Re: NSAutoreleasePool issue related to Clang and libobjc2

[Quentin Mathé]

Le 2 nov. 2012 à 12:11, Tom Davie a écrit :

> Heya,
> 
> We unfortunately are running into this same issue now.  Did you manage to 
> find a solution to the crash?

Not yet. I was hoping that Richard or David had some ideas about this issue.

Did you try to disable the pool caching code entirely? I should probably try 
that next week.

Cheers,
Quentin.

> On 31 Oct 2012, at 18:37, Quentin Mathé <address@hidden> wrote:
> 
>> Hi,
>> 
>> The NSAutoreleasePool implementation bound to the ARC_RUNTIME has some 
>> issues I think.
>> 
>> For the same current pool instance, it calls push_pool_to_cache() twice, 
>> once in -emptyPool and another -dealloc. Which means a pool still in use can 
>> be reused, then it's possible to get stuck in an infinite loop. For example, 
>> in
>> 
>> - (void) emptyPool
>> {
>> struct autorelease_thread_vars *tv = ARP_THREAD_VARS;
>> 
>> // Infinite loop when pool == pool->_child
>> while (_child)
>>  {
>>    NSAutoreleasePool *pool = _child;
>>    _child = pool->_child;
>>    push_pool_to_cache(tv, pool);
>>  }
>> 
>> Here is a partial backtrace for this problem :
>> 
>> #0  0xb7a29933 in -[NSAutoreleasePool emptyPool] (self=0x8cf7f34, 
>> _cmd=0xb7f3d000)
>>  at NSAutoreleasePool.m:413
>> #1  0xb7a29d07 in -[NSAutoreleasePool dealloc] (self=0x8cf7f34, 
>> _cmd=0xb7f3cfe0)
>>  at NSAutoreleasePool.m:739
>> #2  0xb7a29c6e in -[NSAutoreleasePool release] (self=0x8cf7f34, 
>> _cmd=0xb7f6dc28)
>>  at NSAutoreleasePool.m:732
>> #3  0xb7c29493 in -[NSRunLoop limitDateForMode:] (self=0x85a1b9c, 
>> _cmd=0xb7f6db10, 
>>  mode=0x80f02e4) at NSRunLoop.m:1080
>> #4  0xb7c2bac7 in -[NSRunLoop runMode:beforeDate:] (self=0x85a1b9c, 
>> _cmd=0xb7f8ab78, 
>>  mode=0x80f02e4, date=0x8ea2dbc) at NSRunLoop.m:1255
>> #5  0xb7d4b3db in -[GSMessageHandle sendMessage:beforeDate:] 
>> (self=0x8cf7dcc, 
>>  _cmd=0xb7f8ab10, components=0x86dd12c, when=0x8ea2dbc) at 
>> NSMessagePort.m:1028
>> #6  0xb7d5292c in -[NSMessagePort 
>> sendBeforeDate:msgid:components:from:reserved:] (
>>  self=0x8cf3f34, _cmd=0xb7f46428, when=0x8ea2dbc, msgId=0, 
>> components=0x86dd12c, 
>>  receivingPort=0x8cf5174, length=16) at NSMessagePort.m:1960
>> #7  0xb7a9201d in -[NSConnection(Private) _sendOutRmc:type:] 
>> (self=0x8cf577c, 
>>  _cmd=0xb7f46198, c=0x86dd0bc, msgid=0) at NSConnection.m:3426
>> #8  0xb7a8312b in -[NSConnection(GNUstepExtensions) 
>> forwardInvocation:forProxy:] (
>>  self=0x8cf577c, _cmd=0xb7f4c0f8, inv=0x86dd064, object=0x8cf920c)
>>  at NSConnection.m:2041
>> #9  0xb7ae4ed1 in -[NSDistantObject forwardInvocation:] (self=0x8cf920c, 
>>  _cmd=0xb7f8bba0, anInvocation=0x86dd064) at NSDistantObject.m:606
>> #10 0xb7d5a030 in GSFFIInvocationCallback (cif=0x86dcf50, retp=0xbfffe380, 
>>  args=0xbfffe300, user=0x8eb94b4) at GSFFIInvocation.m:623
>> #11 0xb72e3176 in ?? () from /usr/lib/i386-linux-gnu/libffi.so.6
>> #12 0xb72e3416 in ?? () from /usr/lib/i386-linux-gnu/libffi.so.6
>> #13 0xb7aea7ea in -[NSDistributedNotificationCenter 
