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longlong: tune, particularly for common case of c99 * m4/longlong.m4 (AC_TYPE_LONG_LONG_INT): Don't bother compiling or running anything if c99, or if unsigned long long int does not work. In either case, we know the answer without further tests. Do not compile _AC_TYPE_LONG_LONG_SNIPPET twice. Instead, compile it at most once, and use its results for both long long int and unsigned long long int. This is more likely to be efficient in the common case where the program wants to check for both long long int and unsigned long long int. (AC_TYPE_UNSIGNED_LONG_LONG_INT): Don't bother compiling if c99, since the answer is already known.
author Paul Eggert <eggert@cs.ucla.edu>
date Wed, 16 Feb 2011 01:22:38 -0800
parents 97fc9a21a8fb
children 4da22ca0951d
line wrap: on
line source

# longlong.m4 serial 15
dnl Copyright (C) 1999-2007, 2009-2011 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

dnl From Paul Eggert.

# Define HAVE_LONG_LONG_INT if 'long long int' works.
# This fixes a bug in Autoconf 2.61, and can be faster
# than what's in Autoconf 2.62 through 2.68.

# Note: If the type 'long long int' exists but is only 32 bits large
# (as on some very old compilers), HAVE_LONG_LONG_INT will not be
# defined. In this case you can treat 'long long int' like 'long int'.

AC_DEFUN([AC_TYPE_LONG_LONG_INT],
[
  AC_REQUIRE([AC_TYPE_UNSIGNED_LONG_LONG_INT])
  AC_CACHE_CHECK([for long long int], [ac_cv_type_long_long_int],
     [ac_cv_type_long_long_int=yes
      if test "x${ac_cv_prog_cc_c99-no}" = xno; then
        ac_cv_type_long_long_int=$ac_cv_type_unsigned_long_long_int
        if test $ac_cv_type_long_long_int = yes; then
          dnl Catch a bug in Tandem NonStop Kernel (OSS) cc -O circa 2004.
          dnl If cross compiling, assume the bug is not important, since
          dnl nobody cross compiles for this platform as far as we know.
          AC_RUN_IFELSE(
            [AC_LANG_PROGRAM(
               [[@%:@include <limits.h>
                 @%:@ifndef LLONG_MAX
                 @%:@ define HALF \
                          (1LL << (sizeof (long long int) * CHAR_BIT - 2))
                 @%:@ define LLONG_MAX (HALF - 1 + HALF)
                 @%:@endif]],
               [[long long int n = 1;
                 int i;
                 for (i = 0; ; i++)
                   {
                     long long int m = n << i;
                     if (m >> i != n)
                       return 1;
                     if (LLONG_MAX / 2 < m)
                       break;
                   }
                 return 0;]])],
            [],
            [ac_cv_type_long_long_int=no])
        fi
      fi])
  if test $ac_cv_type_long_long_int = yes; then
    AC_DEFINE([HAVE_LONG_LONG_INT], [1],
      [Define to 1 if the system has the type `long long int'.])
  fi
])

# Define HAVE_UNSIGNED_LONG_LONG_INT if 'unsigned long long int' works.
# This fixes a bug in Autoconf 2.61, and can be faster
# than what's in Autoconf 2.62 through 2.68.

# Note: If the type 'unsigned long long int' exists but is only 32 bits
# large (as on some very old compilers), AC_TYPE_UNSIGNED_LONG_LONG_INT
# will not be defined. In this case you can treat 'unsigned long long int'
# like 'unsigned long int'.

AC_DEFUN([AC_TYPE_UNSIGNED_LONG_LONG_INT],
[
  AC_CACHE_CHECK([for unsigned long long int],
    [ac_cv_type_unsigned_long_long_int],
    [ac_cv_type_unsigned_long_long_int=yes
     if test "x${ac_cv_prog_cc_c99-no}" = xno; then
       AC_LINK_IFELSE(
         [_AC_TYPE_LONG_LONG_SNIPPET],
         [],
         [ac_cv_type_unsigned_long_long_int=no])
     fi])
  if test $ac_cv_type_unsigned_long_long_int = yes; then
    AC_DEFINE([HAVE_UNSIGNED_LONG_LONG_INT], [1],
      [Define to 1 if the system has the type `unsigned long long int'.])
  fi
])

# Expands to a C program that can be used to test for simultaneous support
# of 'long long' and 'unsigned long long'. We don't want to say that
# 'long long' is available if 'unsigned long long' is not, or vice versa,
# because too many programs rely on the symmetry between signed and unsigned
# integer types (excluding 'bool').
AC_DEFUN([_AC_TYPE_LONG_LONG_SNIPPET],
[
  AC_LANG_PROGRAM(
    [[/* For now, do not test the preprocessor; as of 2007 there are too many
         implementations with broken preprocessors.  Perhaps this can
         be revisited in 2012.  In the meantime, code should not expect
         #if to work with literals wider than 32 bits.  */
      /* Test literals.  */
      long long int ll = 9223372036854775807ll;
      long long int nll = -9223372036854775807LL;
      unsigned long long int ull = 18446744073709551615ULL;
      /* Test constant expressions.   */
      typedef int a[((-9223372036854775807LL < 0 && 0 < 9223372036854775807ll)
                     ? 1 : -1)];
      typedef int b[(18446744073709551615ULL <= (unsigned long long int) -1
                     ? 1 : -1)];
      int i = 63;]],
    [[/* Test availability of runtime routines for shift and division.  */
      long long int llmax = 9223372036854775807ll;
      unsigned long long int ullmax = 18446744073709551615ull;
      return ((ll << 63) | (ll >> 63) | (ll < i) | (ll > i)
              | (llmax / ll) | (llmax % ll)
              | (ull << 63) | (ull >> 63) | (ull << i) | (ull >> i)
              | (ullmax / ull) | (ullmax % ull));]])
])