[Webkit-unassigned] [Bug 67851] WTFString.h should include template specialization for HashTraits<String>

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=67851





--- Comment #5 from Sam Weinig <sam at webkit.org>  2011-09-12 09:55:31 PST ---
(In reply to comment #4)
> This code doesn't compile and I think it should:
> 
>   #include <wtf/HashSet.h>
>   #include <wtf/text/WTFString.h>
> 
>   class ScoobyDoo {
>     HashSet<String> scrappy;
>   };
> 
>   #include <wtf/text/StringHash.h>
> 
> Here's the error I get:
> 
>   wtf/text/StringHash.h: At global scope:
>   wtf/text/StringHash.h:182: error: specialization of ‘WTF::HashTraits<WTF::String>’ after instantiation
>   wtf/text/StringHash.h:182: error: redefinition of ‘struct WTF::HashTraits<WTF::String>’
>   wtf/HashTraits.h:57: error: previous definition of ‘struct WTF::HashTraits<WTF::String>’
>   In file included from wtf/text/StringImpl.h:33,
>                    from wtf/text/WTFString.h:28,
> 
> This can occur if one header file includes HashSet.h and String.h and declares a HashSet<String> (perfectly reasonable on its own) and then a later header file includes StringHash.h. I hit this in a unit test I'm working on, so it's not theoretical.

I don't think it is perfectly reasonable.  I believe you are supposed to #include <wtf/text/StringHash.h> if you want to use a HashSet<String>.  Perhaps we should make it easier to ensure you are doing this right, but I am not sure #including <wtf/HashTraits.h> everywhere we #include <wtf/text/WTFString.h> is the right way to go (it might be though.)

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