my_dispatch_async_2.c

static atomic_int executed_count;

void my_dispatch_async(dispatch_queue_t queue, dispatch_block_t block) {
    dispatch_block_t wrapped_block = ^{
        ++executed_count;
        block();
    };
    struct Block_layout *old_block_layout = (__bridge struct Block_layout *)block;
    if (old_block_layout->invoke == dispatch_block_special_invoke()) {
        wrapped_block = dispatch_block_create(DISPATCH_BLOCK_INHERIT_QOS_CLASS, wrapped_block);
        struct Block_layout *wrapped_block_layout = (__bridge struct Block_layout *)wrapped_block;
        struct dispatch_block_private_data_s *old_dbpds = (struct dispatch_block_private_data_s *)(old_block_layout + 1);
        struct dispatch_block_private_data_s *wrapped_dbpds = (struct dispatch_block_private_data_s *)(wrapped_block_layout + 1);
        if (old_dbpds->dbpd_magic == 0xD159B10C) {
            wrapped_dbpds->dbpd_flags = old_dbpds->dbpd_flags;
            wrapped_dbpds->dbpd_priority = old_dbpds->dbpd_priority;
        }
    }
    dispatch_async(queue, wrapped_block);
}