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debug-with-valgrind

Testing & Quality
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Debug crashes, segfaults, and memory errors using valgrind integration with nextest through pre-configured profiles

QUICK START

How to use this skill

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  1. Open your project in Codex.
  2. Copy the prompt below and paste it into your agent.
  3. Review the proposed files and risks before you approve installation.
Prompt to paste
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Source SKILL.md: https://github.com/facet-rs/facet/blob/HEAD/.claude/skills/debug-with-valgrind/SKILL.md

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First, summarize what it does, its dependencies, license status if identifiable, and any risks. Show the exact files you propose to add under .agents/skills/debug-with-valgrind/. Do not write files or run scripts until I approve.

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Copying this prompt does not install or run the skill. Review third-party files before use. Codex skill guide

Debugging with Valgrind + Nextest

When you encounter crashes, segfaults, or memory errors in tests, use valgrind for proper debugging.

Quick Usage

# Run a specific test under valgrind
cargo nextest run --profile valgrind -p PACKAGE --test TEST_FILE TEST_NAME

# Example
cargo nextest run --profile valgrind -p facet-format-json --test jit_deserialize test_jit_option_some

How It Works

The project has valgrind pre-configured in .config/nextest.toml:

  1. Wrapper script: Defined as [scripts.wrapper.valgrind]

    • Command: valgrind --leak-check=full --show-leak-kinds=all ...
    • Automatically wraps test execution

  2. Profile: [profile.valgrind] applies the wrapper to all tests on Linux

  3. Running: Use --profile valgrind flag with nextest

Benefits

  • ✅ Automatic setup - no manual valgrind commands needed
  • ✅ Proper configuration - leak checking, error codes pre-configured
  • ✅ Integrated - works with nextest filtering and test selection
  • ✅ Clean output - nextest captures and formats valgrind output

Don't Do This

❌ Running valgrind manually: valgrind ./target/debug/deps/test-binary ❌ Using raw --no-run + valgrind commands ❌ Playing hunt-the-segfault without proper tools

Do This Instead

✅ Use the pre-configured profile: cargo nextest run --profile valgrind <filters> ✅ Let nextest handle the wrapper script integration ✅ Get clean, actionable valgrind output immediately

Debugging Workflow

  1. Test crashes with SIGSEGV
  2. Run: cargo nextest run --profile valgrind -p PACKAGE --test FILE TEST_NAME
  3. Valgrind shows exact line where invalid read/write occurs
  4. Fix the bug
  5. Verify with regular tests

See Also