[PATCH] D47233: [CodeGen] Emit MSVC RTTI for Obj-C EH types

[David Chisnall via Phabricator via cfe-commits]

theraven added a comment.

In https://reviews.llvm.org/D47233#1129810, @DHowett-MSFT wrote:

> We ran into some critical issues with this approach on x64. The pointers in the exception record are supposed to be image-relative instead of absolute, so I tried to make them absolute to libobjc2's load address, but I never quite solved it.
>
> A slightly better-documented and cleaner version of the code you linked is here <https://github.com/Microsoft/libobjc2/blob/upstream-staging/eh_win32_msvc.cc>.


(For the reference of other people, since Dustin and I discussed this offline a while back)

This is fixed upstream.  We use a stack address as our base address and construct stack-variable-relative offsets.  This is safe to do because the only requirement for Win64 EH is that the pointers be relative to some arbitrary base and in the SEH model the throwing stack frame remains live until the last catch.


Repository:
  rC Clang

https://reviews.llvm.org/D47233