libffi on 32bit is broken on linux

[fijall]

BPO	17423
Nosy	@gpshead, @vstinner, @alex, @asvetlov, @skrah
Superseder	bpo-17245: ctypes libffi needs to align the x86 stack to 16 bytes
Files	x.py x.c ffi.diff

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2013-03-18.20:58:36.806>
created_at = <Date 2013-03-14.21:09:03.242>
labels = ['type-crash']
title = 'libffi on 32bit is broken on linux'
updated_at = <Date 2013-03-18.20:59:11.903>
user = 'https://bugs.python.org/fijall'

bugs.python.org fields:

activity = <Date 2013-03-18.20:59:11.903>
actor = 'gregory.p.smith'
assignee = 'none'
closed = True
closed_date = <Date 2013-03-18.20:58:36.806>
closer = 'gregory.p.smith'
components = []
creation = <Date 2013-03-14.21:09:03.242>
creator = 'fijall'
dependencies = []
files = ['29410', '29411', '29412']
hgrepos = []
issue_num = 17423
keywords = ['patch']
message_count = 7.0
messages = ['184193', '184201', '184313', '184316', '184318', '184323', '184520']
nosy_count = 7.0
nosy_names = ['gregory.p.smith', 'vstinner', 'hodgestar', 'alex', 'asvetlov', 'skrah', 'fijall']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = None
status = 'closed'
superseder = '17245'
type = 'crash'
url = 'https://bugs.python.org/issue17423'
versions = []

[fijall]

The bug is a little tricky to reproduce. You need a 32bit linux. First compile x.c with:

gcc -O3 -g -shared -o x.so x.c -std=c99 -msse3 -ftree-vectorize -mfpmath=sse

and run x.py. It segfaults because the alignment of stack is not preserved (and it's assumed on a modern linux). Patch attached.

[skrah]

Is this the same as bpo-17245?

[vstinner]

libffi is not part of Python project, but Python has a copy for system which don't provide system libffi. You should report the issue upstream:
http://sourceware.org/libffi/

(Or is the issue already fixed upstream?)

[fijall]

The issue is reported upstrem and is/will be fixed

[fijall]

It's not "a copy for systems that don't provide libffi", since CPython makes zero effort to try to use system libffi if present.

[alex]

The patch has been merged into libffi upstream: https://github.com/atgreen/libffi/pull/32

[gpshead]

I'm taking care of this with a libffi update per bpo-17192 and bpo-19245. Thanks for the upstream fix into libffi 3.0.13 alex. :)