RFR: JDK-8298445: Add LeakSanitizer support in HotSpot [v6]

[Magnus Ihse Bursie]

On Tue, 7 Feb 2023 15:40:34 GMT, Justin King <jcking at openjdk.org> wrote:

>> Adds initial LSan (LeakSanitizer) support to Hotspot. This setup has been used to identify multiple leaks so far. It can run most of the test suite except those that also fail with ASan, which is being looked at separately. It is especially useful when combined with ASan, as LSan can use poisoning information to determine what memory to scan or not to scan, making leak detection more accurate and faster.
>> 
>> **Suppressing:**
>> Currently the suppression list is only used to suppress JLI leaks that are known, the rest are done in code. Suppressing needs to identify the source of thet leak. Due to Hotspot's code organization, we would need to suppress `os::malloc` and friends, which would suppress everything. Suppressing in code has the added benefit of being explicit and surviving refactors if methods change.
>> 
>> **Caveats:**
>> - By default ASan enables LSan, however we explicitly disable it unless `--enable-lsan` is given. It is useful to be able to use ASan without LSan. Using LSan by itself is less likely to be useful and will probably not work, but its still possible currently.
>
> Justin King has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Revert changes to JDK
>   
>   Signed-off-by: Justin King <jcking at google.com>

I apologize, the fault lies entirely with me. Justin should have no blame in this -- he is not a committer and is not expected to fully know all rules for integration. That responsibility lies with the sponsor, in this case, me.

I read @dholmes-ora's comment:
> Updates look good - glad to see the flag changes go away!

> I suggest factoring out the change to test/jdk/jni/nullCaller/exeNullCallerTest.cpp as it is a JDK test and not part of hotspot. Thanks.

as an approval from Hotspot, given that the JDK test was removed, which a later commit did indeed remove. And, like Justin, I interpreted Thomas comments as questions that were now answered, rather than an ongoing discussion about the 

I did not realize there were still an ongoing discussion, and was too eager to sponsor this PR.

@tstuefe @dholmes-ora Do you want me to revert this change? Or should we continue the discussion in a follow-up bug that can address the remaining problems?

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PR: https://git.openjdk.org/jdk/pull/12229