tbaeder added a comment. In D141472#4107008 <https://reviews.llvm.org/D141472#4107008>, @aaron.ballman wrote:
> In D141472#4106091 <https://reviews.llvm.org/D141472#4106091>, @tbaeder wrote: > >>> 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()`. > > That is a reasonable test, but probably not sufficient as nothing is really > testing the layout of those objects (the calls return a constant). How about > a test like: https://godbolt.org/z/rhhhvxYxf where there are offsets to > member variables involved? Ah I get what you mean now. The pointer we have on the stack is of type `S` but then we end up calling a function expecting a `S2` pointer, and which one we're calling is not known at compile time. I'm not sure what to do about this right now. I was wondering about restructuring pointers so all the metadata is before all the actual data, but that would be a large refactoring. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D141472/new/ https://reviews.llvm.org/D141472 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
