Pure virtual destructor in C++

c++ polymorphism destructor pure-virtual
Ivan Krechetov picture Ivan Krechetov · Mar 10, 2009 · Viewed 78.7k times · Source

Is it wrong to write:

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

for an abstract base class?

At least that compiles in MSVC... Will it crash at run time?

Answer

MSN picture MSN · Mar 10, 2009

Yes. You also need to implement the destructor:

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

inline A::~A() { }

should suffice.

And since this got a down vote, I should clarify: If you derive anything from A and then try to delete or destroy it, A's destructor will eventually be called. Since it is pure and doesn't have an implementation, undefined behavior will ensue. On one popular platform, that will invoke the purecall handler and crash.

Edit: fixing the declaration to be more conformant, compiled with http://www.comeaucomputing.com/tryitout/

Related questions

When to use virtual destructors?

I have a solid understanding of most OOP theory but the one thing that confuses me a lot is virtual destructors. I thought that the destructor always gets called no matter what and for every object in the chain. When …

Read More
Where do "pure virtual function call" crashes come from?

I sometimes notice programs that crash on my computer with the error: "pure virtual function call". How do these programs even compile when an object cannot be created of an abstract class?

Read More
Private virtual method in C++

What is the advantage of making a private method virtual in C++? I have noticed this in an open source C++ project: class HTMLDocument : public Document, public CachedResourceClient { private: virtual bool childAllowed(Node*); virtual PassRefPtr<Element> createElement(const …

Read More