dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

I'm struggling with some problems in the implementation of automatic
update/interpolation during mesh refinement.

I've narrowed one of the problems down to the following simple
example. Say that a class C inherits from both A and B (which both
have member variables - this is important). Then I would expect an
object c of class C to have the same address/pointer as seen from all
three classes. But what happens is that A and C (if C inherits from A
first) agree on the address, but not B.

Try the following simple code:

#include <iostream>
using namespace std;

class A
{
public:
  A() { cout << "A pointer: " << this << endl; }
  int avar;
};

class B
{
public:
  B() { cout << "B pointer: " << this << endl; }
  int bvar;
};

class C : public A, public B
{
public:
  C() { cout << "C pointer: " << this << endl; }
};

int main()
{
  C c;

  A* a = &c;
  B* b = &c;

  cout << "&a = " << a << endl;
  cout << "&b = " << b << endl;
  cout << "&c = " << &c << endl;

  return 0;
}

The output when running the program is something like this:

A pointer: 0x7fff89a97a50
B pointer: 0x7fff89a97a54
C pointer: 0x7fff89a97a50
&a = 0x7fff89a97a50
&b = 0x7fff89a97a54
&c = 0x7fff89a97a50

Any ideas why this happens?

--
Anders

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