How to easily make std::cout thread-safe?

Question

I have a multi-threaded application, which heavily uses std::cout for logging without any locking. In such a case, how can I easily add lock mechanism to make <

Answer 1

I really like the trick from Nicolás given in this question of creating a temporary object and putting the protection code on the destructor.

/** Thread safe cout class
  * Exemple of use:
  *    PrintThread{} << "Hello world!" << std::endl;
  */
class PrintThread: public std::ostringstream
{
public:
    PrintThread() = default;

    ~PrintThread()
    {
        std::lock_guard guard(_mutexPrint);
        std::cout << this->str();
    }

private:
    static std::mutex _mutexPrint;
};

std::mutex PrintThread::_mutexPrint{};

You can then use it as a regular std::cout, from any thread:

PrintThread{} << "my_val=" << val << std::endl;

The object collect data as a regular ostringstream. As soon the coma is reached, the object is destroyed and flush all collected information.