FIX: /Od May Generate Destructor for Unconstructed Temp Object (168010)

The information in this article applies to:

Microsoft Visual C++, 32-bit Enterprise Edition 5.0
Microsoft Visual C++, 32-bit Professional Edition 5.0

This article was previously published under Q168010

SYMPTOMS

The destructor for a class may be called for an unconstructed temporary when used with the conditional operator.

RESOLUTION

Use an if-else construct in lieu of the conditional operator. In most cases, the logical not operator can be applied to the first operand while reversing the second and third operands.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been corrected in Visual Studio 97 Service Pack 1.

For additional information about the Visual Studio 97 Service Pack 1, please see the following article in the Microsoft Knowledge Base:

170365 Visual Studio 97 Service Packs - What, Where, and Why

MORE INFORMATION

Assuming a class C and a type T, the following conditions must be true of the ternary expression for this bug to occur:

The second operand is of type C.
The third operand is of type T.
Class C has an operator T() and a constructor, C(T).

The following sample demonstrates the problem.

Sample Code

   typedef int T;
   class C
   {
       T _i;
   public:
       C(const C& c);
       C(T);
       ~C();
       operator T();
   };
   void f(T i)
   {
       C c1(5);
       C c2 = i==0 ? c1 : i;
            //i ? i : c1; // possible workaround
   }

NOTE: MFC's CString class exhibits this behavior.

Modification Type:	Minor	Last Reviewed:	7/5/2005
Keywords:	kbbug kbfix kbVS97sp1fix kbVS97sp2fix KB168010