[Webkit-unassigned] [Bug 113454] GCC 4.8 error - C++ nested class inheriting enclosing class

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=113454


Benjamin Poulain <benjamin at webkit.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #195676|review?                     |review+
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--- Comment #12 from Benjamin Poulain <benjamin at webkit.org>  2013-03-28 20:27:54 PST ---
(From update of attachment 195676)
View in context: https://bugs.webkit.org/attachment.cgi?id=195676&action=review

> Source/WTF/ChangeLog:38
> +        Original code has nested classes that have enclosing class as their parent, illustrated below -
> +          template class <typename T>
> +          class HashMap {
> +            ... ...
> +            ... ...
> +          private:
> +            class HashMapKeysProxy;
> +
> +            // ERROR - nested class inherits enclosing class.
> +            class HashMapKeysProxy : private HashMap {
> +            };
> +            ... ...
> +            ... ...
> +          };
> +
> +        Fixed as below:
> +          template class <typename T>
> +          class HashMap {
> +            ... ...
> +            ... ...
> +          private:
> +            class HashMapKeysProxy;
> +
> +            ... ...
> +            ... ...
> +          };
> +
> +          template <typename T>
> +          class HashMap<T>::HashMapKeysProxy : private HashMap<T> {
> +            ... ...
> +          };

The patch is great but I am still not happy about the ChangeLog.

What you need is explain what, why and how.

Basically explain: the previous code does not build on GCC 4.8. The reason is HashMapKeysProxy and HashMapValuesProxy are defined as nested class inside HashMap, which is illegal (you can like to a spec if possible). The solution here is to move the said definitions outside of HashMap.

> Source/WTF/wtf/HashMap.h:264
> -        m_impl.swap(other.m_impl); 
> +        m_impl.swap(other.m_impl);
>      }
>  
>      template<typename T, typename U, typename V, typename W, typename X>
>      inline int HashMap<T, U, V, W, X>::size() const
>      {
> -        return m_impl.size(); 
> +        return m_impl.size();
>      }
>  
>      template<typename T, typename U, typename V, typename W, typename X>
>      inline int HashMap<T, U, V, W, X>::capacity() const
> -    { 
> -        return m_impl.capacity(); 
> +    {
> +        return m_impl.capacity();
>      }

Better leave those unchanged, it is unrelated with your fix.

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