>> addObserver:selector:name:object:suspensionBehavior:] (self=0x8cf11d4, 
>> _cmd=0xb7f4d1e8, anObserver=0x8f99244, 
>>  aSelector=0xb5a108e8, notificationName=0xb5a107b8, anObject=0x0, 
>>  suspensionBehavior=2) at NSDistributedNotificationCenter.m:344
>> #14 0xb7aea162 in -[NSDistributedNotificationCenter 
>> addObserver:selector:name:object:] (
>>  self=0x8cf11d4, _cmd=0xb5a10a68, anObserver=0x8f99244, 
>> aSelector=0xb5a108e8, 
>>  notificationName=0xb5a107b8, anObject=0x0) at 
>> NSDistributedNotificationCenter.m:267
>> 
>> If I apply the patch in attachment, it isn't enough to solve the problem, 
>> because I now get a crash I cannot explain when running the NSRunLoop. Here 
>> is the backtrace :
>> 
>> Program received signal SIGSEGV, Segmentation fault.
>> 0xb7852346 in objc_test_class_flag (aClass=0x74696c71, 
>> flag=objc_class_flag_hidden_class)
>>  at ./class.h:248
>> 248          return (aClass->info & (unsigned long)flag) == (unsigned 
>> long)flag;
>> (gdb) bt
>> #0  0xb7852346 in objc_test_class_flag (aClass=0x74696c71, 
>>  flag=objc_class_flag_hidden_class) at ./class.h:248
>> #1  0xb7852d4b in object_getClass (obj=0x8e9454c) at runtime.c:757
>> #2  0xb7d5a799 in GSObjCIsInstance (obj=0x8e9454c) at GSObjCRuntime.m:84
>> #3  0xb7ab3139 in otherTime (other=0x8e9454c) at NSDate.m:109
>> #4  0xb7ab65c4 in -[NSGDate earlierDate:] (self=0x8624f04, _cmd=0xb7f6da60, 
>>  otherDate=0x8e9454c) at NSDate.m:1461
>> #5  0xb7c2bf6a in -[NSRunLoop runMode:beforeDate:] (self=0x85a1b9c, 
>> _cmd=0xb7f6da40, 
>>  mode=0xb7f6d7f0, date=0x8e9454c) at NSRunLoop.m:1269
>> #6  0xb7c2c40b in -[NSRunLoop runUntilDate:] (self=0x85a1b9c, 
>> _cmd=0xb7fd7d58, 
>>  date=0x8e9454c) at NSRunLoop.m:1305
>> #7  0xb7fc5189 in -[UKRunner runTest:onObject:class:] (self=0x8117c4c, 
>> _cmd=0xb7fd7d78, 
>>  testSelector=0x8452e70, testObject=0x8e8177c, testClass=0xb5a38fe0) at 
>> UKRunner.m:344
>> #8  0xb7fc57fe in -[UKRunner runTests:onObject:] (self=0x8117c4c, 
>> _cmd=0xb7fd7e30, 
>>  testMethods=0x8e81724, testObject=0x8e81744) at UKRunner.m:470
>> #9  0xb7fc60e3 in -[UKRunner runTestsInClass:] (self=0x8117c4c, 
>> _cmd=0xb7fd7eb0, 
>>  testClass=0xb5a38fe0) at UKRunner.m:522
>> #10 0xb7fc689e in -[UKRunner runTests:inBundle:principalClass:] 
>> (self=0x8117c4c, 
>>  _cmd=0xb7fd7cf0, testClasses=0x846e79c, bundle=0x8130984, 
>> principalClass=0x0)
>>  at UKRunner.m:560
>> #11 0xb7fc2ecb in -[UKRunner runTests:inBundleAtPath:currentDirectory:] 
>> (self=0x8117c4c, 
>>  _cmd=0xb7fd7e38, testClasses=0x846e79c, bundlePath=0x812c22c, cwd=0x8117c0c)
>>  at UKRunner.m:145
>> #12 0xb7fc3d33 in +[UKRunner runTests] (self=0xb7fd7c40, _cmd=0x804b7c0)
>>  at UKRunner.m:190
>> #13 0x08048977 in main (argc=1, argv=0xbffff814) at main.m:33
>> 
>> Any suggestions would be welcome, I'm a bit stuck :)
>> 
>> I'm using both GNUstep Base and libobjc2 SVN trunk from today, Clang 3.1 
>> (with the non-fragile ABI) and Ubuntu Linux x86-32.
>> 
>> Cheers,
>> Quentin.
>> 
>> <NSAutoreleasePool.m.patch>_______________________________________________
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