A Brief Refresher on Member Initialization

So, I forgot something that is maybe a little important, especially when it comes to multithreaded code.

struct MakeThreads
{
    MakeThreads() :
    _thread(threadFunc, this)
    , _done(false)
    {
    }
    ~MakeThreads()
    {
        _done = true;
        _thread.join();
    }

    void threadFunc()
    {
        while(!_done)
        {
            // do stuff
        }
    }

    Thread  _thread;
    bool    _done;
}

MakeThread letsScrewUp;

Now, my old, single-threaded, C self wants to put the smaller members later in the struct/class declaration to ensure data packing is efficient. My new, multi-threaded C++ self hasn't formed proper habits to prevent this sort of bug. How I wish I had lint here to continue to wrap my knuckles and improve my coding habits!

Just a reminder, the member initializer list in the constructor does NOT dictate the order in which members are initialized with many C++ compilers. As Scott Meyers (and g++ with proper settings) warns us: the member initializer list should always match the order of member declaration in a class!

I made this mistake recently. For those that haven't already caught it, _done is initialized AFTER the thread is initialized. The thread queries _done (which may or may not be initialized at this point.)

This is one of those scenarios where the code does what you expect most of the time but rarely all of the time!

Like any language, some of the finer points of C++ are easy to forget unless you find opportunities to practice them often. For those itches that aren't scratched on your day job, I highly recommend busting your own chops in your spare time for remedial work :)