gistfile1.c

int catvars(char *buf1, char *buf2, unsigned int len1,
            unsigned int len2){
    char mybuf[256];

    if((len1 + len2) > 256){    /* [3] */
        return -1;
    }

    memcpy(mybuf, buf1, len1);      /* [4] */
    memcpy(mybuf + len1, buf2, len2);

    do_some_stuff(mybuf);

    return 0;
}