Function tabexpand

src/hacklib.c:428–464

expand tabs into proper number of spaces (in place) */

/* expand tabs into proper number of spaces (in place) */
char *
tabexpand(
    char *sbuf) /* assumed to be [BUFSZ] but can be smaller provided that
                 * expanded string fits; expansion bigger than BUFSZ-1
                 * will be truncated */
{
    char buf[BUFSZ + 10];
    char *bp, *s = sbuf;
    int idx;

    if (!*s)
        return sbuf;
    for (bp = buf, idx = 0; *s; s++) {
        if (*s == '\t') {
            /*
             * clang-8's optimizer at -Os has been observed to mis-compile
             * this code.  Symptom is nethack getting stuck in an apparent
             * infinite loop (or perhaps just an extremely long one) when
             * examining data.base entries.
             * clang-9 doesn't exhibit this problem.  [Was the incorrect
             * optimization fixed or just disabled?]
             */
            do
                *bp++ = ' ';
            while (++idx % 8);
        } else {
            *bp++ = *s;
            ++idx;
        }
        if (idx >= BUFSZ) {
            bp = &buf[BUFSZ - 1];
            break;
        }
    }
    *bp = 0;
    return strcpy(sbuf, buf);
}

#define VISCTRL_NBUF 5
/* make a displayable string from a character */