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Pure Virtual Destructors

Pure Virtual Destructors

Question:
I heard someone saying that C++ standardization does not allow pure virtual destructors not to have a definition.

As far as I know, this is not true. Could you please confirm? I cannot find the relevant information.

Answer:
It is true: a pure virtual destructor must be defined. The reason is that a derived object’s destructor recursively calls its base class’s destructor. When the base’s destructor is only declared but not implemented (as is the case of a nonimplemented pure virtual destructor), the compiler issues an error message, and rightfully so. The implementation of a pure virtual destructor is located outside the class declaration, and it must be empty:

 class A{public: virtual ~A()=0; //declaration};virtual A::~A(){} //implementation

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