codeguard-c

C Codeguard Gate

Goal: turn "looks fine" into repeatable tool evidence, and honestly distinguish pass, fail, unverifiable, and planned.

Start in 30 seconds

1. At the repository root, confirm that 无专用标记文件 or the target file exists.
2. Probe tools:clang-tidy --version。
3. First do a read-only check:bash -c 'find . -name '"'"'*.c'"'"' -o -name '"'"'*.h'"'"' | xargs -r clang-tidy --quiet'。
4. Classify results as: code violations, missing configuration, missing tools, tool internal errors.
5. Only perform safely fixable items:clang-format -i '{file}'。
6. Rerun lint, and run the project's existing test/build gates.

You can directly ask:

• "Check this C project, don't modify anything first, and give me a classification of lint failures."
• "Only fix C formatting issues; list semantic issues first."
• "Verify C lint, test, and build evidence before committing."

Capability boundaries

✅ Good at handling

1. Based on .c, .h and project markers, identify the C workspace.
2. Run clang-tidy --quiet '{file}' and preserve exit codes, scope, and tool versions.
3. Distinguish formatting, static rule, configuration, dependency, and environment failures.
4. Use clang-format -i '{file}' to handle reversible issues and rescan.
5. Report local results in layers alongside CI/build/test evidence.

⚠️ Requires conditions

1. The target tool must already be installed and its version compatible with project constraints.
2. Must be run from the correct repository or module root directory.
3. If the project has custom configuration, the committed configuration prevails.
4. Whether generated code, vendor, and cache directories are scanned must follow repository rules.

❌ Not applicable

1. Do not treat formatter pass as compilation, test, or security audit pass.
2. Do not silently install tools, upgrade dependencies, or modify team rules.
3. Do not use suppress/ignore/raising thresholds to hide real problems.
4. Do not claim "check passed" when tools or configuration are missing.

When to use

• The user requests checking or fixing C code standards.
• AI modified .c, .h, and pre-commit verification is needed.
• CI shows failures related to clang-tidy --quiet '{file}' .
• Need to determine whether a problem can be fixed automatically or must be handled manually.

When not to use

• When the main task is learning language syntax, framework design, or business modeling, use the corresponding language professional skill instead.
• When the main task is dependency vulnerabilities, security auditing, or license governance, use a dedicated security skill.
• When the user only asks to explain one error and there is no project context, first give a local explanation and do not claim the repository is all green.

Data and security

This skill does not collect, upload, send, or store user code and credentials. By default, it only reads local repository configuration and runs local tools; it does not install dependencies over the network, and does not record tokens, passwords, or private source code. Check the diff before any automatic fix; destructive or large-scale changes must be explicitly confirmed by the user.

Execution contract

Project	Current facts
Status	stable(since Codeguard V0.4)
File extensions	.c, .h
Project marker	No dedicated marker file
Integration configuration	Based on the repository's existing configuration
Tool preparation	clang-tidy + clang-format
Detection commands	使用命令查找与项目配置检查
lint	clang-tidy --quiet '{file}'
format/fix	clang-format -i '{file}'
Project-level gate	bash -c 'find . -name '"'"'*.c'"'"' -o -name '"'"'*.h'"'"' | xargs -r clang-tidy --quiet'

Standard Workflow

Step 1: Determine the real scope

Confirm the repository root, module roots, generated directories, vendor directories, and user-specified files. For multi-module projects, first list the modules that will be scanned; do not guess based on the current directory.

Step 2: Read the project contract

Read the actual commands in Based on the repository's existing configuration and CI. Repository configuration takes precedence over this skill's examples; if the two conflict, report the differences first.

Step 3: Detect tools and versions

Run 对应工具 --version. Missing tools, incompatible versions, or configurations that fail to load are all recorded as "unable to verify", not as passed.

