Call to make pair with mutex as argument fails. Cannot insert mutex onto unordered map

std::mutex is not copyable or moveable. When you do

std::mutex mtx;
auto t = std::make_pair(std::string("hello"), mtx);

and

mHeartBeatMutexes.insert(std::make_pair(std::string("hello"), mtx));

std::make_pair tries to make a copy of mtx since it is an lvalue and it can't because std::mutex is not copyable.

In

std::mutex mtx;
auto t = std::make_pair(std::string("hello"), 1);

1 is an integer literal which materializes into a temporary integer that is moved (copy really as it's the same thing) and that's all good.

To put a mutex into a std::unordered_map<std::string, std::mutex> what you need to do is use the emplace function to directly create the pair inside the unordered_map leverage the std::piecewise_construct overload and std::forward_as_tuple to build the arguments for each member of the pair's constructor like

std::unordered_map<std::string, std::mutex> foo;
foo.emplace(std::piecewise_construct,
            std::forward_as_tuple("hello"),
            std::forward_as_tuple());