Re: ambiguity in diamond inheritance

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Sat, 8 Mar 2008 02:00:51 -0800 (PST)
Message-ID:
<74942052-8ca6-4e96-9f03-68cf6a188c97@u72g2000hsf.googlegroups.com>
On 8 mar, 08:57, karthikbalaguru <karthikbalagur...@gmail.com> wrote:

On Mar 7, 6:11 pm, Pete Becker <p...@versatilecoding.com> wrote:

On 2008-03-06 23:34:45 -0500, karthikbalaguru
<karthikbalagur...@gmail.com> said:

I understand the Diamond Problem and the solution of
"Virtual Inheritance" that is used to overcome ambiguity.
But, i wonder why should the Diamond problem arise. This
should be taken care by C++ internally and resolved. Why
C++ could not handle it internally without asking us to do
the 'virtual inheritance'?


"The Diamond Problem" arises because the writer of a class
hierarchy didn't understand how inheritance works.

struct A
{
int i;
};

struct B : A
{
};

struct C : A
{
};

struct D : B, C
{
void f();
};

void D::f()
    {
    i = 3; // error: ambiguous
    }

There are two separate "i" members in D. There's no way the
compiler can "handle it internally".


But, Why is the compiler unable to handle it internally ?


Handle what? How is the compiler supposed to know which i
(B::A::i or C::A::i) you want to refer to?

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