Bug#394311: libgl1-mesa-dri: i965_dri.so miscompiled with current gcc

[Ryan Richter]

On Sat, Oct 21, 2006 at 06:52:06PM +0100, Ben Hutchings wrote:
> On Sat, 2006-10-21 at 12:08 -0400, Ryan Richter wrote:
> > On Sat, Oct 21, 2006 at 10:18:41AM +0200, Michel Dänzer wrote:
> > > On Fri, 2006-10-20 at 12:47 -0400, ryan at tau.solarneutrino.net wrote:
> > > > Package: libgl1-mesa-dri
> > > > Version: 6.5.1-0.2
> > > > Severity: normal
> > > > 
> > > > The current build contains a faulty i965_dri.so causing all GL clients
> > > > to crash and lock up the display.  This is apparently caused by a
> > > > miscompilation with gcc-4.1.  Rebuilding with gcc-3.4 fixes the problem.
> > > 
> > > Ben, do you happen to know whether this was built with
> > > -fno-strict-aliasing? If not, that might be worth a try, as the Mesa
> > > code generally isn't strict aliasing safe.
> > 
> > I can't find -fno-strict-aliasing anywhere in configs/debian*, so I
> > don't think anything is built with that.
> 
> I didn't modify any of the build options, so I suppose I can't have used
> -fno-strict-aliasing.  Unfortunately pbuilder doesn't log (or I have not
> configured it to, if that's possible).
> 
> You had better try that because I don't have any machine with an i965 to
> test on.

Yep, adding -fno-strict-aliasing makes it work with gcc-4.1.

patch

diff -Naur mesa-6.5.1/configs/debian mesa-6.5.1-fnsa/configs/debian
--- mesa-6.5.1/configs/debian	2006-10-23 13:44:20.000000000 -0400
+++ mesa-6.5.1-fnsa/configs/debian	2006-10-23 13:45:14.583335930 -0400
@@ -7,9 +7,9 @@
 
 DEBIAN_COMMON_CPPFLAGS = -D_POSIX_SOURCE -D_POSIX_C_SOURCE=199309L -D_SVID_SOURCE -D_BSD_SOURCE -D_GNU_SOURCE -DUSE_XSHM -DPTHREADS `pkg-config --cflags x11 xext`
 
-DEBIAN_COMMON_CFLAGS = -std=c99 -pedantic -Wall -fPIC
+DEBIAN_COMMON_CFLAGS = -std=c99 -pedantic -Wall -fPIC -fno-strict-aliasing
 
-DEBIAN_COMMON_CXXFLAGS = -ansi -pedantic -Wall -fPIC
+DEBIAN_COMMON_CXXFLAGS = -ansi -pedantic -Wall -fPIC -fno-strict-aliasing
 
 DEBIAN_OPT_CFLAGS = -O2
 
diff -Naur mesa-6.5.1/configs/debian-static mesa-6.5.1-fnsa/configs/debian-static
--- mesa-6.5.1/configs/debian-static	2006-10-23 13:44:20.000000000 -0400
+++ mesa-6.5.1-fnsa/configs/debian-static	2006-10-23 13:45:19.624665242 -0400
@@ -7,9 +7,9 @@
 
 DEBIAN_COMMON_CPPFLAGS = -D_POSIX_SOURCE -D_POSIX_C_SOURCE=199309L -D_SVID_SOURCE -D_BSD_SOURCE -DUSE_XSHM -DPTHREADS -I/usr/X11R6/include
 
-DEBIAN_COMMON_CFLAGS = -std=c99 -pedantic -Wall
+DEBIAN_COMMON_CFLAGS = -std=c99 -pedantic -Wall -fno-strict-aliasing
 
-DEBIAN_COMMON_CXXFLAGS = -ansi -pedantic -Wall
+DEBIAN_COMMON_CXXFLAGS = -ansi -pedantic -Wall -fno-strict-aliasing
 
 DEBIAN_OPT_CFLAGS = -O2
 



-ryan