I am using NSOperation and NSOperationQueue for performing a sequence of operations, all dependent on each other (2 on 1, 3 on 2, etc...). I set the dependency after I create the operations. I am encountering problems when the queue completes: the program crashes in the _release part of the code, apparently when the NSOperations are getting released. Note that they all get released at the end by the queue, because it is only after the very last one which depends on the second last one, which depends on etc... that they can be released. If I remove any dependency, the code runs fine. If I change waitUntilFinished: to NO, it crashes, if it is YES, it does not.
I have isolated the problem to the following code which does not use any of my custom classes. NSOperation by default is a class that does absolutely nothing. Yet, this still crashes when all operations have completed. Therefore, it appears I am not using NSOperationQueue properly but can't see what is wrong. I am running on 10.9 and I have noticed that in general Maverick 10.9 is much more sensitive to these issues than 10.8.
I call this method from the main Thread with a Menu item:
- (void) testOperations:(id)object
{
NSOperationQueue* queue = [ [ NSOperationQueue alloc ] init ];
NSMutableArray* array = [ NSMutableArray array ];
for ( int i = 0; i < 10000; i++)
[ array addObject: [[[ NSOperation alloc ] init ] autorelease ] ];
for ( int i = 1; i < [ array count ]; i++)
[[ array objectAtIndex:i ] addDependency:[array objectAtIndex:i-1]]; // remove this and no crash
[ queue addOperations: array waitUntilFinished:NO ]; // Change to YES, no crash
[ queue autorelease ]; // or release, it does not make a difference, in fact leaking the memory makes no difference: the code crashes when the queue is removing the NSOperations
}
This will crash every single time with:
bool objc::DenseMapBase , objc_object*, unsigned long, objc::DenseMapInfo, true: (EXC_BAD_ACCESS)
The full stack is:
#0 0x9104d81b in objc::DenseMapBase<objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*> >, objc_object*, unsigned long, objc::DenseMapInfo<objc_object*>, true>::find(objc_object* const&) ()
#1 0x910384e3 in _objc_rootReleaseWasZero ()
#2 0x9104d5d9 in -[NSObject release] ()
#3 0x99e41224 in CFRelease ()
#4 0x99e56277 in -[__NSArrayM dealloc] ()
#5 0x9104d5ef in -[NSObject release] ()
#6 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#7 0x9104d5ef in -[NSObject release] ()
#8 0x97f62ac8 in -[NSOperation dealloc] ()
#9 0x9104d5ef in -[NSObject release] ()
#10 0x99e41224 in CFRelease ()
#11 0x99e56277 in -[__NSArrayM dealloc] ()
#12 0x9104d5ef in -[NSObject release] ()
#13 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#14 0x9104d5ef in -[NSObject release] ()
#15 0x97f62ac8 in -[NSOperation dealloc] ()
#16 0x9104d5ef in -[NSObject release] ()
#17 0x99e41224 in CFRelease ()
#18 0x99e56277 in -[__NSArrayM dealloc] ()
#19 0x9104d5ef in -[NSObject release] ()
#20 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#21 0x9104d5ef in -[NSObject release] ()
#22 0x97f62ac8 in -[NSOperation dealloc] ()
#23 0x9104d5ef in -[NSObject release] ()
#24 0x99e41224 in CFRelease ()
#25 0x99e56277 in -[__NSArrayM dealloc] ()
#26 0x9104d5ef in -[NSObject release] ()
#27 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#28 0x9104d5ef in -[NSObject release] ()
#29 0x97f62ac8 in -[NSOperation dealloc] ()
#30 0x9104d5ef in -[NSObject release] ()
#31 0x99e41224 in CFRelease ()
#32 0x99e56277 in -[__NSArrayM dealloc] ()
#33 0x9104d5ef in -[NSObject release] ()
#34 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#35 0x9104d5ef in -[NSObject release] ()
#36 0x97f62ac8 in -[NSOperation dealloc] ()
#37 0x9104d5ef in -[NSObject release] ()
#38 0x99e41224 in CFRelease ()
#39 0x99e56277 in -[__NSArrayM dealloc] ()
#40 0x9104d5ef in -[NSObject release] ()
#41 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#42 0x9104d5ef in -[NSObject release] ()
