[compiler-rt] [libcxxabi] [libunwind] [runtimes][PAC] Harden unwinding when possible (#138571) (PR #143230)

[Anatoly Trosinenko via llvm-commits]

https://github.com/atrosinenko commented:

@ojhunt Thank you for the update! I like the idea of not checking for `__has_include(<ptrauth.h>)` separately, as it was done in your latest version of `gcc_personality_v0.c`. I wonder if other instances of `#if __has_include(<ptrauth.h>)` are worth replacing with unconditionally including `ptrauth.h` as soon as it is decided to use its features according to `__has_feature(...)` tests (and erroring out in case this file is absent). Are there any expected use cases when absence of `ptrauth.h` has to be handled gracefully?

https://github.com/llvm/llvm-project/pull/143230