[cfe-dev] Using isa & co with custom class hierarchy

[Victor Zverovich]

Hi Jan,

I think 'classof' should be virtual for isa<> and friends to work. In
addition you can provide a static 'classof' for the same class that will
speed up the cases like isa<A>(a) and isa<A>(b).

Regards,
Victor

On Wed, Aug 25, 2010 at 4:02 PM, Jan Bierbaum <s3306700 at inf.tu-dresden.de>wrote:

> Hi!
>
> I hope I'm not too OT with that question, but Clang makes extensive use
> of this mechanism so maybe somebody can help me.
>
> LLVM provides isa<>, cast<> and so on. Recently I tried to make use of
> this for my own class hierarchy, but failed.
>
> >From the documentation and examples in Clang's code I figured that the
> only thing to do was add a static method 'classof' to any involved class
> with a parameter that will match any parent class. Then inside this
> method do any checks necessary and return 'true' if the current instance
> is indeed of the type given.
>
> But when I do this I get 'true' for any 'isa<>' I try!?
>
> Attached is a small example that outputs the following:
>
> | $ ./a.out
> | isa<A>(a) = 1
> | isa<B>(a) = 1
> | isa<B>(b) = 1
> | isa<A>(b) = 1
>
> What I would expect instead is the second line to yield false/0, since a
> is an instance of class A which "is" no B.
>
> Can somebody please give me a hint on what I'm doing wrong?
>
>
> Regards, Jan.
>
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