tests: runtime: Handle byte order mark for non-ASCII environment of Windows correctly

[cosmo0920]

Especially, cp932 Windows causes compilation failure without appropriate BOM handlings on in_tail and out_syslog runtime tests.

---

Enter [N/A] in the box, if an item is not applicable to your change.

Testing
Before we can approve your change; please submit the following in a comment:

• Example configuration file for the change
• Debug log output from testing the change

• Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• Run local packaging test showing all targets (including any new ones) build.
• Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• Documentation required for this feature

Backporting

• Backport to latest stable release.

---

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

  • Improved handling of files that begin with a UTF-8 byte order mark (BOM), ensuring the initial mode comment is recognized correctly.

• Tests

  • Updated RFC5424 syslog formatter expectations to avoid embedding an invisible UTF-8 BOM directly in string literals, improving test reliability across severity, facility, hostname, appname, procid, msgid, and structured data cases.

[coderabbitai]

📝 Walkthrough

Walkthrough

Runtime tests now add a UTF-8 BOM prefix to one source comment and represent BOM bytes explicitly in RFC5424 syslog expected strings using a shared macro.

Changes

UTF-8 BOM test updates

Layer / File(s)	Summary
Make RFC5424 BOM expectations explicit tests/runtime/out_syslog.c	Defines UTF8_BOM and uses it across RFC5424 syslog expected strings.
Add BOM to test source comment tests/runtime/in_tail.c	Adds a UTF-8 BOM prefix to the file’s leading comment.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Suggested reviewers: edsiper

🚥 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
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.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title matches the main change: adding BOM handling for Windows runtime tests.

✨ 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-save-in_tail-test-case-with-bom

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{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 `@tests/runtime/out_syslog.c`:
- Line 1453: Split the oversized RFC5424 expected string literals near the
affected assertions into adjacent C string literals on multiple lines, including
the occurrences around the referenced expectations. Preserve exact compile-time
concatenation and expected values while keeping each source line within the
project’s 120-character limit.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

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

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: f8237e25-052b-4367-bcc1-461a9418f430

📥 Commits

Reviewing files that changed from the base of the PR and between a4ad88f and bd56507.

📒 Files selected for processing (1)

• tests/runtime/out_syslog.c

[coderabbitai]

📐 Maintainability & Code Quality | 🟡 Minor | ⚡ Quick win

Split the oversized expected strings.

These RFC5424 expectations exceed 120 characters. Split them into adjacent C string literals across multiple lines; compile-time concatenation preserves the exact expected value while following the project’s line-length guideline.

As per coding guidelines, C/C++ lines should target 100 characters and avoid exceeding 120 where avoidable.

Also applies to: 1509-1509, 1566-1566

🤖 Prompt for 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.

In `@tests/runtime/out_syslog.c` at line 1453, Split the oversized RFC5424
expected string literals near the affected assertions into adjacent C string
literals on multiple lines, including the occurrences around the referenced
expectations. Preserve exact compile-time concatenation and expected values
while keeping each source line within the project’s 120-character limit.

Source: Coding guidelines