error C2761 member function redeclaration not allowed

Question

I've encountered a problem(error C2761) while writing specializations for a class. My classes are as follows:

class Print{
public:
    typedef class fontA;
    typedef class fontB;
    typedef class fontC;
    typedef class fontD;

    template<class T>
    void startPrint(void) { return; };
    virtual bool isValidDoc(void) = 0;
};

I have a class QuickPrint which inherits the Print class:

class QuickPrint : public Print {
       ...
};

The error occurs when I try to write specializations for the startPrint method:

template<>        // <= C2716 error given here
void QuickPrint::startPrint<fontA>(void)
{
      /// implementation
}

template<>        // <= C2716 error given here
void QuickPrint::startPrint<fontB>(void)
{
     /// implementation
}

The error appears for the remaining specializations as well.

score 1 · Accepted Answer · answered Aug 12 '12 at 20:31

1

QuickPrint does not have a template member function named startPrint, so specializing QuickPrint::startPrint is an error. If you repeat the template definition in QuickPrint the specializations are okay:

class QuickPrint : public Print {
   template<class T>
    void startPrint(void) { return; };
 };

template<>        // <= C2716 error given here
void QuickPrint::startPrint<Print::fontA>(void)
{
      /// implementation
}

But if the goal here is to be able to call into QuickPrint polymorphically, you're in trouble, because the template function in Print can't be marked virtual.

answered Aug 12 '12 at 20:31

Pete Becker

74,985
8
76
165

Thanks, adding the default implementation into the derived class worked. – Sebi Aug 12 '12 at 20:38
That appears to be dangerous. If now some function of `Print` calls `startPrint`, the specialization he wrote is not chosen because he didn't specialize Print's member function template. – Johannes Schaub - litb Aug 12 '12 at 20:40
Yes, that's what I said; it's not polymorphic. – Pete Becker Aug 12 '12 at 20:43

score 0 · Answer 2 · answered Aug 12 '12 at 20:35

0

try this:

class QuickPrint : public Print {
    template<class T>
    void startPrint(void) { Print::startPrint<T>(); };
};

answered Aug 12 '12 at 20:35

Gir

839
5
11

score -1 · Answer 3 · answered Aug 12 '12 at 20:22

Your issue is this line:

template<class T> 
void startPrint(void) { return; };

You already provide a function body, but then try to redefine it again (using specialization), which won't work.

Remove that function body and it should work.

To define a default behaviour, provide a default value for template paramter T and then add a single specialization for that one.

error C2761 member function redeclaration not allowed

3 Answers3

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