SyncPoint

SyncPoint is pasted from https://github.com/facebook/rocksdb/blob/main/test_util/sync_point.h . It's very helpful when testing multi-thread programs.

Here are some differences from rocksdb::SyncPoint:

• No KillPoint
• No BloomFilter in SyncPoint
• Namespace is different

Thanks rocksdb!

Notice

You'd better not throw exception in SyncPoint, because it's not exception safety:

    auto callback_pair = callbacks_.find(point_string);
    if (callback_pair != callbacks_.end()) {
        num_callbacks_running_++;
        mutex_.unlock();
        callback_pair->second(cb_arg);
        mutex_.lock();
        num_callbacks_running_--;
    }
    cleared_points_.insert(point_string);
    cv_.notify_all();

If you throw exception in callback, it will throw exception without dec num_callbacks_running_.