feat: harden BDD target stderr error handler to exit on ERROR severity

[DavidCozens]

Purpose

S11.05 part B (#403) finished green but spent 23 minutes in CI vs the usual 4–5. Per-step timing showed both build-linux-tunable-override and build-freertos-target spent ~16 minutes in the "Initialize containers" step (ghcr.io image pull) — runner cold-cache, not a project regression. Other jobs on the same run using the same image pulled in seconds.

The real concern surfaced by that diagnosis is that pool exhaustion in a BDD wiring scenario would currently fail silently: _Create returns the shared null object, the BDD target keeps running on it, the oracle receives nothing, the scenario times out, and the captured failure is "oracle received 0 of 1" rather than "BDD target died on POOL_EXHAUSTED". Same failure class as part A's STREAM_SENDER default-1 bust (#402).

This PR hardens the BDD-target stderr handler so the silent-drop class becomes a loud, locally-debuggable failure.

Change Description

Bdd/Targets/Common/BddTargetStderrErrorHandler.c now branches on severity:

• severity <= SOLIDSYSLOG_SEVERITY_ERROR (EMERGENCY / ALERT / CRITICAL / ERROR) ⇒ fprintf(stderr, "BDD-TARGET: FATAL: %s\n", message), fflush(stderr), _Exit(3).
• Any other severity (WARNING, etc.) ⇒ existing print-only line, unchanged.

Design notes:

• _Exit (C99 <stdlib.h>) not _exit (POSIX <unistd.h>). The Common/ file is shared by the Windows BDD target as well, so the portable C99 form is required. Same no-atexit / no-stdio-flush semantics — fflush(stderr) is called first so the FATAL marker reaches the wire before the process disappears.
• <= rather than == so EMERGENCY / ALERT / CRITICAL also exit. Library code only emits ERROR/WARNING today, so the forms are equivalent in practice, but <= is the defensible semantics.
• No unit test. The handler is six production lines; a _Exit seam (function-pointer indirection + paired interceptor test) is more abstraction than the change justifies. The honest validation is end-to-end via a BDD scenario that deliberately starves a pool — which doesn't yet exist; raised as a Deferred item in DEVLOG. Compile-time gates carry the rest.

Test Evidence

All local gates green on the branch in the project's dev containers:

• debug — 1188 tests pass
• sanitize (ASan + UBSan) — 1188 tests pass
• clang-debug — 1188 tests pass
• tidy — clean (warnings-as-errors)
• cppcheck — clean
• coverage — clean
• iwyu — clean (invoked as cmake --build --preset iwyu --target iwyu)
• clang-format --dry-run --Werror over Core/Interface Core/Source Tests Bdd/Targets — clean

CI will cover Windows MSVC, FreeRTOS cross/QEMU, and the BDD jobs.

Areas Affected

• Bdd/Targets/Common/BddTargetStderrErrorHandler.c — Tier 3 (BDD targets, best-effort). No production-library impact.
• DEVLOG.md — session entry.

No public-header or Core/ changes.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Enhanced error handling to treat critical error severities as fatal, triggering process termination with a clear status message for improved system robustness.

• Documentation

  • Added documentation detailing error handling hardening improvements and related design decisions.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: bbf791b2-ab41-4481-96df-e1215a2ff897

📥 Commits

Reviewing files that changed from the base of the PR and between 1a79af9 and c637a5d.

📒 Files selected for processing (2)

• Bdd/Targets/Common/BddTargetStderrErrorHandler.c
• DEVLOG.md

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📝 Walkthrough

Walkthrough

The PR hardens the BDD target stderr error handler to treat SOLIDSYSLOG_SEVERITY_ERROR and below as fatal. When such severities are logged, the handler now prints a BDD-TARGET: FATAL marker, flushes stderr, and terminates the process via _Exit(3). Higher severities continue to log without exiting. A new <stdlib.h> include and devlog entry document the change.

Changes

BDD stderr handler fatal exit hardening

Layer / File(s)	Summary
Stderr handler fatal exit implementation and documentation Bdd/Targets/Common/BddTargetStderrErrorHandler.c, DEVLOG.md	StderrErrorHandler adds severity-based branching: severities at or below SOLIDSYSLOG_SEVERITY_ERROR trigger a BDD-TARGET: FATAL message, stderr flush, and process termination via _Exit(3). Higher severities log without exiting. The <stdlib.h> include is added for _Exit, and the change is documented in the devlog with implementation details and deferred questions.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A fatal exit hops so clean,
When errors reach the danger scene,
ERROR down means _Exit time,
No mercy for severity's climb!
BDD-TARGET logs its last goodbye. 🌙

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically summarizes the main change: hardening the BDD target stderr handler to exit on ERROR severity.
Description check	✅ Passed	The description is comprehensive and follows the template structure, covering Purpose, Change Description, Test Evidence, and Areas Affected with substantial detail.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/bdd-target-fatal-exit-on-error

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[github-actions]

☀️   Quality Summary

   🚦   build-linux-gcc: 100% successful (✔️ 1192 passed, 🙈 2 skipped)
   🚦   build-freertos-host-tdd: 100% successful (✔️ 1312 passed, 🙈 2 skipped)
   🚦   build-linux-clang: 100% successful (✔️ 1144 passed, 🙈 2 skipped)
   🚦   sanitize-linux-gcc: 100% successful (✔️ 1144 passed, 🙈 2 skipped)
   🚦   integration-linux-openssl: 100% successful (✔️ 9 passed)
   🚦   integration-windows-openssl: 100% successful (✔️ 9 passed)
   🚦   bdd-linux-syslog-ng: 94% successful (✔️ 46 passed, 🙈 3 skipped)
   🚦   bdd-windows-otel: 90% successful (✔️ 44 passed, 🙈 5 skipped)
   🚦   bdd-freertos-qemu: 73% successful (✔️ 36 passed, 🙈 13 skipped)
   🚦   build-windows-msvc: 100% successful (✔️ 1045 passed, 🙈 1 skipped)
   🚦   build-linux-tunable-override: 100% successful (✔️ 1144 passed, 🙈 2 skipped)
   ⚠️   Clang-Tidy: 6 warnings (normal: 6)
   ⚠️   CPPCheck: No warnings

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Created by Quality Monitor v1.14.0 (#f3859fd). More details are shown in the GitHub Checks Result.