Re: Odd Crash when adding table columns manually
Re: Odd Crash when adding table columns manually
- Subject: Re: Odd Crash when adding table columns manually
- From: Eric Gorr <email@hidden>
- Date: Wed, 19 Jan 2011 14:55:56 -0500
If anyone is interested, this odd crash turns out to be the same issue I was struggling with in the 'Window Controllers & Window Deallocation' ( http://bit.ly/gzd1LI ) thread.
If in the dealloc method of the table controller, I set the table's dataSource and delegate to nil, it will no longer crash. Instruments no longer reports any zombies. Upon a normal quit, Instruments does not report any leaks either.
Again, the documentation on Weak References can be found at:
Memory Management Programming Guide - Weak References
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/MemoryMgmt/Articles/mmObjectOwnership.html#//apple_ref/doc/uid/20000043-1044135-BCICCFAE
Mike Ash has an interesting article on this topic as well:
Zeroing Weak References in Objective-C
http://www.mikeash.com/pyblog/friday-qa-2010-07-16-zeroing-weak-references-in-objective-c.html
On Jan 12, 2011, at 10:08 AM, Eric Gorr wrote:
> Try grabbing the project again - I have cleaned up a few things which should make this a bit easier.
>
> http://ericgorr.net/cocoadev/TableColumnTest.zip
>
> It should crash everytime as long as in TableController.m the column are not being removed from the table first. You will have to go in an comment out that line of code yourself.
>
> I have also uploaded two screen recordings showing the crash.
>
> http://ericgorr.net/cocoadev/TableColumnTestCrash01.m4v
> http://ericgorr.net/cocoadev/TableColumnTestCrash02.m4v
>
> The first movie is just using xcode & the debugger.
> The second movie is running with zombies.
>
>>>> Am 11.01.2011 um 18:06 schrieb Eric Gorr:
>>>>
>>>>> I've got a sample test project at:
>>>>>
>>>>> http://ericgorr.net/cocoadev/TableColumnTest.zip
>>>>>
>>>>> which reproduces the strange crash.
>>>>>
>>>>> I have a NSTableView to which I need to add NSTableColumns manually using the addTableColumn: method. The problem is that for some reason when I release the window and everything is being deallocated, someone has an extra retain on the table column and it sticks around. This causes a crash because the OS tries to redraw the table which really isn't there.
>>>>>
>>>>> Note: With the code as written, it will only cause a crash sometimes...if you comment back in the call to the EventAvail function in WindowTestAppDelegate.m, it will crash every time...this is how I ended up finding the odd behavior to begin with - I am working with a cocoa/carbon app and EventAvail is still being called.
>>>>>
>>>>> I can avoid the crash if, in my TableController class, I manually remove the table column from the table first. Is this what I am expected to do if I manually add the column? I would not have thought so, but perhaps I am wrong...?
>>>>>
>>>>> In TableController.m, I have the function GetNewColumn which creates a new table column. After I alloc and init the column, I can log the retain count of the column and see that it is 1. After I call setWidth: on the table column, I can see that the retain count is 2.
>>>>>
>>>>> Can anyone shed some light on what might be going on here and why it is crashing?
>>>>>
>>>>> (if it matters, I am still running on 10.6.5)
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