Commits on Oct 15, 2024

1. [libc++] Avoid re-exporting a few specific symbols from libc++abi (ll… …

   …vm#109054)
   
   In 6a884a9, I synchronized the export list of libc++abi to the
   export list of libc++. From the linker's perspective, this caused these
   symbols to be taken from libc++.dylib instead of libc++abi.dylib.
   
   However, that can be problematic when back-deploying. Indeed, this means
   that the linker will encode an undefined reference to be fullfilled by
   libc++.dylib, but when backdeploying against an older system, that
   symbol might only be available in libc++abi.dylib.
   
   Most of the symbols that started being re-exported after 6a884a9
   turn out to be implementation details of libc++abi, so nobody really
   depends on them and this back-deployment issue is inconsequential.
   
   However, we ran into issues with a few of these symbols while testing
   LLVM 19, which led to this patch. This slipped between the cracks and
   that is why the patch is coming so long after the original patch landed.
   
   In the future, a follow-up cleanup would be to stop exporting most of
   the _cxxabiv1_foo_type_infoE symbols from both libc++abi and libc++
   since they are implementation details that nobody should be relying on.
   
   rdar://131984512
   (cherry picked from commit 677e8cd)

   

   ldionne authored and tru committed Oct 15, 2024
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