[libcxx-commits] [PATCH] D114385: [libunwind] Fix testing with sanitizers enabled

[Leonard Chan via Phabricator via libcxx-commits]

leonardchan added a comment.

> The unwind_leaffunction.pass.cpp test was failing with ubsan because it was
> relying on undefined behavior to "do the right thing" and result in a SIGSEGV.
> IMO it makes more sense to simply raise a SIGSEGV directly, since that is guaranteed
> to work.

It looks like using `raise` causes this test to fail on our aarch64 builder <https://luci-milo.appspot.com/ui/p/fuchsia/builders/toolchain.ci/clang-linux-arm64/b8829557385974689473/overview> with exit code 255 (from the `_Exit(-1)` in `signal_handler`). I'm unsure why it would fail when using `raise`. These are a couple of things I noticed when debugging:

- If I replace `raise(SIGSEGV)` with `kill(getpid(), SIGSEGV)`, the test passes normally. The man page <https://man7.org/linux/man-pages/man3/raise.3.html> for raise says this is functionally equivalent.
- If I manually print out the frame names from `info.dli_sname`, I notice with `raise` I only cover 2 frames (`_Z14signal_handleri`, `__kernel_rt_sigreturn`) but with `kill` I get 5 frames (`_Z14signal_handleri`, `__kernel_rt_sigreturn`, `kill`, `_Z18crashing_leaf_funcv`, `main`).
  - If I use the old UB approach, I get 4 frames (just excluding the call to `kill`).

Any ideas for why this might be the case?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D114385/new/

https://reviews.llvm.org/D114385