# V1018. Usage of a suspicious mutex wrapper. It is probably unused, uninitialized, or already locked.

The analyzer has detected an incorrect use of a mutex wrapper (std::unique_lock, etc).

Consider the following example:

    std::unique_lock<std::mutex> lck;
    lck.lock();

Here, in the second line, an exception 'std::system_error' will be thrown since there is no mutex associated with the wrapper. It should either be passed in the constructor:

    std::unique_lock<std::mutex> lck(m, std::defer_lock);
    lck.lock();

or initialized by the 'swap()' method:

    std::unique_lock<std::mutex> lck_global(mtx, std::defer_lock);
    ....
    std::unique_lock<std::mutex> lck;
    lck.swap(lck_global);
    lck.lock();

This diagnostic also detects cases where a critical section is declared but the mutex is not locked for some reason:

    std::unique_lock<std::mutex> lck(m, std::defer_lock);
    //lck.lock();

This diagnostic is classified as:

CWE-413 CWE-833