Step 4: Perform read-only checks

Run bash -c 'find . -name '"'"'*.c'"'"' -o -name '"'"'*.h'"'"' | xargs -r clang-tidy --quiet', recording the command, working directory, exit code, tool version, and the first actionable error.

Step 5: Failure classification

Type	Typical signal	Handling
Format	Indentation, whitespace, import order	Formatter allowed, then check the diff
Static rules	unused, complexity, naming, dangerous APIs	Minimal semantic fix, no bulk guessing
Configuration	parser/config/schema not found	Fix the integration or report prerequisites
Environment	command not found, version conflict	Report installation/version requirements, do not install silently
Tool internal error	crash, timeout, parser exception	Preserve the original evidence, narrow the reproduction scope

Step 6: Controlled fixes

Prefer to run clang-format -i '{file}'. Only handle issues that are certain and reversible; dependency upgrades, rule exemptions, generated files, and business semantic changes must be explained separately.

Step 7: Verification loop

Re-run the same lint command, then run the project's existing tests and build. Only write "passed" when the command, scope, and exit code are all clear; otherwise write "not run" or "unable to verify".

Rules

1. Re-verify with the same command: after fixing, the original command that triggered the failure must be re-run.
2. Layered evidence: lint, format, compile, test, and security are reported separately.
3. Minimal changes: do not refactor along the way, and do not expand style fixes into business rewrites.
4. Configuration first: do not override the project's existing ignore, dialect, target, or version constraints.
5. No fabrication: tools not run, configurations not seen, and platforms not verified must be clearly marked.

Output template

C Codeguard 结果
- 范围：<仓库/模块/文件>
- 工具：<名称与版本>
- 命令：<实际命令>
- 状态：PASS / FAIL / UNVERIFIED / PLANNED
- 发现：<按格式/规则/配置/环境分类>
- 修改：<文件与原因；无修改写 none>
- 复验：<命令、退出码>
- 未验证：<测试/构建/平台差异>

Gotchas

1. Missing tools are not a pass — must output UNVERIFIED and a clear preparation method.
2. formatter is not a linter — all-green formatting cannot cover static rules or compilation errors.
3. The root directory determines the result — running in the wrong module may miss detections or load the wrong configuration.
4. Placeholders are not literal arguments — {file} must be replaced with real, authorized paths.
5. Auto-fixes may expand the diff — after fixing, review the diff first, then run the regression gate.
6. Generated and vendor directories need an explicit policy — do not casually scan or modify third-party content across the whole repository.

Domain pitfalls and fixes

1. Domain pitfalls — clang-tidy needs reliable compilation arguments; for complex projects, prefer providing compile_commands.json。

When information is insufficient

Do not just say "please provide more information". First give a safe read-only inspection plan, and list the specific items that still need confirmation:

1. repository/module root directory;
2. target tools and versions;
3. project configuration files;
4. the authoritative commands in CI;
5. whether auto-fixes are allowed.

FAQ

Q1: If the tool is not installed, can we conclude the code is fine? No. The status must be UNVERIFIED。

Q2: Can I automatically add ignore or suppression? No. An exemption is only allowed when the user explicitly accepts it and the reason is recorded.

Q3: Why does it still fail after formatting? The formatter only covers formatting; static rules, configuration, compilation and tests still need to be handled separately.

Q4: Should generated code be scanned? By default follow the repository configuration; if there are no rules, exclude generated/vendor first, then explain to the user.

Q5: How can I avoid changing too much at once? Fix in batches by failure category and file first, and rerun the original command and review the diff for each batch.

Q6: If it passes locally, can I say CI will pass? No. You also need to align with CI's versions, environment variables, operating system and command scope.

Load resources on demand

• When encountering exit codes, failure classification or exemption decisions, read references/rules/gate-rules.md。
• When you need to check this language's registry, toolchain and project configuration, read references/tooling/toolchain.md。
• When you need copyable task examples, read by scenario examples/, there is no need to load them all at once.