Microsoft KB Archive/152055

= FIX: No Error and Constructor Not Called if Prototype Missing =

Article ID: 152055

Article Last Modified on 7/5/2005

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APPLIES TO


 * Microsoft Visual C++ 5.0 Learning Edition
 * Microsoft Visual C++ 5.0 Learning Edition
 * Microsoft Visual C++ 4.2 Enterprise Edition
 * Microsoft Visual C++ 4.0 Professional Edition
 * Microsoft Visual C++ 4.1 Subscription
 * Microsoft Visual C++ 4.2 Professional Edition

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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.



Sample Code
/* Compile options needed: none */

#include 

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)

Additional query words: kbVC400bug

Keywords: kbbug kbfix kblangcpp kbvc500fix kbcpponly kbcompiler KB152055

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