BUG: Member Function Referenced Without () Compiles

ID: Q155046

The information in this article applies to:

Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1, 4.2, 5.0, 6.0

SYMPTOMS

Leaving the parentheses off a member function call, or leaving the ampersand ("&") off a reference to a pointer to a member function, does not result in a compiler error.

CAUSE

In both cases, the Visual C++ compiler is incorrectly treating the reference as a pointer to the member function. A pointer to a member function cannot be referenced via a specific instance of a class (for example, "obj.MyFunct" in the sample code below). Instead, it must be referenced via the class name, scope operator and '&' operator (for example, &CMyClass::MyFunc in the sample code below).

RESOLUTION

The compiler should report an error on the line in question.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

Sample Code


/* Compile options needed:
*/ 


class CMyClass
{

  public:

  void MyFunc() {int nVar = 100; }
};


void main()
{
  CMyClass obj;

  obj.MyFunc();  //Correct syntax - calls the member function
  obj.MyFunc;    //Typo, no (), should result in error but doesn't
                 //VC 5.0: correct warning C4551
  CMyClass::MyFunc;  // Typo, no &, should result in error but doesn't
  &CMyClass::MyFunc; // Correctly treated as a pointer to member
                     // function.
}

Note that executing the program generated by the above code causes no run- time errors, but executes MyFunc only once. The incorrect line has no affect because it is treated exactly the same as the line following it.

Also note that this problem could seem to cause incorrect execution paths if the parenthesis are left off accidentally in the following type of construct:


   if (obj.MyFunc) {   // Should be an error, instead always evaluates to
                       // TRUE. This code always executes.
   }
   else {
       // This code will never be reached.
   }

Additional query words: kbVC420bug kbVC400bug


Keywords          : kbCodeGen kbCompiler kbCPPonly kbVC kbVC400bug kbVC410bug kbVC420bug kbVC500bug kbVC600bug 
Version           : winnt:4.0,4.1,4.2,5.0,6.0
Platform          : winnt 
Issue type        : kbbug

Last Reviewed: May 17, 1999