#43 0x97f62ac8 in -[NSOperation dealloc] ()
#44 0x9104d5ef in -[NSObject release] ()
#45 0x99e41224 in CFRelease ()
#46 0x99e56277 in -[__NSArrayM dealloc] ()
#47 0x9104d5ef in -[NSObject release] ()
#48 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#49 0x9104d5ef in -[NSObject release] ()
#50 0x97f62ac8 in -[NSOperation dealloc] ()
#10722 0x9104d5ef in -[NSObject release] ()
#10723 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10724 0x9104d5ef in -[NSObject release] ()
#10725 0x97f62ac8 in -[NSOperation dealloc] ()
#10726 0x9104d5ef in -[NSObject release] ()
#10727 0x99e41224 in CFRelease ()
#10728 0x99e56277 in -[__NSArrayM dealloc] ()
#10729 0x9104d5ef in -[NSObject release] ()
#10730 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10731 0x9104d5ef in -[NSObject release] ()
#10732 0x97f62ac8 in -[NSOperation dealloc] ()
#10733 0x9104d5ef in -[NSObject release] ()
#10734 0x99e41224 in CFRelease ()
#10735 0x99e56277 in -[__NSArrayM dealloc] ()
#10736 0x9104d5ef in -[NSObject release] ()
#10737 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10738 0x9104d5ef in -[NSObject release] ()
#10739 0x97f62ac8 in -[NSOperation dealloc] ()
#10740 0x9104d5ef in -[NSObject release] ()
#10741 0x99e41224 in CFRelease ()
#10742 0x99e56277 in -[__NSArrayM dealloc] ()
#10743 0x9104d5ef in -[NSObject release] ()
#10744 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10745 0x9104d5ef in -[NSObject release] ()
#10746 0x97f62ac8 in -[NSOperation dealloc] ()
#10747 0x9104d5ef in -[NSObject release] ()
#10748 0x99e41224 in CFRelease ()
#10749 0x99e56277 in -[__NSArrayM dealloc] ()
#10750 0x9104d5ef in -[NSObject release] ()
#10751 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10752 0x9104d5ef in -[NSObject release] ()
#10753 0x97f62ac8 in -[NSOperation dealloc] ()
#10754 0x9104d5ef in -[NSObject release] ()
#10755 0x99e41224 in CFRelease ()
#10756 0x99e56277 in -[__NSArrayM dealloc] ()
#10757 0x9104d5ef in -[NSObject release] ()
#10758 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10759 0x9104d5ef in -[NSObject release] ()
#10760 0x97f62ac8 in -[NSOperation dealloc] ()
#10761 0x9104d5ef in -[NSObject release] ()
#10762 0x99e41224 in CFRelease ()
#10763 0x99e56277 in -[__NSArrayM dealloc] ()
#10764 0x9104d5ef in -[NSObject release] ()
#10765 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10766 0x9104d5ef in -[NSObject release] ()
#10767 0x97f62ac8 in -[NSOperation dealloc] ()
#10768 0x9104d5ef in -[NSObject release] ()
#10769 0x99e41224 in CFRelease ()
#10770 0x99e56277 in -[__NSArrayM dealloc] ()
#10771 0x9104d5ef in -[NSObject release] ()
#10772 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10773 0x9104d5ef in -[NSObject release] ()
#10774 0x97f62ac8 in -[NSOperation dealloc] ()
#10775 0x9104d5ef in -[NSObject release] ()
#10776 0x99e41224 in CFRelease ()
#10777 0x99e56277 in -[__NSArrayM dealloc] ()
#10778 0x9104d5ef in -[NSObject release] ()
#10779 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10780 0x9104d5ef in -[NSObject release] ()
#10781 0x97f62ac8 in -[NSOperation dealloc] ()
#10782 0x9104d5ef in -[NSObject release] ()
#10783 0x99e41224 in CFRelease ()
#10784 0x99e56277 in -[__NSArrayM dealloc] ()
#10785 0x9104d5ef in -[NSObject release] ()
#10786 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10787 0x9104d5ef in -[NSObject release] ()
#10788 0x97f62ac8 in -[NSOperation dealloc] ()
#10789 0x9104d5ef in -[NSObject release] ()
#10790 0x99e41224 in CFRelease ()
#10791 0x99e56277 in -[__NSArrayM dealloc] ()
#10792 0x9104d5ef in -[NSObject release] ()
#10793 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10794 0x9104d5ef in -[NSObject release] ()
#10795 0x97f62ac8 in -[NSOperation dealloc] ()
#10796 0x9104d5ef in -[NSObject release] ()
#10797 0x99e41224 in CFRelease ()
#10798 0x99e56277 in -[__NSArrayM dealloc] ()
#10799 0x9104d5ef in -[NSObject release] ()
#10800 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10801 0x9104d5ef in -[NSObject release] ()
