I just wanted to share an observation in case Python developers are interested: Python 2.7.1 doesn't build with the current gcc 4.6 svn. Note that gcc 4.6 is now in "bug-fix only" mode. Some details: Fedora 14 64-bit. The first time I noticed the problem was in Nov or early Dec 2010; I'm pretty sure it worked in Oct maybe still early Nov. Python configured simply with ./configure g++ (GCC) 4.6.0 20101206 (experimental) % make /bin/sh: line 1: 41686 Segmentation fault (core dumped) CC='gcc -pthread' LDSHARED='gcc -pthread -shared ' OPT='-DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes' ./python -E ./setup.py build make: *** [sharedmods] Error 139 g++ (GCC) 4.6.0 20110108 (experimental) % make XXX lineno: 743, opcode: 0 Traceback (most recent call last): File "/net/theta/raid1/rwgk/junk/Python-2.7.1/Lib/site.py", line 62, in <module> import os File "/net/theta/raid1/rwgk/junk/Python-2.7.1/Lib/os.py", line 743, in <module> def urandom(n): SystemError: unknown opcode make: *** [sharedmods] Error 1 make finishes OK if I configure --with-pydebug. Therefore my guess is that there is an optimizer bug in the current gcc 4.6 that's only triggered by a specific construct in Python. (A lot of other stuff builds and runs fine.) BTW: I've been doing gcc pre-release testing regularly for many year, starting with gcc 3.3. This is the first time I see the Python build fail persistently for several weeks.