Jonathan Franklin wrote: :: On 5/4/07, David Abrahams <dave@boost-consulting.com> wrote: ::: ::: ::: For example, GCC has a ::: warning about a derived class whose base doesn't have a virtual ::: dtor. It's actually *impossible* (not just inefficient or ::: convoluted) to implement is_polymorphic without generating that ::: warning. :: :: :: Interesting. I'm obviously flaunting my ignorance, but I didn't :: realize :: that inheriting from a class sans virtual dtor was ever a Good :: Thing. I'll have to read up on the issues WRT is_polymorphic. :: Here's an example from the standard library: template<class _Ty> struct plus : public binary_function<_Ty, _Ty, _Ty> { // functor for operator+ _Ty operator()(const _Ty& _Left, const _Ty& _Right) const { // apply operator+ to operands return (_Left + _Right); } }; Neither plus nor binary_function has any virtual destructor, but they are still useful. You will not use them polymorphically though. Bo Persson