#10802 0x97f62ac8 in -[NSOperation dealloc] ()
#10803 0x9104d5ef in -[NSObject release] ()
#10804 0x99e41224 in CFRelease ()
#10805 0x99e56277 in -[__NSArrayM dealloc] ()
#10806 0x9104d5ef in -[NSObject release] ()
#10807 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10808 0x9104d5ef in -[NSObject release] ()
#10809 0x97f62ac8 in -[NSOperation dealloc] ()
#10810 0x9104d5ef in -[NSObject release] ()
#10811 0x99e41224 in CFRelease ()
#10812 0x99e56277 in -[__NSArrayM dealloc] ()
#10813 0x9104d5ef in -[NSObject release] ()
#10814 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10815 0x9104d5ef in -[NSObject release] ()
#10816 0x97f62ac8 in -[NSOperation dealloc] ()
#10817 0x9104d5ef in -[NSObject release] ()
#10818 0x99e41224 in CFRelease ()
#10819 0x99e56277 in -[__NSArrayM dealloc] ()
#10820 0x9104d5ef in -[NSObject release] ()
#10821 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10822 0x9104d5ef in -[NSObject release] ()
#10823 0x97f62ac8 in -[NSOperation dealloc] ()
#10824 0x9104d5ef in -[NSObject release] ()
#10825 0x99e41224 in CFRelease ()
#10826 0x99e56277 in -[__NSArrayM dealloc] ()
#10827 0x9104d5ef in -[NSObject release] ()
#10828 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10829 0x9104d5ef in -[NSObject release] ()
#10830 0x97f62ac8 in -[NSOperation dealloc] ()
#10831 0x9104d5ef in -[NSObject release] ()
#10832 0x99e41224 in CFRelease ()
#10833 0x99e56277 in -[__NSArrayM dealloc] ()
#10834 0x9104d5ef in -[NSObject release] ()
#10835 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10836 0x9104d5ef in -[NSObject release] ()
#10837 0x97f62ac8 in -[NSOperation dealloc] ()
#10838 0x9104d5ef in -[NSObject release] ()
#10839 0x99e41224 in CFRelease ()
#10840 0x99e56277 in -[__NSArrayM dealloc] ()
#10841 0x9104d5ef in -[NSObject release] ()
#10842 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10843 0x9104d5ef in -[NSObject release] ()
#10844 0x97f62ac8 in -[NSOperation dealloc] ()
#10845 0x9104d5ef in -[NSObject release] ()
#10846 0x99e41224 in CFRelease ()
#10847 0x99e56277 in -[__NSArrayM dealloc] ()
#10848 0x9104d5ef in -[NSObject release] ()
#10849 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10850 0x9104d5ef in -[NSObject release] ()
#10851 0x97f62ac8 in -[NSOperation dealloc] ()
#10852 0x9104d5ef in -[NSObject release] ()
#10853 0x99e41224 in CFRelease ()
#10854 0x99e56277 in -[__NSArrayM dealloc] ()
#10855 0x9104d5ef in -[NSObject release] ()
#10856 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10857 0x9104d5ef in -[NSObject release] ()
#10858 0x97f62ac8 in -[NSOperation dealloc] ()
#10859 0x9104d5ef in -[NSObject release] ()
#10860 0x99e41224 in CFRelease ()
#10861 0x99e56277 in -[__NSArrayM dealloc] ()
#10862 0x9104d5ef in -[NSObject release] ()
#10863 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10864 0x9104d5ef in -[NSObject release] ()
#10865 0x97f62ac8 in -[NSOperation dealloc] ()
#10866 0x9104d5ef in -[NSObject release] ()
#10867 0x99e41224 in CFRelease ()
#10868 0x99e56277 in -[__NSArrayM dealloc] ()
#10869 0x9104d5ef in -[NSObject release] ()
#10870 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10871 0x9104d5ef in -[NSObject release] ()
#10872 0x97f62ac8 in -[NSOperation dealloc] ()
#10873 0x9104d5ef in -[NSObject release] ()
#10874 0x99e41224 in CFRelease ()
#10875 0x99e56277 in -[__NSArrayM dealloc] ()
#10876 0x9104d5ef in -[NSObject release] ()
#10877 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10878 0x9104d5ef in -[NSObject release] ()
#10879 0x97f62ac8 in -[NSOperation dealloc] ()
#10880 0x9104d5ef in -[NSObject release] ()
#10881 0x99e41224 in CFRelease ()
#10882 0x99e56277 in -[__NSArrayM dealloc] ()
#10883 0x9104d5ef in -[NSObject release] ()
#10884 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10885 0x9104d5ef in -[NSObject release] ()
#10886 0x97f62ac8 in -[NSOperation dealloc] ()
#10887 0x9104d5ef in -[NSObject release] ()
