I'm not optimistic that this will be reproducible elsewhere.   I get a silent failure with 2.6 and a crash dialog with 2.7 with the following script.   All elements are necessary, although the "pkg_resources" import may be arbitrary, and reproduces if it comes from the latest setuptools or if it comes from Distribute.    I've attached the crash report generated by OSX in the event that someone knows how to interpret it.   The script fails for me every time, though not for other people I've had test.


import pkg_resources

import urllib
import multiprocessing

def sub():
    print "about to call getproxies !"
    urllib.getproxies()
    print "getproxies has completed !"
    
process = multiprocessing.Process(target=sub)
process.start()

print "hi!"

process.join()



Process:         Python [79964]
Path:            /Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python
Identifier:      Python
Version:         ??? (???)
Code Type:       X86 (Native)
Parent Process:  Python [79963]

Date/Time:       2010-07-28 17:24:19.281 -0400
OS Version:      Mac OS X 10.6.4 (10F569)
Report Version:  6

Interval Since Last Report:          1137309 sec
Crashes Since Last Report:           87
Per-App Crashes Since Last Report:   86
Anonymous UUID:                      848E03B6-EF61-45EA-9BB7-BF9E584CC670

Exception Type:  EXC_BAD_ACCESS (SIGBUS)
Exception Codes: KERN_PROTECTION_FAILURE at 0x0000000000000104
Crashed Thread:  0  Dispatch queue: CFMachPort

Thread 0 Crashed:  Dispatch queue: CFMachPort
0   libSystem.B.dylib             	0x94419bdd _dispatch_wakeup + 91
1   libSystem.B.dylib             	0x9454a1f2 _dispatch_queue_push_list_slow + 37
2   libSystem.B.dylib             	0x94419c22 _dispatch_wakeup + 160
3   libSystem.B.dylib             	0x944196e6 _dispatch_source_create2 + 194
4   libSystem.B.dylib             	0x94419278 dispatch_source_timer_create_f + 286
5   libSystem.B.dylib             	0x94419158 dispatch_source_timer_create + 81
6   com.apple.CoreFoundation      	0x92fde72a ___CFMachPortCreateWithPort2_block_invoke_1 + 762
7   libSystem.B.dylib             	0x944190c3 dispatch_barrier_sync_f + 78
8   libSystem.B.dylib             	0x94418f9d dispatch_sync + 48
9   com.apple.CoreFoundation      	0x92fde350 _CFMachPortCreateWithPort2 + 272
10  com.apple.CoreFoundation      	0x92fe5e1c CFMachPortCreate + 204
11  com.apple.CoreFoundation      	0x92fe5c39 _CFXNotificationCenterCreate + 281
12  com.apple.CoreFoundation      	0x92fe5ad6 _CFXNotificationGetHostCenter + 86
13  com.apple.CoreFoundation      	0x92feb432 __CFXPreferencesGetSourceForTriplet + 354
14  com.apple.CoreFoundation      	0x92fea6ad __CFXPreferencesGetSearchListForBundleID + 205
15  com.apple.CoreFoundation      	0x92fea555 CFPreferencesCopyAppValue + 53
16  com.apple.SystemConfiguration 	0x90fc7348 SCDynamicStoreCopyProxies + 44
17  _scproxy.so                   	0x00746e31 get_proxies + 33
18  org.python.python             	0x000ca2b3 PyEval_EvalFrameEx + 20419
19  org.python.python             	0x000cbc88 PyEval_EvalFrameEx + 27032
20  org.python.python             	0x000cbc88 PyEval_EvalFrameEx + 27032
21  org.python.python             	0x000cc4ba PyEval_EvalCodeEx + 2042
22  org.python.python             	0x00041ca2 function_call + 162
23  org.python.python             	0x0000f375 PyObject_Call + 85
24  org.python.python             	0x000c7d5b PyEval_EvalFrameEx + 10859
25  org.python.python             	0x000cbc88 PyEval_EvalFrameEx + 27032
26  org.python.python             	0x000cbc88 PyEval_EvalFrameEx + 27032
27  org.python.python             	0x000cc4ba PyEval_EvalCodeEx + 2042
28  org.python.python             	0x00041ca2 function_call + 162
29  org.python.python             	0x0000f375 PyObject_Call + 85
30  org.python.python             	0x00021c66 instancemethod_call + 422
31  org.python.python             	0x0000f375 PyObject_Call + 85
32  org.python.python             	0x0007c8a7 slot_tp_init + 87
33  org.python.python             	0x0007b2d0 type_call + 176
34  org.python.python             	0x0000f375 PyObject_Call + 85
35  org.python.python             	0x000c8ad6 PyEval_EvalFrameEx + 14310
36  org.python.python             	0x000cbc88 PyEval_EvalFrameEx + 27032
37  org.python.python             	0x000cc4ba PyEval_EvalCodeEx + 2042
38  org.python.python             	0x000cc647 PyEval_EvalCode + 87
39  org.python.python             	0x000f0ae8 PyRun_FileExFlags + 168
40  org.python.python             	0x000f1a23 PyRun_SimpleFileExFlags + 867
41  org.python.python             	0x0010a42b Py_Main + 3163
42  org.python.python             	0x00001f82 0x1000 + 3970
43  org.python.python             	0x00001ea9 0x1000 + 3753

