FIX: C2084 When Template Class Constructor Has No Body
ID: Q150573
|
The information in this article applies to:
-
The C/C++ Compiler (CL.EXE), included with:
-
Microsoft Visual C++, 32-bit Editions, versions 4.1, 4.2
SYMPTOMS
The following error occurs when a template class is explicitly instantiated
and it has more than one constructor, at least one of which does not have a
body defined and at least one of which is defined outside of the class:
error C2084: function '<function name>' already has a body
WORKAROUND
This is the preferred workaround. Give every constructor a body. The
body is defined inside or outside the template class.
-or-
- Place all the existing constructor bodies inside the template class
definition.
NOTE: You get the following warning associated with the explicit
instantiation request:
warning C4661: <symbol> : no suitable definition provided for
explicit instantiation request
This warning is issued when a template class does not have all its
members defined and an explicit instantiation request is made. This
warning also causes the compiler to ignore the instantiation request.
-or-
- Instantiate the template class implicitly rather than explicitly. In
this case, the instantiation occurs when declaring an object using the
template class, but the C2084 does not.
NOTE: the sample code in this article gives examples of explicit versus
implicit template instantiation.
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 Visual C++
version 5.0.
MORE INFORMATION
Sample Code
/* Compile options needed: /c
*/
template <class T>
class A {
public:
A(); // give this ctor a body for workaround 1
A(const T&);
};
template <class T> A<T>::A(const T&) {}; // move this ctor body
// inside the class
// definition for
// workaround 2
template A<int>; // this is an explicit instantiation -
// comment this line out and uncomment the
// next line for workaround 3
// A<int> x = 3; // this is an implicit instantiation
Additional query words:
kbVC400bug
Keywords : kbCompiler kbCPPonly kbVC kbVC500fix
Version : 4.1 4.2
Platform : NT WINDOWS
Issue type : kbbug