unionfs over cd9660 - solved (?)

hi,

I've reported (at least twice) a problem with mounting unionfs over
cd9660 as the underlying device, that seemed to appear in 7.0-BETA2 or
7.0-BETA3. I've received no independent confirmation of the problems or
ideas why it would occur, so I kept trying to solve it when I got time.

At last I I've narrowed it down to a strange conclusion: it appears the
problem was connected somehow to my build machine, i.e. it's probably
not in the code itself. After unsuccessfully trying various dates for
cvsup times and similar things, I've created a clean machine as a last
resort, and the problem was gone! After comparing the two setups, the
most likely cause is a compiler bug when certain optimizations are
enabled. The old system had "-Os -mtune=generic", and based on previous
experience and reports on the mailing lists I believe the "-Os" part is
the most likely culprit. I'll try to verify this theory soon-ish.

This solves my problem but the mystery remains why the error condition
suddenly appeared at that specific time. Of course, with a buggy compiler
almost any change in the code could have provoked it, but still, the
rest of the system (and ports) compiled with the flags was working
perfectly fine.