Jeff King [off-list ref] writes:

  int my_foo;
  ...
  OPT_CALLBACK('f', "foo", int, &my_foo, ...etc);

Not great, but it might not be _too_ bad given that most helpers like
OPT_BOOL() can just say "int" behind the scenes.

That said, I don't recall these void pointers being a large source of
errors in the past. So while it's a fun type-system puzzle, the
effort/reward ratio might not be favorable.

I tend to agree on both counts, it is a fun puzzle, and it probably
is not going to give us sufficient reward.  The fact that "int" and
typeof(my_foo) need to be manually kept straight defeats the "type
safety" justification for this mental exercise.

Thanks.