Report described this as a panic triggered by the sanity_check
option, but that's because it was running under the fuzzer, which
escalates any impossible() to panic(), rather than because nethack
panicked.
I couldn't find anything wrong--which doesn't mean that there
isn't something wrong--with place_worm_tail_randomly() and
random_dir(). They use xchar for map coordinates which should be
fine as long as no negative values are generated and I couldn't
discover any such. The suggested fix of changing xchar to int
might indicate a compiler bug (although the odds of that are low).
The bogus coordinate of -15000 in the report suggests that
typedef short int schar;
(which changes xchar too) is being used in the configuration but
I don't recall having any problems attributable to that.
This switches from xchar to int as a side-effect of replacing the
offending code entirely. The new code might produce an 'ny' of -1
before goodpos() rejects it, so xchar would be inappropriate now.
The old code is commented out via #if 0 _after_ changing it from
xchar to int.
This also adds an extra sanity_check for worm tails, unrelated to
the current bug. I'm not aware of any instance where it fails.
EXTRA_SANITY_CHECKS needs to be defined for it to do anything.
a48b4aa8ba