tests: runtime: Plug a SEGV occurrence on macOS

[cosmo0920]

Fixed the SEGV in tests/runtime/core_routes.c:72.

Cause: macOS calculated olimit from RLIMIT_NOFILE—419,430 on this host—then indexed a 257-element stack array. The limit is now capped to the array capacity.

Verification passed:

• Target rebuild
• bin/flb-rt-core_routes -v
• Focused ctest -R '^flb-rt-core_routes$'
• Low-descriptor case with ulimit -n 256

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Testing
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Backporting

• Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

Summary by CodeRabbit

• Bug Fixes
  • On macOS, output instance limits are now properly capped to prevent creating more instances than supported.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 94d7d6ee-471a-43a1-b77d-bf30c0d89985

📥 Commits

Reviewing files that changed from the base of the PR and between 6315162 and a948e78.

📒 Files selected for processing (1)

• tests/runtime/core_routes.c

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📝 Walkthrough

Walkthrough

The macOS runtime route test now caps olimit at the output_instances array capacity when the file-descriptor limit is higher.

Changes

macOS output instance limit

Layer / File(s)	Summary
Clamp output instance capacity tests/runtime/core_routes.c	The test caps olimit at the output_instances array capacity when required.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Merge Risk: ⚪ Minimal · up to a948e

The change caps the macOS-derived descriptor limit to the test array capacity, preventing the reported test crash without changing product runtime behavior; no actionable merge-blocking risk remains after normal checks and review.

Possibly related PRs

• fluent/fluent-bit#11592: Adds the macOS olimit handling that this change further constrains.

Suggested reviewers: edsiper

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the macOS SEGV fix in the runtime tests, which matches the main change.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch cosmo0920-plug-segv-on-core_routes-on-macos

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