Re: object lifetime

 James Kanze <>
Fri, 20 Jul 2007 08:58:52 -0000
On Jul 19, 6:02 pm, REH <> wrote:

I've been trying to better understand the subtle rules for object
lifetime. The standard says that pointers to the memory of a
dynamically allocated object may be used in limited ways after the
object's destructor has executed (but the memory not deallocated).
Specifically, the pointer must be a void*.

There's no strict requirement that it be converted to void*. As
long as the memory has not been freed, you can copy and compare
the pointer all you want; you can only dereference if you
convert it to a pointer to character type, and access the
underlying bytes as char or unsigned char.

Does that mean, the following is well defined?

As written, yes, but only because T is the most derived class.

#include <new>

class T {};

int main()
    T* p = new T();
    operator delete(static_cast<void*>(p));

You don't need the static_cast here; in fact, it doesn't change

This is legal as long as p pointed to the most derived object
initially. If you'd written something like:

    Base* p = new Derived ;
    // ...
    p->~Base() ;
    operator delete( p ) ;

Then the behavior would be undefined.

    return 0;

James Kanze (GABI Software)
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