---
id: "bug-1827"
status: "fixed"
status_updated: "2026-09-24"
status_note: ""
component: "scheduler"
severity: "crash"
timestamp: "2026-09-18T07:15:00Z"
last_seen: "2026-09-19T14:30:00Z"
occurrences: 1
files: ["src/scheduler/testsuite/test_core_isolation.c"]
tags: ["scheduler", "core-isolation", "test-coverage-gap", "test_core_isolation", "core_clock", "audit-finding", "discovered-during-xce-audit-invariants"]
related: []
legacy: true
---

# bug-1827: ), while investigating driver state-equivalence for bug-1826. test_core_isolation.c's own header…

## Description
NOT A CRASH -- coverage gap found during an /xce-audit-invariants scheduler run (dimension 2: core module I/O isolation), while investigating driver state-equivalence for bug-1826. test_core_isolation.c's own header comment claims core_clock.c joins ONLY the nm(1) undefined-symbol enforcement layer, not the wall-clock text-scan check -- implying it is still covered by the OTHER two text-scan checks (forbidden #include list, forbidden symbol substrings). In reality, core_clock.c is absent from all three text-scan functions (test_core_never_includes_forbidden_headers(), test_core_never_calls_forbidden_symbols(), and the wall-clock scan), not just the wall-clock one -- no XCE_CORE_CLOCK_C_PATH macro is defined anywhere in test_core_isolation.c or testsuite/meson.build's c_args for that test.

## Environment
_Not recorded (migrated from buglog.json)._

## Reproduction
_Not recorded (migrated from buglog.json)._

## Root cause
core_clock.c was added to the mechanically-enforced sched_core_isolation_lib archive (meson.build) and given a documented single exception (the wall-clock text scan, for its one sanctioned clock_gettime() call), but the two OTHER text-scan functions (forbidden-headers, forbidden-symbols) were never extended to also read core_clock.c's source text -- only core.h/core.c/core_events.c/core_session.c are read by those two checks (via XCE_CORE_H_PATH/_C_PATH/_EVENTS_C_PATH/_SESSION_C_PATH macros; no clock-file variant exists). The nm(1) undefined-symbol layer (which DOES include core_clock.c in the archive) only catches an actual undefined-symbol reference at link time -- it cannot catch a bare forbidden #include (e.g. client.h/netio.h/xceapi.h/delay.h/idgen.h/xce/cluster.h) that resolves to no undefined symbol (a macro-only or inline-only header), so the doc comment's implied coverage is narrower in practice than stated. No evidence found that core_clock.c's actual current content violates isolation today -- this is a gap in what the mechanism would CATCH if it did, not a confirmed live violation.

## Fix
FIXED (2026-09-19). Added XCE_CORE_CLOCK_C_PATH (testsuite/meson.build c_args for sched_core_isolation_test, mirroring the existing XCE_CORE_H_PATH/_C_PATH/_EVENTS_C_PATH/_SESSION_C_PATH pattern) and extended both test_core_never_includes_forbidden_headers() and test_core_never_calls_forbidden_symbols() (test_core_isolation.c) to also scan core_clock.c -- it remains excluded ONLY from the wall-clock scan (test_core_never_calls_wallclock_functions), for the same sanctioned-single-clock_gettime()-call reason as before. TDD: confirmed RED by temporarily inserting #include "netio.h" into core_clock.c and rebuilding -- the extended test correctly failed with the message "core_clock.c directly includes forbidden header '#include "netio.h"'" (test_core_isolation.c:226) while every other test stayed green (84/85); reverted (git diff confirms core_clock.c byte-identical to HEAD) and reconfirmed GREEN (85/85). No live violation existed in core_clock.c -- this closes the coverage gap the mechanism itself had, matching what its own header/doc comments already claimed.

## Verification
_Not recorded (migrated from buglog.json)._

## References
_Not recorded (migrated from buglog.json)._