"Chris Thomasson" <cristom@comcast.net> writes:
once() throw() : m_state(0), m_count(1) {}
static atomic::once<foo> g_foo;
void some_threads(...) { for(;;) { // whatever...
foo *myfoo = g_foo.load(); if (myfoo) { // use myfoo...
// okay, we are finished with myfoo g_foo.dec(); }
} }
This should be a workable solution to the static initialization problem...
What do you all think?
your once<> class has a constructor, so it is therefore dynamically initialized, rather than statically, so there is a potential race condition in calling the constructor. Not only might multiple threads run the constructor, but some threads might get on to the load() call before the constructor is complete, because the constructor is running in another thread. Oh, and if the constructor is run multiple times, when is the destructor called, and how many times? This is particularly apparent in void some_thread_func() { static atomic::once<foo> g_foo; foo *myfoo = g_foo.load(); if (myfoo) { } } since g_foo won't be initialized until the first call. The problem still exists for global objects, but is rarer, since it will only happen with threads that run before main(), or as a consequence of the general global-initialization-order problem, which is independent of threads. Anthony -- Anthony Williams Software Developer Just Software Solutions Ltd http://www.justsoftwaresolutions.co.uk