question about multi base classes

[Michael]

Hi,

A piece of description about multi inheritance in ISO/ANSI C++ standard is
as following:

A class shall not be specified as a direct base class of a derived class
more than once.
[Note: a class can be an indirect base class more than once and can be a
direct and an indirect base class. ]
Example:

class X { /* ... */ };
class Y : public X, public X { /* ... */ }; // illformed
class L { public: int next; /* ... */ };
class A : public L { /* ... */ };
class B : public L { /* ... */ };
class C : public A, public B { void f(); /* ... */ }; // wellformed
class D : public A, public L { void f(); /* ... */ }; // wellformed

if above class D is OK. why can't the following code be compiled with Visual
C++

#include "stdafx.h"
#include<iostre am>
class v
{};
class b:public v
{};
class e:public v
{};
class d:public b,public v
{};
int main()
{ return 0;}

But the following code work well.

#include "stdafx.h"
#include<iostre am>
class v
{};
class b:public v
{};
class e:public v
{};
class d:public b,public e
{};
int main()
{ return 0;}


thanks in advance
Michael

[John Harrison]

Re: question about multi base classes


"Michael" <michael-chen@sympatico. ca> wrote in message
news:AFu3b.1048 3$nw3.339240@ne ws20.bellglobal .com...[color=blue]
> Hi,
>
> A piece of description about multi inheritance in ISO/ANSI C++ standard is
> as following:
>
> A class shall not be specified as a direct base class of a derived class
> more than once.
> [Note: a class can be an indirect base class more than once and can be a
> direct and an indirect base class. ]
> Example:
>
> class X { /* ... */ };
> class Y : public X, public X { /* ... */ }; // illformed
> class L { public: int next; /* ... */ };
> class A : public L { /* ... */ };
> class B : public L { /* ... */ };
> class C : public A, public B { void f(); /* ... */ }; // wellformed
> class D : public A, public L { void f(); /* ... */ }; // wellformed
>
> if above class D is OK. why can't the following code be compiled with[/color]
Visual[color=blue]
> C++
>
> #include "stdafx.h"
> #include<iostre am>
> class v
> {};
> class b:public v
> {};
> class e:public v
> {};
> class d:public b,public v
> {};
> int main()
> { return 0;}
>
> But the following code work well.
>
> #include "stdafx.h"
> #include<iostre am>
> class v
> {};
> class b:public v
> {};
> class e:public v
> {};
> class d:public b,public e
> {};
> int main()
> { return 0;}
>
>
> thanks in advance
> Michael
>[/color]

Once I'd removed #include "stdafx.h" both your examples compiled with my
copy of VC++ 7.1. The first one produced a warning but that is all.

If you think you've found a compiler bug you should take it up in a VC++
newsgroup (e.g. news:microsoft. public.vc.langu age) and state which version
you are using. Nothing wrong with either code sample that I can see.

john