ], [], fits_in_int=0)
      fi
      if test -z "$result"; then
        if test "$fits_in_int" = 1; then
          result="$res"
        else
          result="$res"L
        fi
      else
        dnl Shouldn't happen, but who knows...
        result='((ptrdiff_t)(~(ptrdiff_t)0-(~(ptrdiff_t)0<<(sizeof(ptrdiff_t)*CHAR_BIT-1))))'
      fi
    fi
    AC_MSG_RESULT([$result])
    if test "$result" != yes; then
      AC_DEFINE_UNQUOTED([PTRDIFF_MAX], [$result],
        [Define as the maximum value of type 'ptrdiff_t', if the system doesn't define it.])
    fi
  ])
  

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