FIX: No Error and Constructor Not Called if Prototype Missing (152055)


The information in this article applies to:

  • Microsoft Visual C++, 32-bit Learning Edition 4.0
  • Microsoft Visual C++, 32-bit Learning Edition 4.2
  • Microsoft Visual C++, 32-bit Enterprise Edition 4.2
  • Microsoft Visual C++, 32-bit Professional Edition 4.0
  • Microsoft Visual C++, 32-bit Professional Edition 4.1
  • Microsoft Visual C++, 32-bit Professional Edition 4.2
This article was previously published under Q152055

SYMPTOMS

If a class declaration does not contain a default constructor declaration, but there is a definition of a default constructor, no error message is generated and the constructor is never called. The problem can be reproduced by building the sample code below.

RESOLUTION

Make sure that each constructor implementation has its prototype in the class declaration.

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: none
   */ 

   #include <iostream.h>

   class MyClass
   {
   public:
      int m_n;
      // No declaration of a default constructor
   };

   MyClass::MyClass() :    // C2600 here.
       m_n (42)
   {
   }

   void main()
   {
       MyClass t;     // Default constructor is not called

       cout << "m_n is " << t.m_n << endl;
       cout << "It should be 42 ";
       cout << "if the correct default constructor was called." << endl;
   }
Visual C++ 5.0 generates the following error when compiling the sample code above:
error C2600: 'MyClass::MyClass' : cannot define a compiler-generated special member function (must be declared in the class first)
Modification Type:MinorLast Reviewed:7/5/2005
Keywords:kbbug kbCompiler kbCPPonly kbfix kbLangCPP kbVC500fix KB152055
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