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From: Bo Persson (bop_at_[hidden])
Date: 2007-05-05 06:17:51

Jonathan Franklin wrote:
:: On 5/4/07, David Abrahams <dave_at_[hidden]> 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

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