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The following call to getaddrinfo makes Python segfault:
$ python
Python 2.7.2 (default, Jun 20 2012, 16:23:33) 
[GCC 4.2.1 Compatible Apple Clang 4.0 (tags/Apple/clang-418.0.60)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import socket
>>> socket.getaddrinfo("localhost", None, 0, 0, 0, socket.AI_NUMERICSERV)
Segmentation fault: 11
The combination of no port (None) and socket.AI_NUMERICSERV makes no sense (I used it by mistake) but we probably don't want to segfault anyway.

Linux manual page: "If AI_NUMERICSERV is specified in hints.ai_flags and service is not NULL, then service must point to a string containing a numeric port number."
So it looks like None is accepted on Linux. I checked: the example doesn't crash.

The crash occurs in OS X's libsystem_info on 10.8.
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 libsystem_info.dylib 	0x00007fff86bacd9e mdns_addrinfo + 299
1 libsystem_info.dylib 	0x00007fff86badae2 search_addrinfo + 152
2 libsystem_info.dylib 	0x00007fff86b97f6d si_addrinfo + 1641
3 libsystem_info.dylib 	0x00007fff86b9785c getaddrinfo + 171
4 _socket.so 	0x0000000100516524 socket_getaddrinfo + 500
It's also reproducible back on OS X 10.6 crashing there in libSystem. (It looks like earlier versions of OS X don't support the AI_NUMERICSERV flag.) So it would appear to be a long-standing OS X bug. Possible actions: open an Apple incident and patch socket.getaddrinfo to catch this case.

Looks like a bug in libSystem, see mdns_addrinfo in <http://www.opensource.apple.com/source/Libinfo/Libinfo-406.17/lookup.subproj/mdns_module.c>. Its handling of AI_NUMERICSERV doesn't match that of si_getaddrinfo.c at the same location.
I'll file a bug with Apple, anyone running into this problem migh want to do so as well (Apple's tracker is more or less a popularity contest, the more an issue is report, the more likely it is to get fixed).
I'm in favor of working around this bug on OSX by settings the servname to "0" when AI_NUMERICSERVICE is set and the passed in service name is None. I\m working on a patch.

That's interesting... this also crashes:
>>> socket.getaddrinfo("localhost", "0", 0, 0, 0, socket.AI_NUMERICSERV)
While using another port number does not.
The attached patches for the default branch fixes the issue for me (on OSX 10.8). 
The same approach should also work with 2.7 (but the patch likely won't apply cleanly due to the use of TABs for indents in 2.7 and spaces in 3.x).
Open issue: should there be a testcase for this problem?

I've filed radar #13271126 for this in Apple's tracker.

On win7, the original example and '0' version give
[(23, 0, 0, '', ('::1', 0, 0, 0)), (2, 0, 0, '', ('127.0.0.1', 0))]
I think a testcase would be good.

My bug submission at Apple was closed as a duplicate of radar 13058317.
Given the state of testing of getaddrinfo a testcase will be easier than expected, just pasting the call in this bugreport into the right testcase will match the style of most other checks in that testcase.

I've updated the patch: it now contains a testcase (although the getaddrinfo tests are stretching the definition of the word, the new test only checks that the function doesn't crash)

New changeset f4981d8eb401 by Ronald Oussoren in branch '2.7':
Issue #17269: Workaround for a platform bug in getaddrinfo on OSX
http://hg.python.org/cpython/rev/f4981d8eb401
New changeset 3c4a5dc29417 by Ronald Oussoren in branch '3.3':
Issue #17269: Workaround for a platform bug in getaddrinfo on OSX
http://hg.python.org/cpython/rev/3c4a5dc29417
New changeset 24ffb0148729 by Ronald Oussoren in branch 'default':
(3.3->default) Issue #17269: Workaround for a platform bug in getaddrinfo on OSX
http://hg.python.org/cpython/rev/24ffb0148729 

Hi, I think this broke the tiger buildbot:
http://buildbot.python.org/all/builders/x86%20Tiger%203.x/builds/6368/steps/test/logs/stdio 

That sucks. A patch should be easy, but I probably won't get around to that until sunday.

I've tested a patch for the 2.7 branch on a 10.5 machine (which also failed to build without the patch), and will commit once I've finished running the testsuite on the 3.3 branch as well.

New changeset 4d1e4bc6c5b5 by Ronald Oussoren in branch '2.7':
Ensure that the fix for #17269 also works on OSX 10.4
http://hg.python.org/cpython/rev/4d1e4bc6c5b5
New changeset ef103e7e7af2 by Ronald Oussoren in branch '3.3':
Ensure that the fix for #17269 also works on OSX 10.4
http://hg.python.org/cpython/rev/ef103e7e7af2
New changeset 062f1985a5b7 by Ronald Oussoren in branch 'default':
(3.3->default) Ensure that the fix for #17269 also works on OSX 10.4
http://hg.python.org/cpython/rev/062f1985a5b7 

The buildbot seems to be happy right now (at least as far as getaddrinfo is concerned).