[llvm-dev] How to debug a test that fails only on some build bots?

[Adrian Prantl via llvm-dev]

Here are a couple of strategies that helped me in the past:

- Try to copy the cmake invocation from the bot's logs and reproduce it locally.

  --> Particularly the bots you list I think all don't build an X86 backend, so maybe that's it.

- Ask for help from the maintainer of the bot
- [last resort] Commit a change that duplicates the failing command without piping it through FileCheck, so you can see the output in the bot's log.

-- adrian

> On Jan 4, 2018, at 4:51 PM, Adrian McCarthy via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> I tried to land a small fix before going on vacation at the end of the year, but I had to revert it because it broke on a few of the build bots, specifically clang-cmake-thumbv7-a15, clang-cmake-armv7-a15, and llvm-hexagon-elf.
> 
> https://reviews.llvm.org/D41264 <https://reviews.llvm.org/D41264>
> 
> It seemed to work as expected on the others.
> 
> Unfortunately, the build logs don't give many clues.  The fix included a new test, and that test failed with an exit code of 1 but with no messages.  For example:
> FAIL: LLVM :: DebugInfo/void-typedef.ll (14416 of 23113)
> ******************** TEST 'LLVM :: DebugInfo/void-typedef.ll' FAILED ********************
> Script:
> --
> /local/buildbot/slaves/hexagon-build-02/llvm-hexagon-elf/llvm.obj/bin/llc /local/buildbot/slaves/hexagon-build-02/llvm-hexagon-elf/llvm.src/test/DebugInfo/void-typedef.ll -o - 2>&1 | /local/buildbot/slaves/hexagon-build-02/llvm-hexagon-elf/llvm.obj/bin/FileCheck /local/buildbot/slaves/hexagon-build-02/llvm-hexagon-elf/llvm.src/test/DebugInfo/void-typedef.ll
> --
> Exit Code: 1
> 
> 
> ********************
> I would have expected FileCheck messages telling me how the output differed from expectations.  Since I don't see any of that, I'm assuming there was a problem with the command itself, but I'm not sure why that would happen on just a few buildbots.
> 
> I haven't been able to reproduce the failures locally on Linux or Windows, so I'm not sure how to go about debugging this.  Any tips?
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