[Python-Dev] HEADS UP: Compilation risk with new GCC 4.5.0 (original) (raw)
Jesus Cea jcea at jcea.es
Wed May 12 15:13:21 CEST 2010
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[Zlib-devel] HEADS UP: Apparent bad compilation under (just released) GCC 4.5.0 <http://mail.madler.net/pipermail/zlib-devel_madler.net/2010-May/002267.html>
GCC Bugzilla Bug 40838 gcc shouldn't assume that the stack is aligned http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40838
Short history: new GCC 4.5.0 (released a month ago), when compiling with
- -O3, is adding MMX/SSE instructions that requires stack aligned to 16 byte. This is wrong, since x86 ABI only requires stack aligned to 4 bytes.
If you compile EVERYTHING with GCC 4.5.0, you are safe (I guess!), but if your environment has mixed compiled code (for instance, the OS libraries), you can possibly "core dump". If you have an old compiled Python and you update libs compiled with GCC 4.5.0, you can crash in the process.
Psyco is showing the issue, but it is not the culprit. It only leaves
- -correctly- the stack in not 16-byte alignment. But there are plenty of examples of crashes not related to python+psyco.
Proposal: add "-fno-tree-vectorize" to compilation options for 2.7/3.2. Warm 2.3/2.4/2.5/2.6/3.0/3.1 users. Or warm users compiling with GCC 4.5.0.
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