PATCH: don't mark pure derived method odr because of a qualified call to base method

[Nick Lewycky]

Thinking about this issue more, I'd like to retract this patch. Consider
the case where we're implementing the rule that all ODR-used inline
functions must have a definition. If Derived::fn is marked inline, we'll
see a fictitious use of it and reject a valid translation unit.

My next plan is to remove this code from Sema entirely and do the
equivalent work inside codegen proper. No reason it can't keep track of
probable virtual function targets when writing out a virtual dispatch.

Nick


On 12 February 2013 19:30, Nick Lewycky <nlewycky at google.com> wrote:

> I failed to produce a concise explanation of the patch, so I'll lead off
> with the testcase:
>
>   struct Base { virtual void fn() { } };
>   struct Derived : public Base { virtual void fn() = 0;
>     void test() { Base::fn(); /* triggers an ODR-use of Derived::fn() */ }
>   };
>
> This is because we repurpose the odr bit on virtual functions to mean "it
> would be convenient for codegen to emit this", to help devirtualization for
> instance. This is implemented in Sema with a scan through all known derived
> classes when building a member expression, in this case "this->Base::fn".
> This patch makes that scan skip pure methods.
>
> Patch attached, please review.
>
> Nick
>
>
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