extern void abort(void);
extern void exit(int);

void foo(char *bp, unsigned n) {
    register char c;
    register char *ep = bp + n;
    register char *sp;

    while (bp < ep) {
        sp = bp + 3;
        c = *sp;
        *sp = *bp;
        *bp++ = c;
        sp = bp + 1;
        c = *sp;
        *sp = *bp;
        *bp++ = c;
        bp += 2;
    }
}

int main(void) {
    int one = 1;

    if (sizeof(int) != 4 * sizeof(char))
        exit(0);

    foo((char *)&one, sizeof(one));
    foo((char *)&one, sizeof(one));

    if (one != 1)
        abort();

    exit(0);
}
