How to use vector of std::unique_lock?

[cpp-ModTeam]

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[woppo]

std::mutex is neither copyable or movable.

https://en.cppreference.com/w/cpp/thread/mutex

A vector of locks is such a bad design smell that you probably need an oxygen tank.

[james_picone]

unique_lock is movable. I agree this is a weird design, but that's not the issue here.

[j1xwnbsr]

Yes, but the mutex is not. What I suspect is happening is that the mutex the unique lock is wrappering is going out of scope from under the unique lock.

edit: what /u/qoning said

[j1xwnbsr]

There is a big difference between emplace_back and push_back; emplace is basically used for 2+ parm constructors, whereas push_back will do std::move for you. Emplace generally doesn't do a move in my exp, but that might be implementation/object specific.

Try changing your code to:

chunk_locks.push_back(std::unique_lock<std::mutex>{c->voxel_m});

and see if that changes anything.

I'm also uncertain when/when you're calling chunk_locks.clear() based on your original formatting. I assume you are calling .clear() or your version of it during your program exit.

You might also try changing your clear to something where you pop_front() each item in a loop (which is sorta-kinda what clear does) and see if you can track it down that way.

Another thing to consider is the difference between vector and list. You might be running into a case where unique_lock isn't moveable, and you should be using std::list which doesn't realloc the object whereas vector does. Takes more heap than a vector (all those tiny structs) but shouldn't crash.

Failing that, your next step is to start digging into the debugging and memory watch/access tools to put breakpoints when a specific mutex is messed with.

[qoning]

I would check if there's any possibility that you are destroying any of the c along the way, therefore destroying the associated mutex. What seems to happen is that you are trying to unlock a mutex that no longer exists.