Using boost::bind with a class containing a boost::mutex

Question

I'm working on a server using a watchdir to add items to an internal collection. The watchdir is browsed periodically by a thread which is created like this :

this->watchDirThread = new boost::thread(boost::bind(&Filesystem::watchDirThreadLoop,
                                                      this,
                                                      this->watchDir,
                                                      fileFoundCallback));

The fileFoundCallback parameter is also created via boost::bind :

boost::bind(&Collection::addFile, this->collection, _1)

I would like to protect my collection from concurrent access using a mutex but my problem is that the boost::mutex class is non copyable, therefore there can't be a mutex in my Collection class since boost::bind requires copyable parameters.

I don't like the idea of a static mutex because it would be semantically wrong as the role of the mutex here is to prevent my collection to be read while it's being modified.

What can I do to solve this problem ?

Answer 1

Use std::ref or std::cref around the mutex. That is, instead of:

boost::mutex yourmutex;
boost::bind(..., yourmutex, ...);

write:

boost::mutex yourmutex;
boost::bind(..., std::ref(yourmutex), ...);