[PATCH] D141472: [clang][Interp] Add function pointers

[Timm Bäder via Phabricator via cfe-commits]

tbaeder added a comment.

> Member pointers (for functions or for data) are weird in that they're not the typical pointer width. They're actually a pointer and between one-to-three other fields in a trenchcoat, depending on the circumstances. You generally need the function pointer, but you also may need various offsets (to this, to the vtable, etc). There's some more information about how it's done in MSVC (which is different from Itanium ABI, but we can do what we want for the constant expression interpreter): https://rants.vastheman.com/2021/09/21/msvc/
>
> I don't think there's a problem with `FunctionPointer` per se, I'm more wondering are you planning to also add a `MemberPointer` type or are you planning to reuse `FunctionPointer` to handle function members (and presumably something else for data members)?
>
> As for virtual functions in general, the standard has rules: http://eel.is/c++draft/expr.const#5.6 and http://eel.is/c++draft/expr.const#7

I was thinking that the `dynamicDispatch` in https://godbolt.org/z/rf9Ks77Wo would be a good reproducer since the actual function to call is only known when calling `dynamicDispatch()`, but that example already works when doing a few changes to `classify()` the right types and adding a `if (BO->isPtrMemOP()) { return visit(RHS); }` to `VisitBinaryOperator()`.


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  https://reviews.llvm.org/D141472/new/

https://reviews.llvm.org/D141472