I've stumbled across a _very_ obscure procedure that produces non-functional mozillas. You need all three if gcc 2.95.3, -O and -DDEBUG to reproduce it. These bugzilla text boxes are way too small so read the attachment.
Obscure compiler bugs are nice to know about but I fail to see how this can be considered a Mozilla bug. At a glance, there doesn't seem to be anything wrong with that particular snippet of code. I would suggest submitting the bug to the gcc team and/or trying a newer version of gcc to see if it fixes the problem.
Well, mozilla has been known to alter code to work around other compiler bugs. Maybe it should here as well. It would be nice if this made it into some documentations some where. It would be even nicer if configure would warn about compiler and option configurations known to be buggy.