On a Snow Leopard system, doing this core dumps:

import multiprocessing
lck1=multiprocessing.Lock()

with lck1:
    print "foo"

The stack trace:

Process:         Python [23100]
Path:           
/System/Library/Frameworks/Python.framework/Versions/2.6/Resources/Python.app/Contents/MacOS/Python
Identifier:      Python
Version:         ??? (???)
Code Type:       X86-64 (Native)
Parent Process:  zsh [23055]

Date/Time:       2009-09-18 10:39:39.611 +0530
OS Version:      Mac OS X 10.6.1 (10B504)
Report Version:  6

Interval Since Last Report:          83665 sec
Crashes Since Last Report:           60
Per-App Crashes Since Last Report:   55
Anonymous UUID:                      38A426BB-52F7-4282-9FA8-A04AB8896489

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x00000043000000ee
Crashed Thread:  0  Dispatch queue: com.apple.main-thread

Thread 0 Crashed:  Dispatch queue: com.apple.main-thread
0   org.python.python             	0x0000000100096763
_PyArg_ParseTupleAndKeywords_SizeT + 113
1   _multiprocessing.so           	0x00000001001fa8c8 sem_timedwait_save
+ 456
2   org.python.python             	0x00000001000891df PyEval_EvalFrameEx
+ 15001
3   org.python.python             	0x000000010008accf PyEval_EvalCodeEx
+ 1803
4   org.python.python             	0x000000010008ad62 PyEval_EvalCode + 54
5   org.python.python             	0x00000001000a265a Py_CompileString + 78
6   org.python.python             	0x00000001000a44dd
PyRun_InteractiveOneFlags + 503
7   org.python.python             	0x00000001000a4615
PyRun_InteractiveLoopFlags + 206
8   org.python.python             	0x00000001000a4685
PyRun_AnyFileExFlags + 76
9   org.python.python             	0x00000001000b0286 Py_Main + 2718
10  org.python.python.app         	0x0000000100000e6c start + 52

Thread 0 crashed with X86 Thread State (64-bit):
  rax: 0x0000004300000043  rbx: 0x0000000100200150  rcx:
0x00000001001fc7f0  rdx: 0x00000001001fb632
  rdi: 0x00000001001af050  rsi: 0x000000010003af24  rbp:
0x00007fff5fbfeff0  rsp: 0x00007fff5fbfef20
   r8: 0x0000000100096748   r9: 0x00007fff5fbff030  r10:
0x0000000000000000  r11: 0x00000001001fa86f
  r12: 0x00000000ffffffff  r13: 0x00000001004a4570  r14:
0x0000000100123100  r15: 0x00000001001af050
  rip: 0x0000000100096763  rfl: 0x0000000000010206  cr2: 0x00000043000000ee

Binary Images:
       0x100000000 -        0x100000ff7  org.python.python.app 2.6 (2.6)
<BDEA119D-4E2F-D97F-07BA-713A6E5A39B6>
/System/Library/Frameworks/Python.framework/Versions/2.6/Resources/Python.app/Contents/MacOS/Python
       0x100004000 -        0x100114ff7  org.python.python 2.6.1 (2.6.1)
<01EBD0D4-F181-045F-C7A8-B7B3C5D4204F>
/System/Library/Frameworks/Python.framework/Versions/2.6/Python
       0x1001f0000 -        0x1001f2ff7  readline.so ??? (???)
<A8236667-A9DD-30A5-6DE8-201C6EF317E6>
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload/readline.so
       0x1001f8000 -        0x1001fbfff  _multiprocessing.so ??? (???)
<03672D74-6FAC-DE76-6DE6-604A8C0F2D50>
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload/_multiprocessing.so
       0x1004b0000 -        0x1004ccff7  libedit.2.dylib ??? (???)
<F9D005F8-74B8-CC05-2697-24C49E0CC1EF> /usr/lib/libedit.2.dylib
       0x1004db000 -        0x1004e0fff  itertools.so ??? (???)
<06555874-952C-C770-64BF-6BC7A2455E10>
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload/itertools.so
       0x1004e8000 -        0x1004f4fff  cPickle.so ??? (???)
<98485D07-D504-74EB-B3A1-4EBB2474BFE6>
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload/cPickle.so
       0x1004fa000 -        0x1004fbfff  cStringIO.so ??? (???)
<7600C3A8-3C81-2A81-0853-B09107768C8C>
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload/cStringIO.so
       0x100540000 -        0x100541ff7  _functools.so ??? (???)
<1CE29F88-7B8C-77CC-5E87-555BA210EA8F>
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload/_functools.so
       0x100545000 -        0x100546ff7  time.so ??? (???)
<5F01F2A9-8557-5DF1-F006-44E02E0469CE>
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload/time.so
       0x10054d000 -        0x100550fff  _collections.so ??? (???)
<1F62A5C3-6E6C-D0BC-7AA6-DA2820B5F157>
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload/_collections.so
       0x100556000 -        0x100559fff  operator.so ??? (???)
<68C1CC88-5F73-E029-5C19-685BBADACFA6>
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload/operator.so
       0x10055f000 -        0x10055ffff  _weakref.so ??? (???)
<89F1302D-1CFA-7B9B-4425-70DA55215DAE>
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload/_weakref.so
       0x1005a3000 -        0x1005a7ff7  _struct.so ??? (???)
<33156F5C-52ED-7167-533F-15D6CF031150>
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload/_struct.so
       0x1005ad000 -        0x1005affe7  binascii.so ??? (???)
<5CFE3DC5-850B-B79D-8310-0BA97540841A>
/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload/binascii.so
    0x7fff5fc00000 -     0x7fff5fc3bdef  dyld 132.1 (???)
<B633F790-4DDB-53CD-7ACF-2A3682BCEA9F> /usr/lib/dyld
    0x7fff80bc1000 -     0x7fff80bc5ff7  libmathCommon.A.dylib ??? (???)
<95718673-FEEE-B6ED-B127-BCDBDB60D4E5> /usr/lib/system/libmathCommon.A.dylib
    0x7fff829f4000 -     0x7fff82bb2ff7  libSystem.B.dylib ??? (???)
<66102D4E-6C8B-77D0-6766-2A1788B20C6F> /usr/lib/libSystem.B.dylib
    0x7fff85ebc000 -     0x7fff85efbfef  libncurses.5.4.dylib ??? (???)
<E0A07C12-D912-DF26-9E38-C50484D96EB0> /usr/lib/libncurses.5.4.dylib
    0x7fff85f81000 -     0x7fff85f92fef  libz.1.dylib ??? (???)
<3A7A4C48-A4C8-A78A-8B87-C0DDF6601AC8> /usr/lib/libz.1.dylib
    0x7fffffe00000 -     0x7fffffe01fff  libSystem.B.dylib ??? (???)
<66102D4E-6C8B-77D0-6766-2A1788B20C6F> /usr/lib/libSystem.B.dylib

