8283059: Uninitialized warning in check_code.c with GCC 11.2

[vidmik]

Note: this PR replaces the one I messed up earlier.

Background, from JBS:

src/java.base/share/native/libverify/check_code.c: In function 'read_all_code':
src/java.base/share/native/libverify/check_code.c:942:5: error: 'lengths' may be used uninitialized [-Werror=maybe-uninitialized]
942 | check_and_push(context, lengths, VM_MALLOC_BLK);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/java.base/share/native/libverify/check_code.c:4145:13: note: by argument 2 of type 'const void *' to 'check_and_push' declared here
4145 | static void check_and_push(context_type *context, const void *ptr, int kind)
| ^~~~~~~~~~~~~~

Because the second argument of check_and_push is "const void*" GCC assumes that the malloc:ed data, which has not yet been initialized, will not be/can not be modified later which in turn suggests it may be used without ever being initialized.

The same general issue was addressed in JDK-8266168, presumably for GCC 11.1.

Details:

Instead of sprinkling more calloc calls around or using pragmas/gcc attributes I chose to change the check_and_push function to take a (non-const) void* argument, and provide a new wrapper function check_and_push_const which handles the const argument case. For the (non-const) VM_MALLOC_BKP that means the pointer never needs to go through a const conversion.

To avoid having multiple ways of solving the same problem I also chose to revert the change made in JDK-8266168, reverting the calloc back to a malloc call.

Testing:

tier1 + builds-tier{2,3,4,5}

---

Progress

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• Commit message must refer to an issue
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Issue

• JDK-8283059: Uninitialized warning in check_code.c with GCC 11.2

Reviewers

• David Holmes (@dholmes-ora - Reviewer)

Reviewing

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[bridgekeeper]

👋 Welcome back mikael! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

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

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[mlbridge]

Webrevs

• 01: Full - Incremental (9f412d0b)
• 00: Full (c5c60cb2)

[vidmik]

/label add hotspot-runtime

[openjdk]

@vidmik
The hotspot-runtime label was successfully added.

[vidmik]

Added hotspot-runtime to the new version of the PR.

[dholmes-ora]

Looks good!

[openjdk]

@vidmik 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:

8283059: Uninitialized warning in check_code.c with GCC 11.2

Reviewed-by: dholmes

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At the time when this comment was updated there had been 1 new commit pushed to the master branch:

• 002e366: 8283325: US_ASCII decoder relies on String.decodeASCII being exhaustive

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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[vidmik]

/integrate

[openjdk]

Going to push as commit d8893fa.
Since your change was applied there have been 9 commits pushed to the master branch:

• ff0b092: 8278794: Infinite loop in DeflaterOutputStream.finish()
• b2aa085: 8283378: JFR: Checkpoint classes not renamed properly
• 85cc6f1: 8283315: jrt-fs.jar not always deterministically built
• c72bcfc: 8283289: JFR: Rename CheckPoint
• 4b5079b: 8283202: Potential off-read when checking JFR's status in awaitFinished
• b96cb04: 8283353: compiler/c2/cr6865031/Test.java and compiler/runtime/Test6826736.java fails on x86_32
• cab4ff6: 8283225: ClassLoader.c produces incorrect OutOfMemory Exception when length is 0 (aix)
• d83cee9: 8282407: Missing ')' in MacResources.properties
• 002e366: 8283325: US_ASCII decoder relies on String.decodeASCII being exhaustive

Your commit was automatically rebased without conflicts.

[openjdk]

@vidmik Pushed as commit d8893fa.

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