BUG: You receive a "fatal error C1001: INTERNAL COMPILER ERROR" error when you create an object that is a copy of a virtual function return value in Visual C++ 6.0 (226110)

The information in this article applies to:

Microsoft Visual C++, 32-bit Enterprise Edition 6.0
Microsoft Visual C++, 32-bit Professional Edition 6.0
Microsoft Visual C++, 32-bit Learning Edition 6.0

This article was previously published under Q226110

SYMPTOMS

When creating an object that is a copy of a virtual function return value (a temporary object) using the compiler-supplied copy constructor, you may get the following error:

test.cpp(22) : fatal error C1001: INTERNAL COMPILER ERROR
(compiler file 'msc1.cpp', line 1794)
Please choose the Technical Support command on the Visual C++
Help menu, or open the Technical Support help file for more information

Please see the steps to reproduce in the More Information section below.

RESOLUTION

There are four ways to get around the problem:

Explicitly Define a Copy Constructor. (See Workaround #1 in sample code below).
Remove the virtual keyword from the function which returns the value. (See Workaround #2 in sample code below).
Introduce a temporary variable to store the return value. (See Workaround #3 in the sample code below).
Remove compiler support for synchronous (C++) exception handling. This is accomplished by removing /GX (the Visual Studio default) from your compile options. (See Workaround #4 in sample code below).

Workaround #1 is the recommended workaround whenever possible.

NOTE: If you define a copy constructor, you should also define an assignment operator (operator=).

STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.

This problem was corrected in Microsoft Visual C++ .NET.

MORE INFORMATION

////////////////////////////////////////////////////////////////////// 
// cl /c /GX test.cpp
// test.cpp(22) : fatal error C1001: INTERNAL COMPILER ERROR
//  (compiler file 'msc1.cpp', line 1794) 
//  Please choose the Technical Support command on the Visual C++ 
//  Help menu, or open the Technical Support help file for more information
////////////////////////////////////////////////////////////////////// 
class A
{
  public:
    /* workaround #1, add an explicit copy constructor to class A */ 
    // A(A& a) {};
    ~A() {}; 
};
class B
{
  public:
 /* workaround #2, remove virtual keyword from B::GetA */ 
    virtual A& GetA(void);
    void Func (void);
};
void B::Func (void)
{
  A *att;
  att=new A(GetA());
  /* workaround #3, substitute the above line with the following two lines */ 
  //A tmp = GetA();
  //att=new A(tmp);
}
/* workaround #4, remove /GX compiler option */

Modification Type:	Major	Last Reviewed:	4/28/2005
Keywords:	kbtshoot kberrmsg kbBug kbCompiler kbfix kbNoUpdate KB226110 kbAudDeveloper