#10888 0x99e41224 in CFRelease ()
#10889 0x99e56277 in -[__NSArrayM dealloc] ()
#10890 0x9104d5ef in -[NSObject release] ()
#10891 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10892 0x9104d5ef in -[NSObject release] ()
#10893 0x97f62ac8 in -[NSOperation dealloc] ()
#10894 0x9104d5ef in -[NSObject release] ()
#10895 0x99e41224 in CFRelease ()
#10896 0x99e56277 in -[__NSArrayM dealloc] ()
#10897 0x9104d5ef in -[NSObject release] ()
#10898 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10899 0x9104d5ef in -[NSObject release] ()
#10900 0x97f62ac8 in -[NSOperation dealloc] ()
#10901 0x9104d5ef in -[NSObject release] ()
#10902 0x99e41224 in CFRelease ()
#10903 0x99e56277 in -[__NSArrayM dealloc] ()
#10904 0x9104d5ef in -[NSObject release] ()
#10905 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10906 0x9104d5ef in -[NSObject release] ()
#10907 0x97f62ac8 in -[NSOperation dealloc] ()
#10908 0x9104d5ef in -[NSObject release] ()
#10909 0x99e41224 in CFRelease ()
#10910 0x99e56277 in -[__NSArrayM dealloc] ()
#10911 0x9104d5ef in -[NSObject release] ()
#10912 0x97f62b22 in -[__NSOperationInternal dealloc] ()
#10913 0x9104d5ef in -[NSObject release] ()
#10914 0x97f62ac8 in -[NSOperation dealloc] ()
#10915 0x9104d5ef in -[NSObject release] ()
#10916 0x97f49cca in __NSOQSchedule_f ()
#10917 0x9c1c9e21 in _dispatch_async_redirect_invoke ()
#10918 0x9c1c53a6 in _dispatch_client_callout ()
#10919 0x9c1c7467 in _dispatch_root_queue_drain ()
#10920 0x9c1c8732 in _dispatch_worker_thread2 ()
#10921 0x960c2dab in _pthread_wqthread ()
The full crash context is (bold for crash line):
libobjc.A.dylib`objc::DenseMapBase<objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*> >, objc_object*, unsigned long, objc::DenseMapInfo<objc_object*>, true>::find(objc_object* const&):
0x9104d800: pushl %ebp
0x9104d801: movl %esp, %ebp
0x9104d803: pushl %esi
0x9104d804: subl $20, %esp
0x9104d807: leal -8(%ebp), %eax
0x9104d80a: movl %eax, 8(%esp)
0x9104d80e: movl 16(%ebp), %eax
0x9104d811: movl %eax, 4(%esp)
0x9104d815: movl 12(%ebp), %esi
0x9104d818: movl %esi, (%esp)
**0x9104d81b: calll 0x9104d9b6 ; bool objc::DenseMapBase<objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*> >, objc_object*, unsigned long, objc::DenseMapInfo<objc_object*>, true>::LookupBucketFor<objc_object*>(objc_object* const&, std::__1::pair<objc_object*, unsigned long> const*&) const**
0x9104d820: movl 12(%esi), %ecx
0x9104d823: shll $3, %ecx
0x9104d826: addl (%esi), %ecx
0x9104d828: movl 8(%ebp), %edx
0x9104d82b: testb %al, %al
0x9104d82d: je 0x9104d836 ; objc::DenseMapBase<objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*> >, objc_object*, unsigned long, objc::DenseMapInfo<objc_object*>, true>::find(objc_object* const&) + 54
0x9104d82f: movl -8(%ebp), %eax
0x9104d832: movl %eax, (%edx)
0x9104d834: jmp 0x9104d838 ; objc::DenseMapBase<objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*> >, objc_object*, unsigned long, objc::DenseMapInfo<objc_object*>, true>::find(objc_object* const&) + 56
0x9104d836: movl %ecx, (%edx)
0x9104d838: movl %ecx, 4(%edx)
0x9104d83b: addl $20, %esp
0x9104d83e: popl %esi
0x9104d83f: popl %ebp
0x9104d840: ret $4
0x9104d843: nop
I tried using a pre-created queue, this makes no difference. Apparently, with dependencies, this code is a problem with XCode 5.0, 32-bit.
Edit: In fact, I can isolate the problem much further. An empty Cocoa Application project in XCOde 5.0 on 10.9 with ARC on and a single method will crash. If it does not on your computer,
increase 4269 to anything bigger:
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
NSOperationQueue* aQueue = [[ NSOperationQueue alloc ] init ];
NSMutableArray* array = [ NSMutableArray array ];
for ( int i = 0; i < 4269; i++)
[ array addObject: [ [NSOperation alloc ] init ]];
for ( int i = 1; i < [ array count ]; i++)
[[ array objectAtIndex:i ] addDependency:[array objectAtIndex:i-1]];
[ aQueue addOperations: array waitUntilFinished:NO ];
}