Thread 0 crashed with X86 Thread State (32-bit):
  eax: 0xa04c511c  ebx: 0xa04c50f4  ecx: 0x00000001  edx: 0x00000100
  edi: 0x003011e0  esi: 0x003011d0  ebp: 0xbfffd5e8  esp: 0xbfffd5c0
   ss: 0x0000001f  efl: 0x00010206  eip: 0x94419bdd   cs: 0x00000017
   ds: 0x0000001f   es: 0x0000001f   fs: 0x00000000   gs: 0x00000037
  cr2: 0x00000104

Binary Images:
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0x939ae000 - 0x93a56ffb  com.apple.QD 3.35 (???) <37854644-864D-A3F2-7116-89F2F28E1CA4> /System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/QD.framework/Versions/A/QD
0x93b06000 - 0x93b6affb  com.apple.htmlrendering 72 (1.1.4) <4D451A35-FAB6-1288-71F6-F24A4B6E2371> /System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/HTMLRendering.framework/Versions/A/HTMLRendering
0x93be7000 - 0x93c97ff3  com.apple.ColorSync 4.6.3 (4.6.3) <AA1076EA-7665-3005-A837-B661260DBE54> /System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/ColorSync.framework/Versions/A/ColorSync
0x93cbf000 - 0x93ccdfe7  libz.1.dylib 1.2.3 (compatibility 1.0.0) <3CE8AA79-F077-F1B0-A039-9103A4A02E92> /usr/lib/libz.1.dylib
0x93d1f000 - 0x93d9ffeb  com.apple.SearchKit 1.3.0 (1.3.0) <2F5DE102-A203-7905-7D12-FCBCF17BAEF8> /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/SearchKit.framework/Versions/A/SearchKit
0x94287000 - 0x942a3fe3  com.apple.openscripting 1.3.1 (???) <480D41B6-F98E-8E21-CA3C-4CA6A9752D3D> /System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/OpenScripting.framework/Versions/A/OpenScripting
0x943ea000 - 0x943ebff7  com.apple.audio.units.AudioUnit 1.6.3 (1.6.3) <F3872A43-6157-098D-F9DD-210187B95FD3> /System/Library/Frameworks/AudioUnit.framework/Versions/A/AudioUnit
0x943ec000 - 0x943f3ff3  com.apple.print.framework.Print 6.1 (237.1) <9758733E-7FBB-29CF-04F3-0D6D6B4C6A78> /System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/Print.framework/Versions/A/Print
0x943f4000 - 0x9459afeb  libSystem.B.dylib 125.2.0 (compatibility 1.0.0) <3441F338-2218-6D36-3F95-3A16FBF6713D> /usr/lib/libSystem.B.dylib
0x9459b000 - 0x945deff7  com.apple.NavigationServices 3.5.4 (182) <ED268D94-E544-5548-AA59-7EC70DCB5EE4> /System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/NavigationServices.framework/Versions/A/NavigationServices
0x94610000 - 0x94612ff7  libRadiance.dylib ??? (???) <AB06F616-E3EA-5966-029A-8AA44BBE5B28> /System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/ImageIO.framework/Versions/A/Resources/libRadiance.dylib
0x94949000 - 0x94992fe7  libTIFF.dylib ??? (???) <9CFF48CC-4852-4D06-17AC-3C947C824159> /System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/ImageIO.framework/Versions/A/Resources/libTIFF.dylib
0x94a96000 - 0x94cf9fef  com.apple.security 6.1.1 (37594) <8AE73F5F-936C-80F6-B05B-A50C3082569C> /System/Library/Frameworks/Security.framework/Versions/A/Security
0x94cfa000 - 0x94d47feb  com.apple.DirectoryService.PasswordServerFramework 6.0 (6.0) <E2632F3E-6B5C-2E92-CD11-15BC0CE109CA> /System/Library/PrivateFrameworks/PasswordServer.framework/Versions/A/PasswordServer
0x94d48000 - 0x94d68fe7  libresolv.9.dylib 41.0.0 (compatibility 1.0.0) <751955F3-21FB-A03A-4E92-1F3D4EFB8C5B> /usr/lib/libresolv.9.dylib
0x94d69000 - 0x94dacff7  libGLU.dylib ??? (???) <B50572FF-3EAC-FD98-1A01-6B718D98F67F> /System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGLU.dylib
0x95a9b000 - 0x95aa5ffb  com.apple.speech.recognition.framework 3.11.1 (3.11.1) <6E3481DF-645E-6095-0CD7-9BEBEC2ED9D1> /System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/SpeechRecognition.framework/Versions/A/SpeechRecognition
0x95adf000 - 0x95b12ff7  com.apple.AE 496.4 (496.4) <582F5E9D-1B8E-6D03-EBB8-AA85F66253E2> /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/AE.framework/Versions/A/AE
0x95b53000 - 0x95be5fe3  com.apple.print.framework.PrintCore 6.2 (312.5) <2A8801E6-6D9F-68F5-947D-A1D68BE4F876> /System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/PrintCore.framework/Versions/A/PrintCore
0x95be6000 - 0x95be6ff7  com.apple.Carbon 150 (152) <9252D5F2-462D-2C15-80F3-109644D6F704> /System/Library/Frameworks/Carbon.framework/Versions/A/Carbon
0x95c29000 - 0x95d06ff7  com.apple.vImage 4.0 (4.0) <64597E4B-F144-DBB3-F428-0EC3D9A1219E> /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vImage.framework/Versions/A/vImage
