"Alf P. Steinbach" <alfps@start.no> wrote in message
* Leigh Johnston:
All that's needed is inheritance.
Example? And don't say virtual inheritance.
Please quote enough of the article you're responding to to establish
the necessary context for your response. Not all readers have easy
access to the thread history.
Anyway, you're asking for and doubting the existence of this problem:
#include <assert.h>
struct A
{
int blah;
};
struct B: A
{
virtual ~B() {}
int doh;
};
int main()
{
B* p1 = new B;
A* p2 = p1;
void* pv1 = p1;
void* pv2 = p2;
assert( pv1 == pv2 ); // Uh oh, not guaranteed.
}
To some C++ programmers it comes as a surprise.
Note that the introduction of a virtual destructor in the derived
class is not necessary in order to have this problem, except that with
that it's easier to convince folks since then the assertion fails with
two popular compilers.
Cheers & hth.,
- Alf
Except dynamic_cast<void*>(p2) will not work as A is not polymorphic. :)