Indeed. Richard's messages make me a little uneasy about just what does begin the lifetime of a POD object, though. I'm thinking of:

  struct B { int x; };  // 1

  void* p = malloc(sizeof(B)); // 2

  B* pb = static_cast<B*>(p); //3

  pb->x = 17; // 4

I take it as obvious that the lifetime of an object of type B has begun somewhere in this code snippet. Now the question is: which specific line begins that lifetime? As you say, casting a pointer doesn't begin or end a lifetime; I think we can rule out line 3 as the one that begins the lifetime of that B object. Line 1 doesn't look too promising either.

A literal reading of the standard ([basic.life]/1) suggests that it's line 2: 

"The lifetime of an object of type T begins when:

— storage with the proper alignment and size for type T is obtained, and

— if the object has non-trivial initialization, its initialization is complete."

In line 2 we have obtained storage with the proper alignment and size for type B, and the second bullet item doesn't apply since B has no non-trivial initialization. None of the other lines are relevant to the beginning of the lifetime.

But that's a little disturbing too. If we've got:

  struct X { int x; }; // 1'

  struct Y { int y; };  // 2'

  void* p = malloc(sizeof(X));  // 3'

then does line 3' mean that the lifetime of some object has begun? Again a literal reading of that same standard text suggests yes. We have obtained storage with the proper alignment and size for type X, so the lifetime of an object of type X has begun. Exactly the same argument means that the lifetime of an object of type Y has begun, and similarly for every other type, mentioned or not, whose size is equal to sizeof(X).

That seems like a crazy conclusion, but I don't see how to reject it without also rejecting the idea that the lifetime of an object of type B has been established somewhere in my first code snippet. What all of this suggests to me is that the concept of object lifetime needs a little more thought for types that don't have initialization.

                         --Matt