FIX: C2985 Error When Template Class Has Static Data Member

ID: Q135536

The information in this article applies to:

Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1, 2.2

SYMPTOMS

A template class that contains a static data member of a type that was not pre-defined, such as a struct or a class, causes this error:


   C2985 <var name> : invalid static data member; template class < template
   class name> already has a function member of the same name.

This error occurs on the line where the static data member is externally declared.

RESOLUTION

Explicitly initialize the static data member when it is declared. This may require adding a constructor to the structure (see the sample code).

STATUS

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

Sample Code


/* Compile options needed: None (compiler defaults will do)
*/ 
struct A {
//   A() {}  // ctor added for explicit initialization
   void some_funct(){}
};
template <class T> struct B {
    static A static_member;
    void func() { static_member.some_funct(); }
};
// error will occur on the following line:

template <class T> A B<T>::static_member /* = A() */ ;

void main()
{
   B<int> b;

   b.func();
}

This code, as shown, generates the error. To work around the problem, change the line where A() is declared and defined from a comment into an executed line, and do the same for the = A() on the line where the error is occurring. This explicitly initializes the data member when it is declared.

Additional query words: 2.00 2.10 2.20 9.0 9.00 9.1 9.10 visualc VC cl

Keywords : kbGenInfo kbLangCPP kbVC
Version : 2.00 2.10 2.20
Platform : NT WINDOWS
Issue type :