Open Radar

 
Exceptions thrown in gcd-queued main queue blocks do not result in the 'except' of a try-except handler to be called.

 When wrapping a runloop spin in a try except block, one might expect any exceptions thrown in any code called as a result of the spin to be caught be a try except handler around the spin. This is not the case for blocks added to the run loop using dispatch_async(dispatch_get_main_queue(), block)

In other words, the program crashes and "Caught" is not printed in the below.

    dispatch_async(dispatch_get_main_queue(), ^{
        [[NSException exceptionWithName:@"ExceptionException" reason:@"Exception" userInfo:nil] raise];
    });
    
    @try {
        
        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
    } @catch (NSException *e) {
        NSLog(@"Caught");
    }

Steps to Reproduce:

Run the attached project

Expected Results:

No crash. "Caught" is printed to the console. 

Actual Results:

Crash

Regression:

Notes:

Exceptions thrown as a result of code in a queued performSelector:withObject:afterDelay:  are caught gracefully. A commented line is provided to demonstrate this.

14-Feb-2013 09:29 PM Nate Griswold:
'ExceptionNotCaught.zip' was successfully uploaded