Python3 has a configure switch --with-computed-gotos that uses the gcc computed goto extension as an optimization.  When we attempt to enable that in rawhide, it causes an internal compiler error.  Cloning the relevant portions of the python RFE here:

--- Additional comment from a.badger on 2010-08-06 17:20:51 EDT ---

Setting to rawhide again -- we'll apply this for the F15 cycle starting now and see how it goes.  I've verified that the patch from http://bugs.python.org/issue6603

has been applied in the tarball we're using.  I didn't take benchmarks but we can do that anytime during the F15 cycle by running benchmarks, turning off computed-goto, rerunning benchmarks.

There's a %global at the top of the spec to toggle this on and off in the build.  Just change:

%global with_computed_gotos yes
==>
%global with_computed_gotos no

I've kicked off a build with computed-gotos yes.  I' need to compare test suite output to the last build without computed-gotos when it completes.

https://koji.fedoraproject.org/koji/buildinfo?buildID=181256
http://koji.fedoraproject.org/koji/taskinfo?taskID=2386306

--- Additional comment from dmalcolm on 2010-08-06 17:35:56 EDT ---

Builds failed with internal compiler errors:

on x86_64:
http://koji.fedoraproject.org/koji/getfile?taskID=2386310&name=build.log
gcc -pthread -c -fno-strict-aliasing -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -D_GNU_SOURCE -fPIC -fwrapv    -I. -IInclude -I/builddir/build/BUILD/Python-3.1.2/Include -I/usr/lib64/libffi-3.0.9/include   -fPIC -DPy_BUILD_CORE -o Python/ceval.o /builddir/build/BUILD/Python-3.1.2/Python/ceval.c
  [snip parallel tasks]
/builddir/build/BUILD/Python-3.1.2/Python/ceval.c: In function 'PyEval_EvalFrameEx':
/builddir/build/BUILD/Python-3.1.2/Python/ceval.c:3004:1: internal compiler error: in save_call_clobbered_regs, at caller-save.c:911
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://bugzilla.redhat.com/bugzilla> for instructions.
Preprocessed source stored into /tmp/ccQpsjeF.out file, please attach this to your bugreport.
make: *** [Python/ceval.o] Error 1


on i386:
http://koji.fedoraproject.org/koji/getfile?taskID=2386311&name=build.log
gcc -pthread -c -fno-strict-aliasing -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i686 -mtune=atom -fasynchronous-unwind-tables -D_GNU_SOURCE -fPIC -fwrapv    -I. -IInclude -I/builddir/build/BUILD/Python-3.1.2/Include -I/usr/lib/libffi-3.0.9/include   -fPIC -DPy_BUILD_CORE -o Python/ceval.o /builddir/build/BUILD/Python-3.1.2/Python/ceval.c
  [snip parallel tasks]
/builddir/build/BUILD/Python-3.1.2/Python/ceval.c: In function 'PyEval_EvalFrameEx':
/builddir/build/BUILD/Python-3.1.2/Python/ceval.c:3004:1: internal compiler error: in save_call_clobbered_regs, at caller-save.c:911

--- Additional comment from a.badger on 2010-08-06 18:22:45 EDT ---

Created an attachment (id=437273)
preprocessed output from gcc

Here's the output taken from the buildroot