Sigh... yes that's why we *still* don't have a singleton in Boost.
And somehow, I like we dont have any public singleton class. I know what happens when you give singleton to people: they use it everywhere ;)
That was what I was hinting at - I had assumed that use of Boost.Thread's call_once was the only way to do this right, and then I saw the code and wasn't so sure.
The thing I'm concerned about is this:
* The code currently relies on a call to a function in a static object to force that object to be instantiated and initialize the singleton, but: * Once compiler optimizations are turned on, that function call will be optimized away to a no-op. * There's now no code that's using the global object. * A clever linker says "hey we don't need this anymore" and removes it from the program image, so: * The singleton no longer gets initialized before main starts (only when it's first called).
Of course this optimization changes program behavior so it ought to be forbidden... but you know I'm paranoid ;-)
Being paranoid here is actually the sane thing. I think having a pointer based singleton with compare-and-swap initailisation is probably better. IIRC there is such a beast in Modern C++ design and Loki but I dunno how OK it is.