[divakantpandey]

Fixes #2818

Problem

When indexing PlantUML sequence diagrams that contain messages to or from diagram edges (Alice ->: msg, Alice <-: msg, [-> Alice: msg, [<- Alice: msg), dg_puml_operand() receives an opener character without a matching closer.

dg_puml_operand() initialized *label = dg_s(NULL, 0); at its entry, but only wrote *id on success paths. On unmatched openers, if (!c) return i; returned early without writing *id. In callers dg_puml_relation() and dg_puml_decl(), lid, rid, id, and aid were uninitialized stack variables, causing if (!rid.n) to read stack garbage and pass unmapped addresses into dg_element() and dg_trim(), crashing the index worker with SIGSEGV.

Solution

• In dg_puml_operand(), initialize *id = dg_s(NULL, 0); at entry alongside *label.
• Zero-initialize lid, llab, rid, and rlab in dg_puml_relation(), and id, label, aid, and alab in dg_puml_decl().

Verification

• Added diagrams_plantuml_edge_messages_issue2818 in tests/test_diagrams.c.
• Verified failure toggle: reproduces deterministically under ASan+UBSan prior to fix (AddressSanitizer: global-buffer-overflow in dg_id_key from dg_element), passes cleanly after fix.
• ./scripts/test.sh --suites diagrams: 19/19 passed.
• ./scripts/test.sh --contracts-only: All static contract steps passed.
• ./scripts/check-dco.sh upstream/main..HEAD: Valid DCO sign-off verified.
• ./scripts/build.sh: Production binary builds cleanly.

[github-actions]

Thanks for opening this — it has been seen, and it is queued.

This note is automated, but it is not a brush-off: it exists so you know where your PR stands instead of having to guess from silence.

Current review status: working through a backlog. 0.9.1-rc.1 is out, so the release freeze that held reviews is over — but it left a large queue of open pull requests behind it, and we are reading through them oldest-first. The background is in discussion #1144.

What that means for this PR, concretely:

• It will not be closed for inactivity. No stale bot touches pull requests here.
• It may still sit a while before a human reads it. That is on us, not on you.
• Older PRs are read first, so a recent one is not being skipped — it is behind a queue.

Things that will genuinely speed it up whenever review does happen:

• Keep it rebased on main — the tree is moving quickly right now, and a conflicting branch cannot be reviewed as the diff you intended.
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• Keep the change to one claim. Bundled features and refactors get split before they get merged, which costs you a round trip.
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If this fixes a bug, a reproduction we can run is worth more than a description of the symptom.

Thanks for contributing, and sorry in advance for the wait.

[DeusData]

Thank you very much, @divakantpandey, for jumping on #2818 so quickly and for the clear write-up -- your diagnosis matches the root cause exactly, and your test reproduces the crash on main.

#2827 was opened a few hours earlier with the same one-line fix in dg_puml_operand, and it has now landed in 76dda7e with a test that also covers the unclosed-declaration path. Since both pull requests carry the same production change, we are closing this one as a duplicate rather than landing the fix twice; the extra zero-initializations in the callers are not needed once dg_puml_operand always writes both outputs.

This is no reflection on your work -- it was simply a race on a fresh issue. Thank you again; #2822 and #2833 are in the queue.