0x95d07000 - 0x95d12ff7  libGL.dylib ??? (???) <B87E0676-F5EF-8DA3-6DEE-13C43B3832A7> /System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib
0x95d13000 - 0x95d37ff7  libJPEG.dylib ??? (???) <5CE96981-6B2A-D15B-4A17-E7BD329095B6> /System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/ImageIO.framework/Versions/A/Resources/libJPEG.dylib
0x95e37000 - 0x9619fff7  com.apple.QuartzCore 1.6.2 (227.22) <4288F0D2-0C87-F054-C372-8764B44DE024> /System/Library/Frameworks/QuartzCore.framework/Versions/A/QuartzCore
0x966a7000 - 0x966a8ff7  com.apple.TrustEvaluationAgent 1.1 (1) <07E7D892-5054-23A8-7144-3F19D3BFD48F> /System/Library/PrivateFrameworks/TrustEvaluationAgent.framework/Versions/A/TrustEvaluationAgent
0x966dc000 - 0x966e2fff  com.apple.CommonPanels 1.2.4 (91) <2438AF5D-067B-B9FD-1248-2C9987F360BA> /System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/CommonPanels.framework/Versions/A/CommonPanels
0x96a03000 - 0x96aacff7  com.apple.CFNetwork 454.9.7 (454.9.7) <B740E1BD-01B7-34C2-2A9A-6DBC68B1EA5B> /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/CFNetwork.framework/Versions/A/CFNetwork
0x96aad000 - 0x96b5bff3  com.apple.ink.framework 1.3.3 (107) <0AFEBD7C-D83C-7847-C075-9B427505F7F0> /System/Library/Frameworks/Carbon.framework/Versions/A/Frameworks/Ink.framework/Versions/A/Ink
0x97aae000 - 0x97abaff7  libkxld.dylib ??? (???) <322A4B52-8305-3081-6B74-813C3A87A56D> /usr/lib/system/libkxld.dylib
0x97abb000 - 0x97ac4ff7  com.apple.DiskArbitration 2.3 (2.3) <E9C40767-DA6A-6CCB-8B00-2D5706753000> /System/Library/Frameworks/DiskArbitration.framework/Versions/A/DiskArbitration
0x97ade000 - 0x97b22ff3  com.apple.coreui 2 (114) <E6096C79-94B0-730E-6070-3AE93B5678FE> /System/Library/PrivateFrameworks/CoreUI.framework/Versions/A/CoreUI
0x97b23000 - 0x97e43feb  com.apple.CoreServices.CarbonCore 861.13 (861.13) <52803668-3669-36BD-57DD-078FBA835081> /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/CarbonCore.framework/Versions/A/CarbonCore
0x97e44000 - 0x98279ff7  libLAPACK.dylib 219.0.0 (compatibility 1.0.0) <5E2D2283-57DE-9A49-1DB0-CD027FEFA6C2> /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libLAPACK.dylib
0x9827a000 - 0x983a6fff  com.apple.audio.toolbox.AudioToolbox 1.6.3 (1.6.3) <B9469F98-E349-3C27-86C4-B99AD178FDF1> /System/Library/Frameworks/AudioToolbox.framework/Versions/A/AudioToolbox
0x9852e000 - 0x98620ff7  libcrypto.0.9.8.dylib 0.9.8 (compatibility 0.9.8) <D2C86308-F998-C83D-F49B-CD484D4EFE6A> /usr/lib/libcrypto.0.9.8.dylib
0x98854000 - 0x988a5ff7  com.apple.HIServices 1.8.0 (???) <BE4D9BC1-B527-D416-F4EB-FFB66EDA5DBB> /System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/HIServices.framework/Versions/A/HIServices
0x989e2000 - 0x989efff7  com.apple.NetFS 3.2.1 (3.2.1) <E483137C-8239-E4DE-821C-05A9C22726AB> /System/Library/Frameworks/NetFS.framework/Versions/A/NetFS
0x98a64000 - 0x98be6fe7  libicucore.A.dylib 40.0.0 (compatibility 1.0.0) <2314BD12-0821-75BB-F3BC-98D324CFD30A> /usr/lib/libicucore.A.dylib
0x98be7000 - 0x98c56ff7  libvMisc.dylib 268.0.1 (compatibility 1.0.0) <5C3D7DA5-29EB-A745-E32B-26DBF547D532> /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libvMisc.dylib
0x98c57000 - 0x98cf2ff7  com.apple.ApplicationServices.ATS 4.3 (???) <7ECA252B-5F67-2816-A4F0-73E1DC833728> /System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/ATS.framework/Versions/A/ATS
0x98cf3000 - 0x994e2557  com.apple.CoreGraphics 1.543.50 (???) <74533178-5C90-0F54-1B06-2E1C5251ED5D> /System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/CoreGraphics.framework/Versions/A/CoreGraphics
0x99501000 - 0x99501ff7  com.apple.Accelerate.vecLib 3.6 (vecLib 3.6) <1DEC639C-173D-F808-DE0D-4070CC6F5BC7> /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/vecLib
0x996a9000 - 0x996c4ff7  libPng.dylib ??? (???) <36A3D75E-5178-4358-7F02-444E276D61AD> /System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/ImageIO.framework/Versions/A/Resources/libPng.dylib
0x998cc000 - 0x998f4ff7  libxslt.1.dylib 3.24.0 (compatibility 3.0.0) <769EF4B2-C1AD-73D5-AAAD-1564DAEA77AF> /usr/lib/libxslt.1.dylib
0x998f5000 - 0x99945ff7  com.apple.framework.familycontrols 2.0.1 (2010) <B9762E20-543D-13B9-F6BF-E8585F04CA01> /System/Library/PrivateFrameworks/FamilyControls.framework/Versions/A/FamilyControls
0xffff0000 - 0xffff1fff  libSystem.B.dylib ??? (???) <3441F338-2218-6D36-3F95-3A16FBF6713D> /usr/lib/libSystem.B.dylib