Model: MacBookPro2,2, BootROM MBP22.00A5.B07, 2 processors, Intel Core 2
Duo, 2.16 GHz, 2 GB, SMC 1.12f5
Graphics: ATI Radeon X1600, ATY,RadeonX1600, PCIe, 128 MB
Memory Module: global_name
AirPort: spairport_wireless_card_type_airport_extreme (0x168C, 0x87),
Atheros 5416: 2.0.19.4
Bluetooth: Version 2.2.1f7, 2 service, 1 devices, 1 incoming serial ports
Network Service: AirPort, AirPort, en1
Serial ATA Device: Hitachi HTS541612J9SA00, 111.79 GB
Parallel ATA Device: HL-DT-ST DVDRW GWA4080MA
USB Device: Built-in iSight, 0x05ac  (Apple Inc.), 0x8501, 0xfd400000
USB Device: IR Receiver, 0x05ac  (Apple Inc.), 0x8240, 0x5d200000
USB Device: Apple Internal Keyboard / Trackpad, 0x05ac  (Apple Inc.),
0x021a, 0x1d200000
USB Device: Bluetooth USB Host Controller, 0x05ac  (Apple Inc.), 0x8205,
0x7d100000

Additional Info: Snow Leopard is shipping with Python 2.6.1 64 bit build.

Reproducible here. Fails with Apple 2.6.1 in 64-bit mode but *not* in 
32-bit mode.  Also does not fail on 10.6 with recent 64-bit 4-way trunk  
built on 10.5.

$ arch -i386 /usr/bin/python2.6
Python 2.6.1 (r261:67515, Jul  7 2009, 23:51:51) 
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import multiprocessing
>>> lck1=multiprocessing.Lock()
>>> with lck1:
...   print "foo"
... 
foo
>>> ^D
$ arch -x86_64 /usr/bin/python2.6
Python 2.6.1 (r261:67515, Jul  7 2009, 23:51:51) 
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import multiprocessing
>>> lck1=multiprocessing.Lock()
>>> with lck1:
...   print "foo"
... 
Segmentation fault

Jesse: is this something you can look into? 

This is a crash of multiprocessing on MacOSX 10.6 with a 64-bit build of 
python.

Don't know what exact release OS X ships with, but it
looks like you're being bitten by this:

http://bugs.python.org/issue5261

AFAIK: Tim is correct. Unfortunately, this has already been fixed - as 
much as it kills me, there's not much I can do to fix this for Snow 
Leopard.

Jesse: Apple can fix their own copy of python (which is 2.6.1), I was more 
worried about the upcoming 2.6.3 release.

I'll file a bug with Apple and poke their Python maintainer once 2.6.3  is 
released.

Ronald, could you email me the incantation for a full-on 64 bit build, 
I'll double check this on 26-maint. I just forget the magic build flags 
all the time.

Ronald, if you can also put the magic incantations on a wiki page
somewhere it'd really help me out. I can then download 2.6.2 and build
it for snow leopard. 

I can put up a downloadable version for other people if needed.

I'm assuming this will bite a lot of people on snow leopard.

To build universal build of Python use "--enable-universalsdk" or "--
enable-universalsdk=/" (the former defaults to the 10.4 SDK, which 
doesn't support a 64-bit build).  You can then use the "--with-
universal-archs" option to select the type of build you want.

Anyway, I can confirm that this does not affect either the trunk or the 
HEAD of release26-maint.

Closing this issue as out of date.


aaditya: you don't have to provide a seperate build for 10.6. Python 
2.6.3 will be released soon and we will ship a Mac installer for that.

As an aside: never replace /System/Library/Framework/Python.framework by 
something else. Apple ships a patched version of Python and replacing 
the system version might break the system or 3th-party applications.