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Re: defaulting to GCC-4.7 for kfreebsd

2012/5/5 Christoph Egger <christoph@debian.org>:
>> I tried anyway with gcc-4.7, and src:kfreebsd-9 successfully built a
>> kfreebsd-i386 kernel that seems stable for a few days now.  Also the
>> freebsd-utils (essential stuff for kfreebsd-* arches) were okay.
>  This is, however good to know. Good thing to have the possibility to
> build kernel and "rest" of the archive with the same compiler.
>> I guess upstream has spent a lot of time already fixing up code for
>> Clang/LLVM, which might reduce the impact of switching to gcc-4.7.
>  This also tells us we might consider using clang for kernel and
> freebsd-* post wheezy to be consistent with upstream here.

We've had very troubling problems due to GCC updates.  The source of
this comes from upstream not testing their code with GCC ever since
4.2.1 release.

Long term it may be useful for us to follow upstream.  This would
avoid nasty problems like:

  * Fix panic on early boot.  (Closes: #644417)
    - Switch back to GCC 4.4.
    - Turn optimization down to -O1 (901_disable_optimization_2.diff).

and also allow us to re-enable -O2 and -Werror (both are default in upstream).

OTOH, upstream doesn't yet use clang as default themselves.  Their
transition is stuck because of userland (missing C++ runtime, etc).
I'm also unsure if moving from GCC to Clang may cause performance

Anyway, we can have this discussion after the release.  Even if we
decide to do it, there wouldn't be enough time to test it properly for

Robert Millan

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