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

[Adrian McCarthy via llvm-dev]

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

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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