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[libguestfs.git] / m4 / size_max.m4

diff --git a/m4/size_max.m4 b/m4/size_max.m4
index 6cb4868..5762fc3 100644 (file)
--- a/m4/size_max.m4
+++ b/m4/size_max.m4
@@ -1,8 +1,10 @@
-# size_max.m4 serial 6
-dnl Copyright (C) 2003, 2005-2006 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.
+# size_max.m4 serial 2
+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.
 
@@ -11,9 +13,8 @@ AC_DEFUN([gl_SIZE_MAX],
   AC_CHECK_HEADERS(stdint.h)
   dnl First test whether the system already has SIZE_MAX.
   AC_MSG_CHECKING([for SIZE_MAX])
-  AC_CACHE_VAL([gl_cv_size_max], [
-    gl_cv_size_max=
-    AC_EGREP_CPP([Found it], [
+  result=
+  AC_EGREP_CPP([Found it], [
 #include <limits.h>
 #if HAVE_STDINT_H
 #include <stdint.h>
@@ -21,48 +22,40 @@ AC_DEFUN([gl_SIZE_MAX],
 #ifdef SIZE_MAX
 Found it
 #endif
-], gl_cv_size_max=yes)
-    if test -z "$gl_cv_size_max"; then
-      dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
-      dnl than the type 'unsigned long'. Try hard to find a definition that can
-      dnl be used in a preprocessor #if, i.e. doesn't contain a cast.
-      AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1],
-        [#include <stddef.h>
-#include <limits.h>], size_t_bits_minus_1=)
-      AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)],
-        [#include <stddef.h>], fits_in_uint=)
-      if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then
-        if test $fits_in_uint = 1; then
-          dnl Even though SIZE_MAX fits in an unsigned int, it must be of type
-          dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'.
-          AC_TRY_COMPILE([#include <stddef.h>
-            extern size_t foo;
-            extern unsigned long foo;
-            ], [], fits_in_uint=0)
-        fi
-        dnl We cannot use 'expr' to simplify this expression, because 'expr'
-        dnl works only with 'long' integers in the host environment, while we
-        dnl might be cross-compiling from a 32-bit platform to a 64-bit platform.
-        if test $fits_in_uint = 1; then
-          gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)"
-        else
-          gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)"
-        fi
+], result=yes)
+  if test -z "$result"; then
+    dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
+    dnl than the type 'unsigned 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([~(size_t)0 / 10], res_hi,
+      [#include <stddef.h>], result=?)
+    _AC_COMPUTE_INT([~(size_t)0 % 10], res_lo,
+      [#include <stddef.h>], result=?)
+    _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint,
+      [#include <stddef.h>], result=?)
+    if test "$fits_in_uint" = 1; then
+      dnl Even though SIZE_MAX fits in an unsigned int, it must be of type
+      dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'.
+      AC_TRY_COMPILE([#include <stddef.h>
+        extern size_t foo;
+        extern unsigned long foo;
+        ], [], fits_in_uint=0)
+    fi
+    if test -z "$result"; then
+      if test "$fits_in_uint" = 1; then
+        result="$res_hi$res_lo"U
       else
-        dnl Shouldn't happen, but who knows...
-        gl_cv_size_max='((size_t)~(size_t)0)'
+        result="$res_hi$res_lo"UL
       fi
+    else
+      dnl Shouldn't happen, but who knows...
+      result='~(size_t)0'
     fi
-  ])
-  AC_MSG_RESULT([$gl_cv_size_max])
-  if test "$gl_cv_size_max" != yes; then
-    AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max],
+  fi
+  AC_MSG_RESULT([$result])
+  if test "$result" != yes; then
+    AC_DEFINE_UNQUOTED([SIZE_MAX], [$result],
       [Define as the maximum value of type 'size_t', if the system doesn't define it.])
   fi
 ])
-
-dnl Autoconf >= 2.61 has AC_COMPUTE_INT built-in.
-dnl Remove this when we can assume autoconf >= 2.61.
-m4_ifdef([AC_COMPUTE_INT], [], [
-  AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])])
-])