Make Logger objects thread safe using a mutex.

[svenoaks]

[wackou]

unfortunately, std::mutex comes only with C++11 and Essentia still needs to support older compilers, so it won't be possible to merge that... However you could replace it with an essentia::MutexLocker (https://github.com/MTG/essentia/blob/master/src/essentia/threading.h#L43) and then I would merge it. (an example here: https://github.com/MTG/essentia/blob/master/src/essentia/streaming/phantombuffer.h#L169)

It is better to use the mutexlocker rather that mutex.lock() and mutex.unlock() directly for this reason: http://en.wikipedia.org/wiki/Resource_Acquisition_Is_Initialization

You will also note that at the moment, the implementations for Mutex and MutexLocker are empty, due to the fact that essentia 2.0 only supports running a network in a single-thread. If you wanted to run them multithreaded, you would need to add an #ifdef to threading.h and provide a real implementation for Mutex and MutexLocker (the same as ForcedMutex and ForcedMutexLocker, actually). But the benefits of doing that are unclear, see my comments in your other issue.

[dbogdanov]

Reopening this, as we are C++11 by now.

[LarissaGuder]

There is any update here? I'm having the same issues reported on #798 .

[mijohansen]

Would this fix the annoying [ WARNING ] No network created, or last created network has been deleted... message?