iOS app crash only when not debugging

Question

I am using testflight to test my app, and I have a crash that only occurs when the app is built for ad-hoc and distributed through test flight. The relevant crash report details are:

Date/Time:       2012-06-11 09:00:34.638 +0800
OS Version:      iPhone OS 5.1.1 (9B206)
Report Version:  104

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x00000009
Crashed Thread:  0

Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   libobjc.A.dylib                 0x34e74f78 objc_msgSend + 16
1   appName                         0x0002963e __24-[XYPieChart reloadData]_block_invoke_0168 (XYPieChart.m:321)
2   libdispatch.dylib               0x30295c52 _dispatch_call_block_and_release + 6
3   libdispatch.dylib               0x302a0e8a _dispatch_main_queue_callback_4CF$VARIANT$up + 190
4   CoreFoundation                  0x371482a6 __CFRunLoopRun + 1262
5   CoreFoundation                  0x370cb49e CFRunLoopRunSpecific + 294
6   CoreFoundation                  0x370cb366 CFRunLoopRunInMode + 98
7   GraphicsServices                0x3388a432 GSEventRunModal + 130
8   UIKit                           0x30e77cce UIApplicationMain + 1074
9   appName                         0x00003b20 main (main.m:14)
10  appName                         0x00003ad8 0x1000 + 10968

and the code that is referenced - (XYPieChart.m:321)

    [CATransaction begin];
    [CATransaction setAnimationDuration:_animationSpeed];

    [_pieView setUserInteractionEnabled:NO];

    __block NSMutableArray *layersToRemove = nil;
    [CATransaction setCompletionBlock:^{

        if (layersToRemove) {
            [layersToRemove enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
                if (obj)
                    [obj removeFromSuperlayer];
            }];

            [layersToRemove removeAllObjects];
        }

        for(SliceLayer *layer in _pieView.layer.sublayers)
        {
            [layer setZPosition:kDefaultSliceZOrder];
        }

        [_pieView setUserInteractionEnabled:YES];
    }];

    BOOL isOnStart = ([slicelayers count] == 0 && sliceCount);
    NSInteger diff = sliceCount - [slicelayers count];
    layersToRemove = [NSMutableArray arrayWithArray:slicelayers];

    BOOL isOnEnd = ([slicelayers count] && (sliceCount == 0 || sum <= 0));
    if(isOnEnd)
    {
        for(SliceLayer *layer in _pieView.layer.sublayers){
            [self updateLabelForLayer:layer value:0];
            [layer createArcAnimationForKey:@"startAngle"
                                  fromValue:[NSNumber numberWithDouble:_startPieAngle]
                                    toValue:[NSNumber numberWithDouble:_startPieAngle] 
                                   Delegate:self];
            [layer createArcAnimationForKey:@"endAngle" 
                                  fromValue:[NSNumber numberWithDouble:_startPieAngle]
                                    toValue:[NSNumber numberWithDouble:_startPieAngle] 
                                   Delegate:self];
        }
        [CATransaction commit];
        return;
    }

I would be able to track down the problem if I could reproduce it when debugging but it only seems to occur when built for ad-hoc. Thanks!

Edit: Using the simulator, I have tracked down the problem to a EXC_BAD_ACCESS at this line

[layersToRemove enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

Answer 1

I ended up working out the problem. In my compiler settings, somehow, ARC wasn't enabled for Ad-Hoc builds resulting in weird behaviour. Before I worked this out, allocating the __block variable worked because in non-ARC environments, __block variables are not retained automatically.

Changed compiler settings so that all builds use ARC and everything was fixed.