Re: [boost] [variant] static_visitor has no virtual destructor.

Subject: Re: [boost] [variant] static_visitor has no virtual destructor.
From: Krzysztof Czainski (1czajnik_at_[hidden])
Date: 2012-11-07 13:40:51

2012/11/7 Pierre Talbot <ptalbot_at_[hidden]>

> Hello,
>
> I have a compilation error with Boost (1.52) and g++ (4.7) with the flag
> -Weffc++:
>
> error: base class ‘class boost::static_visitor<std::**basic_string<char>
> >’ has a non-virtual destructor [-Werror=effc++]
>
> And the static_visitor class is defined with a protected non-virtual
> destructor:
>
> template <typename R = ::boost::detail::static_**visitor_default_return>
> class static_visitor
>     : public detail::is_static_visitor_tag
> {
> public: // typedefs
>
>     typedef R result_type;
>
> protected: // for use as base class only
>
>     static_visitor() { }
>     ~static_visitor() { }
>
> };
>
> Is it normal ? And if it is, how to avoid this error ?
>
> Thank you for your help,
>
> Pierre Talbot.
>

I think your compiler is wrong about this. Please see "Guideline #4: A base
class destructor should be either public and virtual, or protected and
nonvirtual." [1]  ;-)

HTH, Kris

[1] http://www.gotw.ca/publications/mill18.htm