Bad idea

gistfile1.m

MyCrazyBlock block = ^(BOOL *stop) {
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
        
        // do some work
        
        dispatch_async(dispatch_get_main_queue(), ^{
            *stop = YES;
        });
    });
};



// in your object

if (block) block(&self.shouldStop);

just a wild guess, but what if you call the block with a weak pointer to self?

__weak typeof(self) weakSelf = self;
if (block) block(&weakSelf.shouldStop);

Please ignore the fact that setting the stop BOOL asynchronously never worked anyway ;)

@hiDominik: should not make any difference, as ARC only manages object retain counts. we're dealing with a pointer into an objects memory space here. Nothing that could be retained.