Investigate why CI or check-cxx with ubsan does not detect the issue

[vitalybuka]

#152181 should fix the issue. I'd really like to know why this wasn't caught in the CI though. Is there some special flag required to check for this kind of stuff?

I believe CI has check-cxx with ubsan, our bot has "check-cxx with ubsan" and it does not fail.

What fails is using libcxx to compile llvm. Type from report is:

std::map<std::string, std::unique_ptr<ACLEIntrinsic>> ACLEIntrinsics;

So I guess libcxx lack of test coverage for them?

Originally posted by @vitalybuka in #152180 (comment)

After #151304 sanitizer-x86_64-linux-bootstrap-ubsan fails to compile LLVM,
but no other CI is broken.

[vitalybuka]

@alazarev @philnik777 Assigning to my self, but feel free to look into that if you have time.

[llvmbot]

@llvm/issue-subscribers-infrastructure

Author: Vitaly Buka (vitalybuka)

> #152181 should fix the issue. I'd really like to know why this wasn't caught in the CI though. Is there some special flag required to check for this kind of stuff?

I believe CI has check-cxx with ubsan, our bot has "check-cxx with ubsan" and it does not fail.

What fails is using libcxx to compile llvm. Type from report is:

std::map<std::string, std::unique_ptr<ACLEIntrinsic>> ACLEIntrinsics;

So I guess libcxx lack of test coverage for them?

Originally posted by @vitalybuka in #152180 (comment)

After #151304 sanitizer-x86_64-linux-bootstrap-ubsan fails to compile LLVM,
but no other CI is broken.

[vitalybuka]

So check-cxx covers similar set/map use-cases, and I fails to create test case which trigger ubsan.

check-cxx on the bot sanitizer-x86_64-linux-bootstrap-ubsan does not trigger, I assume for the same reasons libcxx CI as well.

I tried to copy command line from llvm table-gen compilation, and use for standalone executable, it still does not trigger.

[vitalybuka]

From discord by @philnik777:

I've figured out why we don't get any errors in our CI: clang++: warning: the object size sanitizer has no effect at -O0, but is explicitly enabled: -fsanitize=object-size [-Winvalid-command-line-argument]. I wonder whether we should just enable UBSan in our optimized build...