[PATCH] D46665: [Itanium] Emit type info names with external linkage.

[John McCall via Phabricator via cfe-commits]

rjmccall added a comment.

In https://reviews.llvm.org/D46665#1102348, @rsmith wrote:

> In https://reviews.llvm.org/D46665#1102290, @rjmccall wrote:
>
> > I believe static and dynamic linkers — at least on ELF and Mach-O — will always drop weak symbols for strong ones.  Now, I think that isn't LLVM's posted semantics for linkonce_odr, but to me that means that LLVM's semantics are inadequate, not that we should decline to take advantage of them.
> >
> > If we can't rely on that, it probably means that the type name symbol for class types always has to be linkonce_odr, even if it's for a type with a key function.
>
>
> That all makes sense to me. (But I think `weak_odr` would be more formally correct, even though the symbol will never actually be discarded as it's referenced from the type_info and vtable.)


Yes, of course.

> The rule that ASan is using is that if there is an `external` definition for a global variable, there should not be any other definitions for that symbol, which seems right given LLVM's semantics, but wrong here.

I agree.

> For now, the simplest thing to do seem to be to weaken `external` linkage to `weak_odr` for the type info name.

Yes.


Repository:
  rC Clang

https://reviews.llvm.org/D46665