8288754: GCC 12 fails to build zReferenceProcessor.cpp

[shipilev]

When compiling with GCC 12.1.1 (current in Fedora rawhide), the following warning-as-error is produced and breaks the build by default:

/home/test/shipilev-jdk/src/hotspot/share/gc/z/zReferenceProcessor.cpp: In member function 'oopDesc* ZReferenceProcessor::drop(oop, ReferenceType)':
/home/test/shipilev-jdk/src/hotspot/share/gc/z/zReferenceProcessor.cpp:270:22: error: '%s' directive argument is null [-Werror=format-overflow=]
  270 | log_trace(gc, ref)("Dropped Reference: " PTR_FORMAT " (%s)", p2i(reference), reference_type_name(type));
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The problem is over-zealous compiler seeing NULL from ShouldNotReachHere() block, and complaining about it. In this particular case, we can dodge this by returning a more reasonable constant on failure path.

(This thing should be more reasonably handled when ShouldNotReachHere() is somehow nonreturn-ed, but Hotspot style doc is still undecided on this).

Additional testing:

• Linux x86_64 fastdebug build with GCC 12.1.1

---

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Issue

• JDK-8288754: GCC 12 fails to build zReferenceProcessor.cpp

Reviewers

• Kim Barrett (@kimbarrett - Reviewer) ⚠️ Review applies to 8312ecc1
• Albert Mingkun Yang (@albertnetymk - Reviewer) ⚠️ Review applies to 8312ecc1
• Stefan Karlsson (@stefank - Reviewer) ⚠️ Review applies to 8312ecc1
• Thomas Schatzl (@tschatzl - Reviewer)

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[openjdk]

@shipilev The following label will be automatically applied to this pull request:

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[mlbridge]

Webrevs

• 01: Full - Incremental (1b603dfd)
• 00: Full (8312ecc1)

[kimbarrett]

Looks good.

(This thing should be more reasonably handled when ShouldNotReachHere() is
somehow nonreturn-ed, but Hotspot style doc is still undecided on this).

The problem with using [[noreturn]] for assert/guarantee/ShouldNotReachHere
&etc is that they aren't currently noreturn, due to Debugging and
(in non-product builds) SuppressErrorAt. I've sometimes wondered if anyone
actually uses SuppressErrorAt. But I haven't pursued the question because of
Debugging, which seems to be involved in dealing with error handler
reentrancy or recursion or the like (I don't recall details).

[openjdk]

@shipilev This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8288754: GCC 12 fails to build zReferenceProcessor.cpp

Reviewed-by: kbarrett, ayang, stefank, tschatzl

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 4 new commits pushed to the master branch:

• e26d3b3: 8288497: add support for JavaThread::is_oop_safe()
• c74a923: 8288531: Empty spans in mobile navigation markup
• af05139: 8288467: remove memory_operand assert for spilled instructions
• b9c3966: 8288671: Problematic fix for font boosting

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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[stefank]

Looks good.

(This thing should be more reasonably handled when ShouldNotReachHere() is
somehow nonreturn-ed, but Hotspot style doc is still undecided on this).

The problem with using [[noreturn]] for assert/guarantee/ShouldNotReachHere &etc is that they aren't currently noreturn, due to Debugging and (in non-product builds) SuppressErrorAt. I've sometimes wondered if anyone actually uses SuppressErrorAt. But I haven't pursued the question because of Debugging, which seems to be involved in dealing with error handler reentrancy or recursion or the like (I don't recall details).

Also, see the discussion in https://bugs.openjdk.org/browse/JDK-8065585

[shipilev]

@stefank, do you agree with this patch?

[stefank]

Yes, that seems to be a good fix. I would have preferred to say "Unknown" instead of "ERROR", but that could be changed later if you want to push.

[shipilev]

Oh, we can change that to Unknown, no problem there.

[shipilev]

/integrate

[openjdk]

Going to push as commit 834d92d.
Since your change was applied there have been 8 commits pushed to the master branch:

• 198cec9: 8286103: VThreadMonitorTest fails "assert(!current->cont_fastpath() || (current->cont_fastpath_thread_state() && !interpreted_native_or_deoptimized_on_stack(current))) failed"
• 97200a7: 8278053: serviceability/jvmti/vthread/ContStackDepthTest/ContStackDepthTest.java failing in loom repo with Xcomp
• 31d981e: 8288532: additional review changes for JDK-8286830
• a144988: 8288139: JavaThread touches oop after GC barrier is detached
• e26d3b3: 8288497: add support for JavaThread::is_oop_safe()
• c74a923: 8288531: Empty spans in mobile navigation markup
• af05139: 8288467: remove memory_operand assert for spilled instructions
• b9c3966: 8288671: Problematic fix for font boosting

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 834d92d.

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