Re: Partial template specialization with a reference as a parameter - compilation problem

From:

Victor Bazarov <v.Abazarov@comAcast.net>

Newsgroups:

microsoft.public.vc.language

Date:

Wed, 08 Oct 2008 16:09:33 -0400

Message-ID:

<gcj41t$tpe$1@news.datemas.de>

ferland.francois@gmail.com wrote:

I'm having a problem while using references as template parameters and
partial specialization. Here's a simplified case where it doesn't work
(with VC++ Express 2008) :

----

#include <iostream>

int C;

template<class A, int& B>
class D
{
    D()
    {
        std::clog << "Base." << std::endl;
    }
};

template<int& B>
class D<char, B>
{
    D()
    {
        std::clog <<"Special: char." << std::endl;
    }
};

int main(int argc, char** argv)
{
    D<int, C> d1;
    D<char, C> d2;

    return 0;
}

----

This should produce two lines: "Base." and "Special: char.". However,
I get "Base." two times, which means the specializing didn't get
picked up. If I replace the reference by a pointer (or anything else),
it works correctly. While using a pointer would be an OK workaround,
I would really prefer to keep using references, since it compile
correctly in GCC and is our main compiler. I couldn't test it with
other VC++ versions.

Anybody has any clues on how to fix this? Is this a recognized bug? I
looked around but couldn't find anything.

AFAICT, it's a bug in the compiler. Here is the source which you can
put in when you submit a bug report:
=========================================
template<class A, int& B>
struct D
{
     void foo(){}
};

template<int& B>
struct D<char, B>
{
private:
     void foo() {}
};

int C;

int main()
{
     D<int, C> d1;
     D<char, C> d2;

     d1.foo();
     d2.foo(); // should be error - compiles OK, apparently not
               // picking up the specialization
}
=========================================

Comeau online trial version reports the error correctly.

V
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