libc: add more signal tests

[etiaro]

RTOS-736

Description

Tests results

Motivation and Context

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (refactoring, style fixes, git/CI config, submodule management, no code logic changes)

How Has This Been Tested?

• Already covered by automatic testing.
• New test added: (add PR link here).
• Tested by hand on: (list targets here).

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing linter checks and tests passed.
• My changes generate no new compilation warnings for any of the targets.

Special treatment

• This PR needs additional PRs to work (list the PRs, preferably in merge-order).
• !syscalls: move signal handling to kernel phoenix-rtos-kernel#670
• !signal: move signal handling to kernel libphoenix#420
• I will merge this PR by myself when appropriate.

[gemini-code-assist]

Summary of Changes

Hello @etiaro, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

I've added a comprehensive suite of new tests to the libc component, primarily focusing on signal handling and the sigaction system call. This includes tests for various signal dispositions, masked signal behavior, handler recursion, and the interaction of sigaction within signal handlers. Additionally, I've included a new test case for pthread_cancel to ensure proper cleanup handler execution.

Highlights

• Pthread Cleanup Test: Added a new test case pthread_cleanup_push_pthread_cancel to verify the correct execution of pthread cleanup handlers when a thread is cancelled.
• Comprehensive Signal Handling Tests: Introduced a new TEST_GROUP(sigaction) with numerous test cases to thoroughly validate the behavior of the sigaction system call, covering signal termination, default ignored signals, unmasking signals with changing actions, handler recursion, and sigaction calls from within signal handlers.
• Signal Test Utilities: Implemented new helper functions (safe_fork, sighandlerRecursive, sighandlerReraise, sighandlerAction) to facilitate the creation of robust and diverse signal handling test scenarios.
• Test Suite Integration: Integrated the newly added sigaction test group into the main libc signal test runner to ensure these new tests are executed as part of the standard test suite.

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[gemini-code-assist]

Code Review

This pull request adds a comprehensive suite of tests for POSIX signals, particularly focusing on sigaction behaviors, and a new test for pthread_cancel with cleanup handlers. The changes are valuable for improving the test coverage of the C library. I've identified a couple of issues in the new test implementations: a race condition that could lead to test flakiness, and a logical flaw in one of the signal tests. My review includes suggestions to address these points to improve the robustness and correctness of the new tests.

[github-actions]

Unit Test Results

9 603 tests  +170   8 996 ✅ +152   51m 31s ⏱️ + 2m 3s
  545 suites ±  0     601 💤 + 12 
    1 files   ±  0       6 ❌ +  6 

For more details on these failures, see this check.

Results for commit 39de784. ± Comparison against base commit f646ce7.

♻️ This comment has been updated with latest results.