Dispatch Behavior

main.m

int main(int argc, const char * argv[])
{

    @autoreleasepool {
	    
		dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

		dispatch_block_t block = ^{
			int a = 5;
			NSLog(@"%p = %d", &a, a);
		};
		
		block();
		
		dispatch_async(queue, block);
		
		dispatch_async(queue, ^{
			block();
		});
		
		dispatch_async(queue, ^{
			dispatch_sync(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
				block();
			});
		});
		
		sleep(10);
	}
    return 0;
}

/*
OUTPUT:
2013-04-23 15:47:37.546 BlockTest[29703:303] 0x7fff5fbff86c = 5
2013-04-23 15:47:37.548 BlockTest[29703:1a03] 0x100780e5c = 5
2013-04-23 15:47:37.548 BlockTest[29703:1803] 0x100580e7c = 5
2013-04-23 15:47:37.548 BlockTest[29703:1b03] 0x1022a5dcc = 5
*/