[Qt-interest] BLEND_SOURCE_OVER_ARGB32_SSE2 (used to) crash [SOLVED in Qt 4.7.1] - example app: Screenie

[Zeljko]

Oliver.Knoll at comit.ch wrote:

> On 2010-11-20 Zeljko Zeljko wrote:
> 
>>> ...
>>> And indeed, "Screenie" works as expected again with Qt 4.7.1 - in case
>>> someone else stumbles across the same issue ;)
>> 
>> No it's not fixed yet (haven't tried distro packaged 4.7.1, but from
>> fedora koji packages 4.7.0-8 which merged some patches from 4.7.1 it
>> still crashes).
> 
> So how can you say "it is not fixed yet [in 4.7.1]" if you tried a
> distro-Qt which "merged some patches from 4.7.1"? "Some" != "All" ;)
> 
>> I've opened this issue at kde bug tracker as I can
>> reproduce it only with oxygen theme and kde 4.5.XX with qt-4.7. However,
>> kde-4.5.3 with qt-4.6.3 works fine.Default qt styles works as expected
>> (plastique,motif,gtk ...etc). Running app with -graphicssystem raster
>> doesn't crash. Here is gdb stacktrace
>> https://bugs.kde.org/show_bug.cgi?id=254889
> 
> Are we talking about the same app "Screenie"

No, I'm not talking about Screenie at all, but about
BLEND_SOURCE_OVER_ARGB32_SSE2 which is NOT guilty for weird crashes  (yes
there was bug with raster but fixed 4.7.1 and screenie was affected because
of that bug).Seem that gcc (>= 4.4) is reason why some apps have weird
crashes no matter of code quality, and it worked ok in qt < 4.7.0 just
because sse2 wasn't enabled on most distros (or not enabled at all).
-mstackrealign fixes problem for such apps.
Look here:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40838

I know that this problem does not have anything with screenie, but some ppl
will run into such problems (like me), so they can find answer here :)

zeljko