Re: [CFT]: ClangBSD is selfhosting, we need testers now

Roman Divacky schrieb am 2010-04-21:
> On Wed, Apr 21, 2010 at 05:20:57PM +0200, Alexander Best wrote:
> > i might have stumbled upon a problem with clang. i've compiled a
> > kernel from
> > the clang branch using `make kernel INSTKERNNAME=clang` and booted
> > from it.
> > i'm now experiencing audio problems with mp3s and certain video
> > files.
> > playback is awfully slow and the audio output gets distorted
> > massively. `top`
> > however reports no high cpu load and `vmstat -i` doesn't report
> > anything
> > unusual either.

> > this problem doesn't occur with a regular gcc-kernel.

> > both kernels are running under a regular (gcc) world.

> > i thought it might be a problem with acpi, but disabling acpi
> > (hint.acpi.0.disabled=1) gives me a system freeze.

> I've heard about this problem but did not manage to reproduce that.

> can you try to bisect what file is being miscompiled? ie. compile
> half of the kernel with gcc and half with clang and bisect this
> way to a single file.

> we can work from there...

i've identified the problem to be somewhere in sys/dev/sound. i've removed
"device sound" and "device hda_snd" from my kernel config and
rebuild/reinstalled both kernels (gcc and clang). i then booted the clang
kernel and loaded various sound.ko and snd_hda.ko combination. here're the
results:

sound.ko (clang) snd_hda.ko (clang) => BROKEN
sound.ko (clang) snd_hda.ko (gcc)   => BROKEN
sound.ko (gcc) snd_hda.ko (gcc)     => OK
sound.ko (gcc) snd_hda.ko (clang)   => OK

i've attached a log documenting all clang warnings that get issued when
building sys/modules/sound.

in addition to those warnings i get a lot of these, but i guess they aren't
harmful:

clang: warning: argument unused during compilation: '-funroll-loops'
clang: warning: argument unused during compilation: '-finline-limit=8000'
clang: warning: argument unused during compilation: '--param
inline-unit-growth=100'
clang: warning: argument unused during compilation: '--param
large-function-growth=1000'
clang: warning: argument unused during compilation: '-mfpmath=387'
clang: warning: argument unused during compilation: '-fformat-extensions'
clang: warning: argument unused during compilation: '-funroll-loops'
clang: warning: argument unused during compilation: '-finline-limit=8000'
clang: warning: argument unused during compilation: '--param
inline-unit-growth=100'
clang: warning: argument unused during compilation: '--param
large-function-growth=1000'
clang: warning: argument unused during compilation: '-mfpmath=387'

-- 
Alexander Best