c_cpp/etc/calc/align32.c

   1 /*
   2  * align32 - determine if 32 bit accesses must be aligned
   3  *
   4  * Copyright (C) 1999  Landon Curt Noll
   5  *
   6  * Calc is open software; you can redistribute it and/or modify it under
   7  * the terms of the version 2.1 of the GNU Lesser General Public License
   8  * as published by the Free Software Foundation.
   9  *
  10  * Calc is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  12  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General
  13  * Public License for more details.
  14  *
  15  * A copy of version 2.1 of the GNU Lesser General Public License is
  16  * distributed with calc under the filename COPYING-LGPL.  You should have
  17  * received a copy with calc; if not, write to Free Software Foundation, Inc.
  18  * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  19  *
  20  * @(#) $Revision: 30.1 $
  21  * @(#) $Id: align32.c,v 30.1 2007/03/16 11:09:46 chongo Exp $
  22  * @(#) $Source: /usr/local/src/bin/calc/RCS/align32.c,v $
  23  *
  24  * Under source code control:   1995/11/23 05:18:06
  25  * File existed as early as:    1995
  26  *
  27  * chongo <was here> /\oo/\     http://www.isthe.com/chongo/
  28  * Share and enjoy!  :-)        http://www.isthe.com/chongo/tech/comp/calc/
  29  */
  30
  31
  32 #include <stdio.h>
  33 #include <signal.h>
  34 #include "longbits.h"
  35
  36 #include "have_unistd.h"
  37 #if defined(HAVE_UNISTD_H)
  38 #include <unistd.h>
  39 #endif
  40
  41 static void buserr(void);       /* catch alignment errors */
  42
  43
  44 int
  45 main(void)
  46 {
  47         char byte[2*sizeof(USB32)];     /* mis-alignment buffer */
  48         USB32 *p;                       /* mis-alignment pointer */
  49         int i;
  50
  51 #if defined(MUST_ALIGN32)
  52         /* force alignment */
  53         printf("#define MUST_ALIGN32\t%c* forced to align 32 bit values *%c\n",
  54            '/', '/');
  55 #else
  56         /* setup to catch alignment bus errors */
  57         signal(SIGBUS, buserr);
  58         signal(SIGSEGV, buserr);  /* some systems will generate SEGV instead! */
  59
  60         /* mis-align our long fetches */
  61         for (i=0; i < sizeof(USB32); ++i) {
  62                 p = (USB32 *)(byte+i);
  63                 *p = i;
  64                 *p += 1;
  65         }
  66
  67         /* if we got here, then we can mis-align longs */
  68         printf("#undef MUST_ALIGN32\t%c* can mis-align 32 bit values *%c\n",
  69            '/', '/');
  70
  71 #endif
  72         /* exit(0); */
  73         return 0;
  74 }
  75
  76
  77 /*
  78  * buserr - catch an alignment error
  79  *
  80  * given:
  81  *      arg             to keep ANSI C happy
  82  */
  83 /*ARGSUSED*/
  84 static void
  85 buserr(int arg)
  86 {
  87         /* alignment is required */
  88         printf("#define MUST_ALIGN32\t%c* must align 32 bit values *%c\n",
  89           '/', '/');
  90         exit(0);
  91 }