From: Felipe Magno de Almeida
On 10/30/06, Anthony Williams <anthony_w.geo@yahoo.com> wrote:
Roland Schwarz <roland.schwarz@chello.at> writes: [snipped]
Do you mean: the object might be already zero initialized before the ctor runs? If yes: this is very dangerous to rely on!
No. This is required. The memory for an object with static-storage-duration MUST be zero initialized prior to the constructor running.
It dont even matter, it *must* not have a constructor. Or else there'll be a race condition on the compiler's flag and multiple constructor calls.
Does this matter if all the constructor does is repeat the zero initialization? (Serious question. The answer is not obvious to me). Roland suggested a mutex which relied on the zero initialization of static PODs. He then listed a number of issues that maintaining POD status introduces (like we can't eliminate copy constructors). I pointed out that actually ALL static objects are zero initialized, so we could have a default constructor that does nothing or repeats the zero initialization (which means we could create the mutex other than as a object with other than static storage duration). -- Martin Bonner Martin.Bonner@Pitechnology.com Pi Technology, Milton Hall, Ely Road, Milton, Cambridge, CB24 6WZ, ENGLAND Tel: +44 (0)1223 203894