feat: install the SolidSyslog error handler

[DavidCozens]

Pull request

What this stage adds

Nothing in the library fails loudly. A _Create that cannot succeed returns a Null
object and carries on, so a logger that has silently stopped looks exactly like
one with nothing to say. The handler is what tells them apart, and it goes in
before the first _Create rather than after something looks wrong.

Flash +404 B
RAM +8 B

The handler prints to the same console as everything else, so a fault lands in
the run report next to the rest of what the device did. It names the four
lifecycle categories a misconfigured integration raises and prints the rest
numerically — a device reacting to those would switch on the range, not the text.

That is 404 bytes for something this device may never use. It buys the
difference between a silent failure and a sentence, which is worth more than the
bytes on anything that has to be trusted to report.

Files

 CMakeLists.txt                  |  2 +
 README.md                       | 10 +++--
 app/main.c                      |  4 ++
 app/syslog/SyslogErrorHandler.c | 89 +++++++++++++++++++++++++++++++++++++++++
 app/syslog/SyslogErrorHandler.h | 15 +++++++
 measurements/error-handler.csv  | 13 ++++++
 measurements/stages.tsv         |  1 +
 run-report.md                   | 30 +++++++-------
 8 files changed, 145 insertions(+), 19 deletions(-)

Checklist

• The diff touches build infra (1 file(s)) — see Files above; deliberate for this stage.
• measurements/error-handler.csv committed.
• Row added to measurements/stages.tsv.
• README regenerated: python3 scripts/gen-cost-table.py.
• ./run.sh green (build + QEMU + baseline self-check) — run-report.md committed.

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Context for review: 2 of 21 sequential single-commit PRs replaying the integration on top of the Baseline root. Each lands green and reviewed before the next is built on it, because a change to an early commit would force every commit above it to be re-run and re-measured.

Summary by CodeRabbit

• New Features

  • Added startup error handling for system logging.
  • Syslog errors now report readable severity and category information in the device console.
  • Unrecognized error categories remain visible through their numeric values.

• Documentation

  • Updated staged integration guidance to describe the error-handler stage and its resource impact.
  • Refreshed run-report measurements and validation results for the new stage.

[coderabbitai]

📝 Walkthrough

Walkthrough

The application adds a syslog error handler module, registers it before object creation, includes it in the baseline build, and updates documentation and measurement reports for the new error-handler stage.

Changes

Syslog error handler

Layer / File(s)	Summary
Error handler implementation app/syslog/SyslogErrorHandler.h, app/syslog/SyslogErrorHandler.c	Adds the installer API, severity and category mappings, null-safe event formatting, and registration through SolidSyslog_SetErrorHandler.
Startup and build integration CMakeLists.txt, app/main.c	Compiles the handler, adds its include directory, and installs the callback before the first application object creation.
Stage documentation and measurements README.md, run-report.md	Renames the stage to “Error handler” and updates cost, ELF-size, runtime metrics, and self-check data.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant main
  participant SyslogErrorHandler
  participant SolidSyslog
  participant Console
  main->>SyslogErrorHandler: Install before first _Create
  SyslogErrorHandler->>SolidSyslog: Register OnSyslogError
  SolidSyslog->>SyslogErrorHandler: Report error event
  SyslogErrorHandler->>Console: Print formatted error

Loading

Possibly related PRs

• cososo-ltd/solid-syslog-example#10: Adds the same error-handler module and early startup wiring.
• cososo-ltd/solid-syslog-example#28: Adds the SolidSyslog build and linking prerequisites used by the handler.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% 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 states the main change: installing the SolidSyslog error handler.
Description check	✅ Passed	The description matches the template with a 'What this stage adds' section and a filled checklist covering measurements, README regeneration, and run.sh.
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.

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch stage/error-handler

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_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@run-report.md`:
- Around line 52-62: Update the Self-check results in run-report.md so
measurements only receive “OK” when actual and expected values match exactly;
otherwise report a mismatch or fail the check. Regenerate
measurements/error-handler.csv and the report from the same build so
mbedtls_peak, mbedtls_free, and lwip_pbufs_free no longer show inconsistent
values as successful.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: c6162096-2a8e-42b7-8ce9-5f8f85495da8

📥 Commits

Reviewing files that changed from the base of the PR and between 3461555 and 4aa5e5e.

⛔ Files ignored due to path filters (2)

• measurements/error-handler.csv is excluded by !**/*.csv
• measurements/stages.tsv is excluded by !**/*.tsv

📒 Files selected for processing (6)

• CMakeLists.txt
• README.md
• app/main.c
• app/syslog/SyslogErrorHandler.c
• app/syslog/SyslogErrorHandler.h
• run-report.md