inf-inf evaluates to 0. Should be indeterminate
Sadly, this isn't particularly easy to fix. There's a much more comprehensive bug report at [#988], which contains more information about the problem.
I'm closing this report as a duplicate of that one. Unfortunately, SourceForge's bug tracker doesn't understand complicated things like duplicate bugs (sigh), so I have to mark this as wont-fix. Here's hoping that's incorrect... :-)