When Should a C Destructor Be Pure Virtual?

Why Do We Need a Pure Virtual Destructor in C ?

Virtual destructors are essential in C to ensure proper cleanup of objects when dealing with inheritance and polymorphism. However, why do we need specifically pure virtual destructors?

When to Use a Pure Virtual Destructor

Pure virtual destructors are primarily used when we want to declare a class as abstract. This means classes derived from an abstract class must override the destructor.

However, it is worth noting that making a destructor pure virtual does not automatically make the class abstract. One can make a class abstract by making any of its member functions pure virtual.

Is It a Good Practice to Make the Destructor Pure Virtual in Abstract Classes?

No, it is generally not considered good practice to make the destructor pure virtual in abstract classes. A plain virtual destructor suffices to declare the class as abstract.

The reason is that the compiler will automatically generate an implicit destructor for derived classes if the class's author does not define one. This implicit destructor will not be pure virtual, which means the derived classes will not be abstract solely because of the pure virtual destructor in the base class.

Additional Benefits

While not strictly necessary for the purpose of making a class abstract, pure virtual destructors can sometimes be convenient as a reminder to derived classes that specific cleanup code is required. However, this approach is considered somewhat contrived and unenforced.

Conclusion

In C , pure virtual destructors are not essential for declaring a class as abstract, as any pure virtual member function can fulfill this purpose. Their primary benefit is providing a reminder to derived classes that specific cleanup code is required.

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