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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.
#
# LAST MODIFICATION
#
# 2006-08-17
#
# COPYLEFT
#
# Copyright (c) 2006 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, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
# 02111-1307, USA.
#
# 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 Macro 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=no],
[ax_cv_have_aligned_access_required=yes],
[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
])
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