parser: Handle too long time string on parsing

[cosmo0920]

If time part of the length too long for the fixed slot of parsed time element, we need to allocate a dynamic slot of parsed time element.

Closes #11665.

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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

  • More reliable timestamp parsing for extremely long fractional seconds, preserving subsecond precision and avoiding crashes.
  • Safer handling of oversized timestamp inputs to prevent errors and improve stability on edge cases.

• Tests

  • Added unit tests validating long fractional-second parsing and rejection of oversized input lengths.

[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: 88746832-3e57-4ff0-b23b-1315a9ad49c2

📥 Commits

Reviewing files that changed from the base of the PR and between 886b78c and 72665f3.

📒 Files selected for processing (2)

• src/flb_parser.c
• tests/internal/parser.c

🚧 Files skipped from review as they are similar to previous changes (2)

• tests/internal/parser.c
• src/flb_parser.c

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📝 Walkthrough

Walkthrough

Updated flb_parser_time_lookup() to use a heap-allocated buffer when the fixed 64-byte stack buffer is insufficient, added overflow/alloc guards and explicit frees on all early returns, and added tests covering long fractional seconds and oversized length rejection.

Changes

Cohort / File(s)	Summary
Time parser implementation src/flb_parser.c	Replace fixed 64-byte stack buffer with selectable buf/buf_size and heap time_buf when needed; add INT_MAX/SIZE_MAX overflow checks, allocation failure handling, and ensure flb_free(time_buf) on all failure and success paths. Update strptime inputs to use buf and time_len.
Parser tests tests/internal/parser.c	Add test_parser_time_lookup_long_fraction() and test_parser_time_lookup_reject_oversized_length(); include additional headers (math.h, float.h, limits.h) and register new tests in TEST_LIST.

Sequence Diagram(s)

(omitted — changes are localized to a single function and tests, not a multi-component flow)

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• #11677 — Modifies flb_parser_time_lookup() in the same file (related change addressing timezone selection for year-less timestamps).

Suggested reviewers

• edsiper

Poem

🐰 I nibbled at a long time string,
It grew beyond my 64-byte ring,
I dug up a heap,
No more parse weep,
Now fractions dance and logs can sing 🎶

🚥 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
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title 'parser: Handle too long time string on parsing' clearly summarizes the main change: implementing dynamic buffer allocation to handle time strings longer than the fixed buffer.
Linked Issues check	✅ Passed	The PR directly addresses issue #11665 by implementing dynamic buffer allocation in flb_parser_time_lookup() to prevent 'time string length is too long' errors and adding test cases for long fractional seconds and oversized input lengths.
Out of Scope Changes check	✅ Passed	All changes are focused on the parser functionality: flb_parser_time_lookup() implementation improvements in src/flb_parser.c and corresponding test additions in tests/internal/parser.c, with no unrelated modifications.

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✨ Finishing Touches

📝 Generate docstrings

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🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch cosmo0920-handle-too-long-time-on-parsing

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