Why does enable_shared_from_this have a non-virtual destructor?

Question

I have a pet project with which I experiment with new features of C++11. While I have experience with C, I\'m fairly new to C++. To train myself into best practices, (besides re

Answer 1

A destructor of a class that is intended for subclassing should always be virtual, IMHO.

A virtual destructor in a base class is only needed if an instance of the derived class is going to be deleted via a pointer to the base class.

Having any virtual function in a class, including a destructor, requires overhead. Boost (and the TR1 and C++11 Standard Library) doesn't want to force you to have that overhead just because you need to be able to obtain a shared_ptr from the this pointer.

The destructor is empty, why have it at all?

If you don't have a user-defined constructor, the compiler provides one for you, so it doesn't really matter.

I can't imagine anyone would want to delete their instance by reference to enable_shared_from_this.

Exactly.

As for the compiler warning, I would ignore the warning or suppress it (with a comment in the code explaining why you are doing so). Occasionally, especially at "pedantic" warning levels, compiler warnings are unhelpful, and I'd say this is one of those cases.