FIX: C2974 Error When Calling Templated Base Class Functions

• Microsoft C/C++ Compiler (CL.EXE), used with:
  • Microsoft Visual C++ 32-bit Edition, versions 2.0, 2.1

SYMPTOMS

Calling a member function of a templated base class through the 'this' pointer produces the following erroneous error:

error C2974: '<base templated class name>' : invalid template actual argument '#1', type expected.

RESOLUTION

Call the function without using the 'this' pointer.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This problem was fixed in Microsoft Visual C++, 32-bit Edition, version 4.0.

MORE INFORMATION

The Visual C++ compiler generates the following errors when the following sample program (TEST.CPP), is compiled with the /D"SHOW_TEMPLATE_ERROR" option:

test.cpp(20) : error C2974: 'A' : invalid template actual argument '#1',
               type expected
test.cpp(20) : error C2231: '.B<int,int>::A<int>::Afunc' : left operand
               points to 'class', use '->'
test.cpp(20) : fatal error C1903: unable to recover from previous
               error(s); stop ping compilation 

Sample Code to Demonstrate Problem

/* Compile options needed: none
*/ 
// #define SHOW_TEMPLATE_ERROR

template <class Type>
class A
{
public:
    Type a;
    void Afunc(void){};
};

template <class Type1, class Type2>
class B: public A<Type1>
{
public:
    void Bfunc()
    {
#ifdef SHOW_TEMPLATE_ERROR
        this->A<Type1>::Afunc();
#else
        A<Type1>::Afunc();
#endif
    }
};

void main()
{
    B<int, int> b;
} 

Additional query words: 2.00 2.10

Keywords : kbCompiler kbCPPonly kbVC
Version : :2.0,2.1
Platform : NT WINDOWS
Issue type :