Re: Calling virtual method of base class nested in template class (VC++ 6.0)
Actually, I came up with a simpler example that exhibits the same bug (no
template, and nesting at only a single level):
#include <iostream>
class B
{
public:
B( ) { }
class N1
{
public:
N1( ) { };
virtual void f( )
{
std::cout << "B< >::N1::f( )" << std::endl;
}
};
};
class D : public B
{
public:
class N1 : public B::N1
{
public:
N1( ) : B::N1( ) { };
virtual void f( )
{
typedef B::N1 BN1;
std::cout << "D::N1::f( )" << std::endl;
BN1::f( );
}
};
};
void
main( int argc, char* argv[ ] )
{
D::N1 n1;
n1.f( );
}
However, the problem is worked around by changing the name of D::N1 to
something other than N1. Apperently, the VC6.0 compiler becomes confused as
to which N1 I was referring and just assumed the most derived N1, rather
than the one specified by the typedef (i.e., the N1 in B).
When I renamed N1 to, say, Joe, it worked.
"Roger" <someone@idontwantspam.com> wrote in message
news:KNWIg.4215$yO7.3921@newssvr14.news.prodigy.com...
Hi all.
Here's a little quandry I've run in to and can't tell if it's a compiler
bug, or if it's bad code. First, here's the code:
===================================
#include <stdio.h>
template < typename T >
class B
{
public:
B( ) { }
class N1
{
public:
N1( ) { };
class N2
{
public:
N2( ) { };
virtual void f( )
{
printf( " B< >::N1::N2::f( )\n" );
}
};
};
T _m;
};
class D : public B< int >
{
public:
class N1 : public B< int >::N1
{
public:
N1( ) : B< int >::N1( ) { };
class N2 : public B< int >::N1::N2
{
public:
N2( ) : B< int >::N1::N2( ) { };
virtual void f( )
{
typedef B< int >::N1::N2 Bint; // must do this to avoid VC6.0's
"error C2352: 'B<int>::N1::N2::f' : illegal call of non-static member
function" bug.
printf( " D::N1::N2::f( )\n" );
// B< int >::N1::N2::f( ) causes the compiler to complain (see
typedef above). However, VC7.1 works fine.
Bint::f( );
}
};
};
};
void
main( int argc, char* argv[ ] )
{
D::N1::N2 n2;
n2.f( );
}
==================================
Invoking n2.f( ) causes an infinite loop, dumping out "D::N1::N2::f( )"
ad-nausium. I am trying to call the base-class f( ) in B::N1::N2, but the
VC6.0
compiler just generates code that instead calls D::N1::N2::f( )
recursively.
VC7.1 compiles this just fine (even on the commented out line).
What am I doning wrong? Or, is this a compiler bug?
If it's a bug, is there a fix or how can I call the base's f( )?
BTW: I'm stuck w/VC6.0, so please don't suggest using VC7.1; thanks.
Thanks for any help you can offer!
- Roger