infinite loop translating bizarre compound

[mk270]

The word "bestiasviginti" gets WORDS into an infinite loop, apparently.

[ids1024]

It seems to be stuck in this loop.

It also seems to be an issue with Whitaker's last release as well, and not an issue we added.

[mk270]

Hmm, a loop whose termination condition is also the loop invariant ...

[ids1024]

Do you have any idea what this loop is meant to achieve? Clearly Jj was meant to be modified in the body of the loop; otherwise I'm not sure.

If not, it's probably best to comment out the loop and add a line FIXME Figure out what this was meant to do and fix it or similar. Clearly the loop is never being entered except in cases like this where it causes an infinite loop.

This specific word seems to parse fine with the loop removed.

[mk270]

The loop is apparently never entered during the test cases, which involve translating a very long, badly formatted chunk of the Aeneid. Therefore it's very much a corner case. It may be that other varieties of Latin, e.g., church Latin, mediaeval Latin or whatever, or some non-default configuration choices lead to triggering the bug, but my hunch is it's exposed by a weird condition only true for very un-Latin-like input.

My instinct here is that we should throw an informatively-worded exception admitting that it's an internal programming error, and fix the underlying bug later. That will get rid of the infinite loop behaviour in the short term, which is a problem for code which wraps WORDS, without covering up other misbehaviours that may be more serious.

[mk270]

Incidentally, @ids1024 , did you find the place it was failing with gdb, or some other tool?

[ids1024]

I used gdb. I just built words with debugging symbols, triggered the issue, and hit ctrl-c which stopped it and printed the line it was on.

[ids1024]

@mk270 Where did you come across this word anyway?

[mk270]

The CGI version of WORDS had got into a busy loop, and the offending word was in its argv, and in the HTTP logs. There ensued some paranoid speculation about how on earth anyone had found such a word. It turns out to be a cut-n-paste error from some online Latin course.

[mk270]

I have a trivial patch which throws a bespoke exception.