FIX: C2065 Error on Functions Returns Template Class By Value

The information in this article applies to:

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

SYMPTOMS

Any reference to a template function that returns a template class by value generates these errors:

   error C2065: 'function name' : undeclared identifier
   error C2064: term does not evaluate to a function C2065

RESOLUTION

Modify the function to return a reference to the template class instead of returning by value. In the "Sample Code" section of this article, function

'f1' returns a template class by value and fails. Function 'f2' returns a

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

Sample Code

/* Compile options required: none
*/

   T m;

template<class T> M<T> f1(const M<T>& x) {return x;}

template<class T> M<T>& f2(const M<T>& x) {return x;}

void test(void)

   M<int> x;
   M<int> y = f1(x);  // errors C2065 & C2064
   M<int> z = f2(x);  // no error

NOTE: Although this has been fixed under Visual C++ 4.0, the definition of function f2:

   template<class T>
   M<T>& f2(const M<T>& x) {return x;}

   error C2446: [*] 'return' : no conversion from 'const class M<int>' to
'class M<int> &' (new behavior; please see help)
   error C2561: 'f2' : function must return a value

   M<T>& f2(const M<T>& x) {return (M<T>&)x;}