align32.c

/*
 * align32 - determine if 32 bit accesses must be aligned
 *
 * Copyright (C) 1999,2021  Landon Curt Noll
 *
 * Calc is open software; you can redistribute it and/or modify it under
 * the terms of the version 2.1 of the GNU Lesser General Public License
 * as published by the Free Software Foundation.
 *
 * Calc 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 Lesser General
 * Public License for more details.
 *
 * A copy of version 2.1 of the GNU Lesser General Public License is
 * distributed with calc under the filename COPYING-LGPL.  You should have
 * received a copy with calc; if not, write to Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * Under source code control:   1995/11/23 05:18:06
 * File existed as early as:    1995
 *
 * chongo <was here> /\oo/\     http://www.isthe.com/chongo/
 * Share and enjoy!  :-)        http://www.isthe.com/chongo/tech/comp/calc/
 */


#include <stdio.h>
#include <signal.h>
#include "have_stdlib.h"
#if defined(HAVE_STDLIB_H)
#include <stdlib.h>
#endif

#include "longbits.h"

#include "have_unistd.h"
#if defined(HAVE_UNISTD_H)
#include <unistd.h>
#endif

#include "have_unused.h"


#include "banned.h"     /* include after system header <> includes */


static void buserr(int arg);    /* catch alignment errors */


int
main(void)
{
        char byte[2*sizeof(USB32)];     /* mis-alignment buffer */
        USB32 *p;                       /* mis-alignment pointer */
        unsigned long i;

#if defined(MUST_ALIGN32)
        /* force alignment */
        printf("#define MUST_ALIGN32\t%c* forced to align 32 bit values *%c\n",
           '/', '/');
#else
        /* setup to catch alignment bus errors */
        signal(SIGBUS, buserr);
        signal(SIGSEGV, buserr);  /* some systems will generate SEGV instead! */

        /* mis-align our long fetches */
        for (i=0; i < sizeof(USB32); ++i) {
                p = (USB32 *)(byte+i);
                *p = i;
                *p += 1;
        }

        /* if we got here, then we can mis-align longs */
        printf("#undef MUST_ALIGN32\t%c* can mis-align 32 bit values *%c\n",
           '/', '/');

#endif
        /* exit(0); */
        return 0;
}


/*
 * buserr - catch an alignment error
 *
 * given:
 *      arg             to keep ANSI C happy
 */
/*ARGSUSED*/
static void
buserr(int UNUSED(arg))
{
        /* alignment is required */
        printf("#define MUST_ALIGN32\t%c* must align 32 bit values *%c\n",
          '/', '/');
        exit(0);
}