imported http://git.cryp.to/autoconf-archive

Merge branch 'pre-savannah-history'

1 files changed, 82 insertions, 0 deletions

diff --git a/m4/ax_check_aligned_access_required.m4 b/m4/ax_check_aligned_access_required.m4
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+# ===========================================================================
+#    http://autoconf-archive.cryp.to/ax_check_aligned_access_required.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AC_CHECK_ALIGNED_ACCESS_REQUIRED
+#
+# DESCRIPTION
+#
+#   While the x86 CPUs allow access to memory objects to be unaligned it
+#   happens that most of the modern designs require objects to be aligned -
+#   or they will fail with a buserror. That mode is quite known by
+#   big-endian machines (sparc, etc) however the alpha cpu is little-
+#   endian.
+#
+#   The following function will test for aligned access to be required and
+#   set a config.h define HAVE_ALIGNED_ACCESS_REQUIRED (name derived by
+#   standard usage). Structures loaded from a file (or mmapped to memory)
+#   should be accessed per-byte in that case to avoid segfault type errors.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
+#
+#   This program is free software; you can redistribute it and/or modify it
+#   under the terms of the GNU General Public License as published by the
+#   Free Software Foundation; either version 2 of the License, or (at your
+#   option) any later version.
+#
+#   This program is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+#   Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License along
+#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+AC_DEFUN([AX_CHECK_ALIGNED_ACCESS_REQUIRED],
+[AC_CACHE_CHECK([if pointers to integers require aligned access],
+  [ax_cv_have_aligned_access_required],
+  [AC_TRY_RUN([
+#include <stdio.h>
+#include <stdlib.h>
+
+int main()
+{
+  char* string = malloc(40);
+  int i;
+  for (i=0; i < 40; i++) string[[i]] = i;
+  {
+     void* s = string;
+     int* p = s+1;
+     int* q = s+2;
+
+     if (*p == *q) { return 1; }
+  }
+  return 0;
+}
+              ],
+     [ax_cv_have_aligned_access_required=yes],
+     [ax_cv_have_aligned_access_required=no],
+     [ax_cv_have_aligned_access_required=no])
+  ])
+if test "$ax_cv_have_aligned_access_required" = yes ; then
+  AC_DEFINE([HAVE_ALIGNED_ACCESS_REQUIRED], [1],
+    [Define if pointers to integers require aligned access])
+fi
+])