Model: MacBookPro6,2, BootROM MBP61.0057.B09, 2 processors, Intel Core i7, 2.66 GHz, 8 GB, SMC 1.58f16
Graphics: NVIDIA GeForce GT 330M, NVIDIA GeForce GT 330M, PCIe, 512 MB
Graphics: Intel HD Graphics, Intel HD Graphics, Built-In, 288 MB
Memory Module: global_name
AirPort: spairport_wireless_card_type_airport_extreme (0x14E4, 0x93), Broadcom BCM43xx 1.0 (5.10.131.16.1)
Bluetooth: Version 2.3.3f8, 2 service, 12 devices, 1 incoming serial ports
Network Service: AirPort, AirPort, en1
Serial ATA Device: Hitachi HTS545050B9SA02, 465.76 GB
Serial ATA Device: MATSHITADVD-R   UJ-898
USB Device: Hub, 0x0424  (SMSC), 0x2514, 0xfa100000
USB Device: Apple Internal Keyboard / Trackpad, 0x05ac  (Apple Inc.), 0x0236, 0xfa120000
USB Device: BRCM2070 Hub, 0x0a5c  (Broadcom Corp.), 0x4500, 0xfa110000
USB Device: Bluetooth USB Host Controller, 0x05ac  (Apple Inc.), 0x8218, 0xfa113000
USB Device: Internal Memory Card Reader, 0x05ac  (Apple Inc.), 0x8403, 0xfa130000
USB Device: Hub, 0x0424  (SMSC), 0x2514, 0xfd100000
USB Device: Built-in iSight, 0x05ac  (Apple Inc.), 0x8507, 0xfd110000
USB Device: IR Receiver, 0x05ac  (Apple Inc.), 0x8242, 0xfd120000

