Question

Given:

void getBlah() {
  static Blah* blah = new Blah();
  return blah;
}

In a multi threaded setting, is it possible that new Blah() is called more than once?

Thanks!

Answer 1

The C++ standard makes no guarantee about the thread safety of static initializations – you should treat the static initialization as requiring explicit synchronisation.

The quote Alexander Gessler gives:

If control enters the declaration
concurrently while the object is being
initialized, the concurrent execution
shall wait for completion of the
initialization

is from the C++0x draft, and doesn’t reflect the current C++ standard or the behaviour of many C++ compilers.

In the current C++ standard, that passage reads:

If control re-enters the declaration (recursively) while the object is being
initialized, the behaviour is undefined