Re: [boost] [1.34.0beta] many, many warnings... :(

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