I get crash dialog with both 2.6 and 2.7 (both installed from macports) under Mac OS X 10.6.4.

There have been similar problems reported in the past when subprocesses cause OS X CoreFoundation interfaces to be first called from the subprocess and not the main process.  A quick workaround is to make a call from the main process.  In this case, adding a call to urllib.getproxies() before calling Process appears to fix the problem for me.

right...so I would propose the function calls in question emit a warning or something when called in a child process.   this would save lots of people many hours of grief.

There should be a way to provide a permanent fix to avoid the problem; that will take more investigation. This was just a workaround suggestion.

mike: the crash is a bug and I will try to find a solution for it. 

A number of Apple APIs have issues with being called in child processes created with fork without calling exec. This sucks big time.

Interestingly enough I don't get the crash in a copy of 2.7, but do get the crash in a copy of 2.6. The former was build on 10.6, the later on 10.5.

Both 3.1 and 3.2 crash reliably for me (after porting the script to py3k)

/usr/bin/python doesn't crash, but that's because it doesn't get proxy information from the system.

<http://developer.apple.com/mac/library/technotes/tn2005/tn2083.html#SECDAEMONVSFRAMEWORKS> explains the issue that Ned mentions, I'm not sure yet if this crash is related to that.

This seems to be a minimal program to reproduce the problem:


import sys
import os
import platform

platform.mac_ver()

if sys.version_info[0] == 2:
    import urllib
else:
    import urllib.request

if os.fork() == 0:
    print ("about to call getproxies !")
    if sys.version_info[0] == 2:
        print (urllib.getproxies())
    else:
        print (urllib.request.getproxies())
    print ("getproxies has completed !")

else:
    os.wait()

The call to platform.mac_ver is essential, without that call the problem goed away.

This explains why my 2.7 build doesn't crash: I've committed a patch at the EuroPython sprints that replaces the platform.mac_ver implementation by one that reads the OSX version from an XML file instead of calling low-level Apple APIs, and those lowlevel APIs somehow cause the breakage (see also issue #7895)

This means that the problem should go away in the next release for all branches.

mike: are you able to test if the problem goes away when you build python from source using a subversion checkout?



Note that this doesn't mean that the underlying problem is gone, you'll probably still run into problems when the main program is a GUI program that using multiprocessing to start work in the background.

Yeah we are fine if I build the release2.7-maint branch.    Also just noticed that this bug prevents really basic things, like using urllib2 from a Pylons application that's running in "daemon" mode.  Pretty major, though unusual that I have some colleagues who don't have the issue with 2.6.

I agree that this is an annoying bug, and I'm glad that it doesn't occur in the 27-maint branch.

I won't close this issue yet though, I'd prefer to add a unittest that demonstrates the problem in 2.7.0 and shows that the problem is fixed afterwords.

Basically something like this:


   pid = os.fork() 
   if pid == 0:
       # child
       import platform
       import urllib
       urllib.get_proxies()
       os._exit(0)

    else:
       # parent
       exit = sys.waitpid(pid, 0)
       self.assertEquals(exit, 0)

Changing the type, since the crash bug has been fixed for a long time.