Thread-safe static variables without mutexing?

Question

I remember reading that static variables declared inside methods is not thread-safe. (See What about the Meyer\'s singleton? as mentioned by Todd Gardner)

Dog* M         


        

Answer 1

One way you could do it that does not require a mutex for thread safety is to make the singleton a file static, rather than function static:

static Dog dog("Lassie");
Dog* MyClass::BadMethod()
{
  return &dog;
}

The Dog instance will be initialised before the main thread runs. File static variables have a famous issue with the initialisation order, but as long as the Dog does not rely on any other statics defined in another translation unit, this should not be of concern.