I am trying to simplify code in the SFML library ensuring that the first created object of type AudioResource initializes an audio device, and that the last destroyed object deinitializes it.

As I believe that the current solution using std::shared_ptr and std::weak_ptr is overkill, I came up with a simpler alternative using a static global variable. Here’s a simplified version (the real one is protected by std::mutex, see PR link above):

// AudioResource.hpp --------------------------------

struct AudioResource
{
     AudioResource();
    ~AudioResource();
    // ...
};

// AudioResource.cpp --------------------------------

#include "AudioResource.hpp"

static int deviceRC = 0;

 AudioResource() { if (deviceRC++ == 0) { /* init device   */ }; }
~AudioResource() { if (--deviceRC == 0) { /* deinit device */ }; }
// ...

I’m quite sure that the code above is fine and not subject to static order initialization fiasco, as the deviceRC global static variable is defined only in AudioResource.cpp and only accessed in that same TU.

My understanding is that, as long as there are no dependencies between multiple global static variables from different TUs, there’s no risk here whatsoever.

Is my understanding correct, or is it possible that the code above results in undefined behavior by accessing an uninitialized deviceRC somehow?

Is it possible that there is some weird scenario where creating AudioResource objects from multiple TUs or when using SFML as a shared library can cause problems with this particular incantation?

Is it correct to say that it’s safe even if deviceRC does not get constant-initialized?

Other maintainers of SFML have been adamant in suggesting the use of a function-scope static variable here:

// AudioResource.cpp --------------------------------

#include "AudioResource.hpp"

static int& deviceRC() 
{
    static int result = 0;
    return result;
}

 AudioResource() { if (deviceRC()++ == 0) { /* init device   */ }; }
~AudioResource() { if (--deviceRC() == 0) { /* deinit device */ }; }
// ...

However, I think that doesn’t make the code any safer nor it is necessary. Am I correct, or is the fuction-scope static variable here necessary?