85 lines
3.2 KiB
Text
85 lines
3.2 KiB
Text
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# ====================================================================================
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# http://www.gnu.org/software/autoconf-archive/ax_check_aligned_access_required.html
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# ====================================================================================
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#
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# SYNOPSIS
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#
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# AC_CHECK_ALIGNED_ACCESS_REQUIRED
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#
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# DESCRIPTION
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#
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# While the x86 CPUs allow access to memory objects to be unaligned it
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# happens that most of the modern designs require objects to be aligned -
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# or they will fail with a buserror. That mode is quite known by
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# big-endian machines (sparc, etc) however the alpha cpu is little-
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# endian.
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#
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# The following function will test for aligned access to be required and
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# set a config.h define HAVE_ALIGNED_ACCESS_REQUIRED (name derived by
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# standard usage). Structures loaded from a file (or mmapped to memory)
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# should be accessed per-byte in that case to avoid segfault type errors.
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#
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# LICENSE
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#
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# Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
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#
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# This program is free software; you can redistribute it and/or modify it
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# under the terms of the GNU General Public License as published by the
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# Free Software Foundation; either version 3 of the License, or (at your
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# option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
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# Public License for more details.
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#
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# You should have received a copy of the GNU General Public License along
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# with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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# As a special exception, the respective Autoconf Macro's copyright owner
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# gives unlimited permission to copy, distribute and modify the configure
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# scripts that are the output of Autoconf when processing the Macro. You
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# need not follow the terms of the GNU General Public License when using
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# or distributing such scripts, even though portions of the text of the
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# Macro appear in them. The GNU General Public License (GPL) does govern
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# all other use of the material that constitutes the Autoconf Macro.
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#
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# This special exception to the GPL applies to versions of the Autoconf
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# Macro released by the Autoconf Archive. When you make and distribute a
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# modified version of the Autoconf Macro, you may extend this special
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# exception to the GPL to apply to your modified version as well.
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#serial 7
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AC_DEFUN([AX_CHECK_ALIGNED_ACCESS_REQUIRED],
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[AC_CACHE_CHECK([if pointers to integers require aligned access],
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[ax_cv_have_aligned_access_required],
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[AC_TRY_RUN([
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#include <stdio.h>
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#include <stdlib.h>
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int main()
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{
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char* string = malloc(40);
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int i;
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for (i=0; i < 40; i++) string[[i]] = i;
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{
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void* s = string;
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int* p = s+1;
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int* q = s+2;
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if (*p == *q) { return 1; }
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}
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return 0;
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}
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],
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[ax_cv_have_aligned_access_required=yes],
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[ax_cv_have_aligned_access_required=no],
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[ax_cv_have_aligned_access_required=no])
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])
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if test "$ax_cv_have_aligned_access_required" = yes ; then
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AC_DEFINE([HAVE_ALIGNED_ACCESS_REQUIRED], [1],
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[Define if pointers to integers require aligned access])
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fi
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])
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