Re: NSAutoreleasePool issue related to Clang and libobjc2

[Tom Davie]

Heya,

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

Thanks

Tom Davie

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.
> 
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