isupper() core dump: also, gdb core dump

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

I've tried packaging Guitar (see wip/Guitar).  But when I run it, it
fails with

ctype(3) isupper: invalid input: -61

I tried running it in gdb, but then gdb hangs or dumps core too.

I looked at all isupper() uses in the Guitar tarball itself, but they
look fine, so I suspect one of the used libraries is unsafe or gets
passed invalid data, but I'm not sure how to investigate it further.

Does gdb work on this for anyone else?
Or can someone please fix gdb? :-)

That's on a 2025-06-24 10.99.14/x86_64.
 Thomas