8367766: [11u] src/jdk.crypto.ec/share/native/libsunec/impl/mpi.c:321:3: error: 'tmp.dp' may be used uninitialized

[zzambers]

This error/warning has been seen on newer gcc versions on openjdk 11:

In function 'mp_zero',
    inlined from 'mp_zero' at /home/tester/temurinbuild-1757944128/workspace/build/src/src/jdk.crypto.ec/share/native/libsunec/impl/mpi.c:316:8,
    inlined from 'mp_set_int' at /home/tester/temurinbuild-1757944128/workspace/build/src/src/jdk.crypto.ec/share/native/libsunec/impl/mpi.c:353:3,
    inlined from 'mp_cmp_int' at /home/tester/temurinbuild-1757944128/workspace/build/src/src/jdk.crypto.ec/share/native/libsunec/impl/mpi.c:1735:26:
/home/tester/temurinbuild-1757944128/workspace/build/src/src/jdk.crypto.ec/share/native/libsunec/impl/mpi.c:321:3: error: 'tmp.dp' may be used uninitialized [-Werror=maybe-uninitialized]
  321 |   s_mp_setz(DIGITS(mp), ALLOC(mp));
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/tester/temurinbuild-1757944128/workspace/build/src/src/jdk.crypto.ec/share/native/libsunec/impl/mpi.c: In function 'mp_cmp_int':
/home/tester/temurinbuild-1757944128/workspace/build/src/src/jdk.crypto.ec/share/native/libsunec/impl/mpi.c:1730:11: note: 'tmp' declared here
 1730 |   mp_int  tmp;
      |           ^~~

Problem does not affect newer jdks, because affected code was removed by JDK-8235710.

Also whether warning/error is generated depends on other conditions like compiler version / arch / build kind etc. Seems like compiler needs to do enough inlining to detect this, as analysis needs to cross function boundary.

Details/Fix:
Underlining issue seems to be that mp_init called on tmp (struct) may theoretically fail, unitialized tmp would then still be passed to subsequent functions. Unfortunately mp_cmp_int is not really designed to be able to handle errors.

So I just zero initialize tmp, which makes error/warning go away. I think making more involved changes to API/implementation is probably not worth the effort, especially when code is for legacy curves, removed in newer jdks. It would also increase risk of regressions.

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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• Commit message must refer to an issue
• JDK-8367766 needs maintainer approval

Issue

• JDK-8367766: [11u] src/jdk.crypto.ec/share/native/libsunec/impl/mpi.c:321:3: error: 'tmp.dp' may be used uninitialized (Bug - P4 - Requested)

Reviewers

• Paul Hohensee (@phohensee - Reviewer)
• Severin Gehwolf (@jerboaa - Reviewer)

Reviewing

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[bridgekeeper]

👋 Welcome back zzambers! 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]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[mlbridge]

Webrevs

• 01: Full - Incremental (3807d756)
• 00: Full (095d6b69)

[bridgekeeper]

@zzambers This pull request has been inactive for more than 4 weeks and will be automatically closed if another 4 weeks passes without any activity. To avoid this, simply issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

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@zzambers This pull request has been inactive for more than 8 weeks and will now be automatically closed. If you would like to continue working on this pull request in the future, feel free to reopen it! This can be done using the /open pull request command.

[zzambers]

/open

[openjdk]

@zzambers This pull request is now open

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@zzambers This pull request has been inactive for more than 4 weeks and will be automatically closed if another 4 weeks passes without any activity. To avoid this, simply issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

[zzambers]

/touch

[openjdk]

@zzambers The pull request is being re-evaluated and the inactivity timeout has been reset.

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@zzambers This pull request has been inactive for more than 4 weeks and will be automatically closed if another 4 weeks passes without any activity. To avoid this, simply issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

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@zzambers This pull request has been inactive for more than 8 weeks and will now be automatically closed. If you would like to continue working on this pull request in the future, feel free to reopen it! This can be done using the /open pull request command.

[zzambers]

/open

[openjdk]

@zzambers This pull request is now open

[phohensee]

Reasonable.

[openjdk]

⚠️ @zzambers This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

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@zzambers This pull request has been inactive for more than 4 weeks and will be automatically closed if another 4 weeks passes without any activity. To avoid this, simply issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

[jerboaa]

@zzambers Could you please merge latest master to get updated CI runs? Thank you!

[zzambers]

/template append

[openjdk]

@zzambers The pull request template has been appended to the pull request body

[jerboaa]

LGTM

[zzambers]

/approval request trivial change to avoid compiler warning/error, low risk, tests OK

[openjdk]

@zzambers
8367766: The approval request has been created successfully.