[boost] Re: placement 'new' returns pointers with undefinedbehavior

From: David B. Held (dheld_at_[hidden])
Date: 2003-10-11 15:18:33

"E. Gladyshev" <egladysh_at_[hidden]> wrote in message
news:20031011182129.34063.qmail_at_web40807.mail.yahoo.com...
>
> I did it almost the same as in the following example in the
> standard.

This example is in the standard?  Unbelievable.

> [Example:
> struct B {
>   virtual void f();
>   void mutate();
>   virtual ~B();
> };
> struct D1 : B { void f(); };
> struct D2 : B { void f(); };
> void B::mutate() {
>   new (this) D2; // reuses storage -- ends the lifetime of *this
> [...]

You mean to tell me that this exact example is in the
standard?  Where?  First, where does ~B() get called?
Second, how can you be sure in general that *this is the right
size to hold a D2?

Dave

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