Bug#630441: g++-4.6 miscompilation

[Matthias Klose <doko@debian.org>]

On 07/21/2011 02:26 AM, Philip Ashmore wrote:
> This fails with g++-4.6.1-4 from testing at the same place.
> 
> I've updated the packages in sourceforge, so no patches are needed.
> I've attached a revised build.sh which runs the tests with the
> current versions.
> 
> I was about to dive into a rant about "why didn't you try this before
> releasing gcc/g++ 4.6.1-4" when I spotted a bug in v3c's build system,
> now fixed.
> 
> If you'd tried it yourself you could have let me know.
> Shouldn't incorrect code generation block a compiler release?

how do you know that it's not undefined behaviour exposed by the new compiler
version?

Some more information is needed:

 - is this seen on amd64 only, or on other architectures too?
 - which optimization flags are used? does lowering the optimization
   level works around the issue?
 - does it build using gcc-snapshot, gcc-4.5 or gcc-4.4?
 - if you have a working and a non-working build, can you try
   to combine object files to determine the problematice object
   file?