Use of " ? : " in format param to printf

[Robert Seals]

I have a question.

main()
{
    double sum;
    int count;

    /* ..... */

    printf(count == 0 ? " ---- " : " %4.0lf ", sum / count);
}

(If something is dopey, just ignore it because the main thing is...)

Does it matter if there are unused arguments to printf? That is, if
'count' is zero, will anything be screwed up because there is extra
crud in the code? The actual application I'm doing is much more
complicated than this (REALLY??), but the principal is the same.
Is this OK code? Lint didn't mind, nor did gcc -Wall.

rob