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Member "xdelta3-3.0.11/m4/ax_check_aligned_access_required.m4" (24 Mar 2015, 3231 Bytes) of package /linux/misc/xdelta3-3.0.11.tar.gz:

    1 # ====================================================================================
    2 #  http://www.gnu.org/software/autoconf-archive/ax_check_aligned_access_required.html
    3 # ====================================================================================
    4 #
    5 # SYNOPSIS
    6 #
    7 #   AC_CHECK_ALIGNED_ACCESS_REQUIRED
    8 #
    9 # DESCRIPTION
   10 #
   11 #   While the x86 CPUs allow access to memory objects to be unaligned it
   12 #   happens that most of the modern designs require objects to be aligned -
   13 #   or they will fail with a buserror. That mode is quite known by
   14 #   big-endian machines (sparc, etc) however the alpha cpu is little-
   15 #   endian.
   16 #
   17 #   The following function will test for aligned access to be required and
   18 #   set a config.h define HAVE_ALIGNED_ACCESS_REQUIRED (name derived by
   19 #   standard usage). Structures loaded from a file (or mmapped to memory)
   20 #   should be accessed per-byte in that case to avoid segfault type errors.
   21 #
   22 # LICENSE
   23 #
   24 #   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
   25 #
   26 #   This program is free software; you can redistribute it and/or modify it
   27 #   under the terms of the GNU General Public License as published by the
   28 #   Free Software Foundation; either version 3 of the License, or (at your
   29 #   option) any later version.
   30 #
   31 #   This program is distributed in the hope that it will be useful, but
   32 #   WITHOUT ANY WARRANTY; without even the implied warranty of
   33 #   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
   34 #   Public License for more details.
   35 #
   36 #   You should have received a copy of the GNU General Public License along
   37 #   with this program. If not, see <http://www.gnu.org/licenses/>.
   38 #
   39 #   As a special exception, the respective Autoconf Macro's copyright owner
   40 #   gives unlimited permission to copy, distribute and modify the configure
   41 #   scripts that are the output of Autoconf when processing the Macro. You
   42 #   need not follow the terms of the GNU General Public License when using
   43 #   or distributing such scripts, even though portions of the text of the
   44 #   Macro appear in them. The GNU General Public License (GPL) does govern
   45 #   all other use of the material that constitutes the Autoconf Macro.
   46 #
   47 #   This special exception to the GPL applies to versions of the Autoconf
   48 #   Macro released by the Autoconf Archive. When you make and distribute a
   49 #   modified version of the Autoconf Macro, you may extend this special
   50 #   exception to the GPL to apply to your modified version as well.
   51 
   52 #serial 7
   53 
   54 AC_DEFUN([AX_CHECK_ALIGNED_ACCESS_REQUIRED],
   55 [AC_CACHE_CHECK([if pointers to integers require aligned access],
   56   [ax_cv_have_aligned_access_required],
   57   [AC_TRY_RUN([
   58 #include <stdio.h>
   59 #include <stdlib.h>
   60 
   61 int main()
   62 {
   63   char* string = malloc(40);
   64   int i;
   65   for (i=0; i < 40; i++) string[[i]] = i;
   66   {
   67      void* s = string;
   68      int* p = s+1;
   69      int* q = s+2;
   70 
   71      if (*p == *q) { return 1; }
   72   }
   73   return 0;
   74 }
   75               ],
   76      [ax_cv_have_aligned_access_required=yes],
   77      [ax_cv_have_aligned_access_required=no],
   78      [ax_cv_have_aligned_access_required=no])
   79   ])
   80 if test "$ax_cv_have_aligned_access_required" = yes ; then
   81   AC_DEFINE([HAVE_ALIGNED_ACCESS_REQUIRED], [1],
   82     [Define if pointers to integers require aligned access])
   83 fi
   84 ])