How to invoke the help function with optparse-c

Question

I am trying to use the optparse-c library. This library seems to me quite useful. What I find not so clear is how to invoke the help without calling prog -h. I can do it if I remove the keyword static from the function signature static void printopts(FILE *f) in optparse.c, then I could do:

int main(int argc, char **argv)
{
    int i;

    opt_basename(argv[0], '/');
    if (opt_parse("usage: %s [options] arg1 arg2", options, argv) != 2) {
        printopts(stderr);

        exit(EXIT_FAILURE);
    }
    ...

However, it seems to me the author of this library had some other idea how to invoke the help function. I would be happy if someone could help me figure this out.

I also tried this:

char h[] = "-h";
opt_basename(argv[0], '/');
if (opt_parse("usage: %s [options] arg1 arg2", options, argv) != 2) {
    argc++;
    strcpy(argv[1], h);
    opt_parse("usage: %s [options] arg1 arg2", options, argv);

    exit(EXIT_FAILURE);
}

Answer 1

Oh well, after a lot of poking and looking into the source code, I found out the not trivial (as I am still learning C) solution:

if (opt_parse("usage: %s [options] arg1 arg2", options, argv) != 2) {

        opt_help(0, (void *)0);

        exit(EXIT_FAILURE);
    }