Last of the five field-parity gaps from the original audit (bug-1678,
bug-1687, bug-1689, bug-1690, bug-1691). set_preason()/clear_preason()
set job.pend_reasons (host/resource-based pending-job explanations), but
persist_job_hook_fun's default: arm only ever captured {jobid, state}.
Neither apply seam restored pend_reasons after a restart.
Reuses the ALREADY-EXISTING JobPendReason/HostBasedReason/ResourceBasedReason
capnp structs -- no schema change needed, unlike bug-1690's WAL_JOB_RUSAGE.
Safety-checked against bug-1690's lesson (RTTI/makeString()-backed fields
need merge-not-replace, not free-and-replace): pend_reasons is plain
malloc/strdup-backed throughout (erase_job_preason is FREEUP()-only,
add_host_preason/add_res_preason use strdup()/calloc()), so a
straightforward free-and-replace is safe here, matching bug-1678/1687's
pattern instead.
New wrinkle beyond the four prior fixes: pend_reasons has a genuine CLEAR
operation, and "trailing bytes present or absent" can't distinguish a
legitimate clear from an old-format payload -- added an explicit presence
byte (0=cleared/adopt NULL, 1=capnp bytes follow), verified by two
dedicated "clear survives restart" tests.
11 new tests in test_wal_job_preason_fact.c; RED/GREEN independently
verified (7 genuine pre-fix failures, one test's own wrong premise about
capnp's garbage-byte behavior caught and corrected during RED/GREEN
iteration). Full controller suite: 1178 tests, 2 failures -- both the
pre-existing, unrelated bug-1561 overlayfs sandbox flake. No ASAN findings.
This closes the field-complete apply parity invariant class the
xce-audit-invariants controller dimension 7 was added for.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AgYRU3zDTqNGV5Jk8aiKLg
Rongsong Shen
d0e5f85aa8