An Objective-C message was sent to a deallocated 'NSThread' object (zombie) at address:

Question

I follow this answer to trace my app for EXC_BAD_ACCESS. Yes, I got a zombie object. When I'm trying to figure out which line of my code is wrong, I found that all of the Responsible Libraries are Foundation.

When I'm trying to do this:

When you double click on any retain/release, instruments will show you line of code where this was performed.

It always takes me to some code with assembly language.

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I don't know how to trace my bug like this...

Update according to the answer of Elike.

The bug did happened when I update the title of a button. I use a timer to update a button title per second. You can tap the button to start/stop it. And I use dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(_auto_duration * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{}); to auto run the method for 300 times (the bug happens randomly during 300 times).

I call the Timer like this _startcounttimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(StartCountTimerMethod) userInfo:nil repeats:YES];

- (void)StartCountTimerMethod
{
    _startcountbtnsec++;
    NSString *secstring = [NSString stringWithFormat:@"%d", _startcountbtnsec];
    [_startbtn setTitle:secstring forState:UIControlStateNormal];
}

And tap on the button will call this method:

- (void)StartBtnClick:(UIButton *)btn
{
    switch (btn.tag) {
        case 0:
            btn.tag = 1;
            [_startbtn setTitle:@"0" forState:UIControlStateNormal];
            _startcountbtnsec = 0;
            [self StartCountTimerStart];
            NSLog(@"Start!");
            break;

        case 1:
            btn.tag = 0;
            [_startbtn setTitle:@"Start" forState:UIControlStateNormal];
            [self StartCountTimerStop];
            NSLog(@"Stop!");
            break;

        default:
            break;  
    }
}

I can't see any problem with updating button text... And the zombie object is "NSThread".Is there any chance that the bug is about button and thread?

Answer 1

I find it sometimes easier to just enable zombies in the schemes's diagnostics: Break on EXC_BAD_ACCESS in XCode?

Looking at your first screenshot the zombie is pretty obvious, but I agree the actual output is too generic. I don't know what your app is about but I would look for something where you update a button text (based on a notification ?).