myxce/.wolf/bugs/bug-1504.md
Rongsong Shen d26ff8870d
feat(buglog): one Markdown record per bug, checked against a record standard
The buglog was one 27K-line JSON file whose fields covered only symptom,
root cause and fix, as free text: 2% of entries named the code version a
bug was found on, 12% the build profile, 36% a way to reproduce, and 58% of
the file was OpenWolf hook auto-detections ("Missing guard clause",
"Function not marked async" on .md files).

- .claude/skills/buglog/bug-record.md: the record standard. Eight
  sections (Summary as the title, Description, Environment, Reproduction;
  Root cause, Fix, Verification, References once fixed), each with the
  content it must contain -- e.g. Environment needs the OS, the libc the
  failing binary loads (from its ELF interpreter: glibc 2.42 in the nix
  shell vs 2.40 on the host), toolchain, build profile and commit.
- .wolf/bugs/<id>.md: 500 records migrated from buglog.json; every field
  verified to round-trip. They carry legacy: true and an explicit "not
  recorded" where the old log had no such field; component derived from
  file paths, severity from keywords (else unknown), fix_commits from
  hashes in status_note/fix that git resolves (91 of 463 fixed).
- .wolf/buglog-archive.json: the 710 hook auto-detections, verbatim.
- .wolf/buglog.json is now an index generated from the records, keeping
  the fields OpenWolf's hooks and `openwolf bug search` read.
- scripts/buglog.py rewritten: new (template + Environment collected from
  the machine and --binary), check, status (refuses a status the record
  doesn't support; fixed needs Root cause, Fix, Verification and
  --commit hashes git resolves), note, recur, set, show, list, triage,
  env, index. 29 unittest cases in scripts/tests/test_buglog.py.
- scripts/git-hooks/pre-commit runs `check --staged`: incomplete staged
  records, a legacy record hand-changed to fixed without the fix-time
  sections, a new record claiming legacy: true, or a stale index refuse
  the commit.
- scripts/gitea-sync.py reads the records: issue body = the record's
  sections plus linked fix commits (origin remote, GITEA_COMMIT_REPO to
  override), and a body hash so an issue's text is refreshed when the
  record changes.
- bug-1866 rewritten to the full standard as the worked example.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
2026-09-28 03:40:11 +00:00

2.9 KiB

id status status_updated status_note component severity timestamp last_seen occurrences files tags related legacy
bug-1504 fixed 2026-09-24 lib crash 2026-08-07T08:00:00Z 2026-09-19T09:00:00Z 1
src/schema/controller.capnp
scheduler-core
task-12.1
capnp-schema
codegen-limitation
sigsegv
uninitialized-memory
controller.capnp
snapshot
bug-1493
bug-1505
true

bug-1504: sched_sim_startup_test SIGSEGV in write_SnapshotData (lib/controller.capnp.c) -- deterministic…

Description

sched_sim_startup_test SIGSEGV in write_SnapshotData (lib/controller.capnp.c) -- deterministic crash inside libCapnC_Runtime's read_ptr/capn_setp, discovered during scheduler-core task 12.1 review remediation (full clean rebuild needed for a libedit dependency swap).

Environment

Not recorded (migrated from buglog.json).

Reproduction

Not recorded (migrated from buglog.json).

Root cause

SnapshotData.internalState was declared :Data in the capnp schema. This codebase's capnpc-c backend silently no-ops Data-field encoding inside generated encode_XXX() composite helpers (documented, deliberate limitation -- see controller.capnp's own prior comment citing ReplayHeader.configHash). But encode_SnapshotData_ptr()'s local struct SnapshotData d; is never zero-initialized before the (partially no-op) encode_SnapshotData() populates it, so the skipped Data field's capn_ptr is left as UNINITIALIZED STACK GARBAGE. write_SnapshotData() then unconditionally capn_setp()'s that garbage onto the wire. This is genuine UB: whether it crashes depends entirely on what garbage bytes land in that stack slot at each call site -- ReplayHeader.configHash has the identical gap but never crashed (lucky garbage); SnapshotData.internalState's stack layout in this one test's call chain was unlucky. A prior 'rm -rf xce.build' full rebuild (needed to pick up a new nix dependency) perturbed the whole binary's layout enough to flip this from dormant to a deterministic, reproducible SIGSEGV.

Fix

Changed SnapshotData.internalState from Data to List(UInt8) in controller.capnp, with a new companion internalStateLen (@11, UInt32) wire field for the maplistcount -- following the exact working precedent of FetchFileReply.content/bytesRead, which this same capnpc-c backend DOES correctly auto-generate real (non-no-op) encode/decode for (capn_new_list8/capn_set8 loop, not a placeholder comment). Updated typemap.h's sched_snapshot_data_t.internal_state_len from size_t to uint32_t to match the wire type, and updated test_e2e_capnp.c's test_snapshot_data_round_trip (which previously worked around the Data no-op with a manual low-level SnapshotData_get/set_internalState accessor) to rely on the now-working ordinary codec bridge instead. No hand-written low-level accessor code needed any more for this field.

Verification

Not recorded (migrated from buglog.json).

References

  • Related: bug-1493, bug-1505