[Bug c++/33762] New: partial template specialization question

["gzljg at hotmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

Probably this is not a bug, but just I want to make clear to myself...

I have a 'general' template class, and can specialize it for one class(say
base), can I then assume all other classes that derived from 'base' class are
using the specialized version template function(same as the base one)?

Example code:
#include <iostream>
using namespace std;

class Dummy{};
class Base {} ;
class Derive : virtual public Base{};

template <class T> class Stub : virtual public T
{
public:
  Stub() 
  {
    std::cout << "template <class T> class Stub : virtual public T"
              << std::endl;
  }
};

template <> class Stub<Base> 
{
public:
  Stub() 
  {
    std::cout << "template <> class Stub<Base> "
              << std::endl;
  }

};

/*
I have to enable this to make it work as expected, but this is definitely not I
wants, since this mean I had to specialize _all_ the dervied classes like this,
which may be too much....
template <> class Stub<Derive> 
{
public:
  Stub() 
  {
    std::cout << "template <> class Stub<Derive> "
              << std::endl;
  }

};
*/

class A : public Stub<Dummy>
{
};
class B : public Stub<Base>
{
};
class C : public Stub<Derive>
{
};

int main() 
{ 
  A a;  // expected, use the most general template.
  B b;  // expected, use the specialized template since T=Base
  C c;  // ?? I expected it will use the specialized template as well, since
T=Derive, which Derive is derived from Base.    Am I wrong here??
  return 0;
}


program output:
template <class T> class Stub : virtual public T
template <> class Stub<Base> 
template <class T> class Stub : virtual public T   // I expected should be "
template <> class Stub<Base>" as above here.


-- 
           Summary: partial template specialization question
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: gzljg at hotmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33762