CLinters 1.1.1

pre-commit hooks for C linters

pre-commit hooks

This is a pre-commit hooks repo that integrates five C/C++ linters:

clang-format, clang-tidy, oclint, uncrustify, cppcheck

Many of these linters will return 0 on error, which pre-commit will then mark as passing. Additionally, pre-commit has a bug where arguments after -- are dropped. This repo's hooks for each command will fail correctly and honor all -- arguments.

This repo is available in both python and bash. To use a language, use rev: $lang in your .pre-commit-config.yaml. Master is set to python as the default as it is easier to maintain and troubleshoot.

Example Usage

With int main() { int i; return 10; } in a file err.cpp, all five linters should fail on commit:

Using clang-format 8.0.0; clang-tidy 8.0.0; oclint 0.13

The above uses this .pre-commit-config.yaml:

fail_fast: false
repos:
  - repo: https://github.com/pocc/pre-commit-hooks
    rev: python
    hooks:
      - id: clang-format
        args: [--style=Google]
      - id: clang-tidy
        args: [-checks=clang-diagnostic-return-type]
      - id: oclint
        args: [-enable-clang-static-analyzer, -enable-global-analysis]
      - id: uncrustify
      - id: cppcheck
        args: [--enable=all]

Note that for your config yaml, you can supply your own args or remove the args line entirely, depending on your use case.

Using the Hooks

Python3.6+ is required to use these hooks as all 5 invoking scripts are written in it. As this is also the minimum version of pre-commit, this should not be an issue.

Installation

You will need to install these utilities in order to use them. Your package manager may already have them. Below are the package names for each package manager, if available:

• apt install clang clang-format clang-tidy uncrustify cppcheck [1] [2]
• yum install llvm uncrustify cppcheck [2]
• brew install llvm oclint uncrustify cppcheck [3]
• choco install llvm uncrustify cppcheck [4]

[1]: clang is a required install for clang-format or clang-tidy to work.

[2]: oclint takes a couple hours to compile. I've compiled and tarred oclint-v0.15 for those using linux who want to skip the wait (built on Ubuntu-18.04). You can also download the older oclint-v0.13.1 for linux from oclint's github page (see releases).

[3]: Depending on your brew installation, you may need to install oclint with brew cask install oclint.

[4]: oclint is not available on windows.

If your package manager is not listed here, it will have similar names for these tools. You can build all of these from source.

Hook Info

Hook Info	Type	Languages
clang-format	Formatter	C, C++, ObjC
clang-tidy	Static code analyzer	C, C++, ObjC
oclint	Static code analyzer	C, C++, ObjC
uncrustify	Formatter	C, C++, C#, ObjC, D, Java, Pawn, VALA
cppcheck	Static code analyzer	C, C++

Hook Option Comparison

Hook Options	Fix In Place	Enable all Checks	Set key/value
clang-format	-i
clang-tidy	--fix-errors [1]	-checks=* -warnings-as-errors=* [2]
oclint		-enable-global-analysis -enable-clang-static-analyzer	-rc=<key>=<value>
uncrustify	--replace --no-backup [3]		--set key=value
cppcheck		-enable=all

[1]: -fix will fail if there are compiler errors. -fix-errors will -fix and fix compiler errors if it can, like missing semicolons.

[2]: Be careful with -checks=*. can have self-contradictory rules in newer versions of llvm (9+): modernize wants to use trailing return type but Fuchsia disallows it. Thanks to @rambo.

[3]: By definition, if you are using pre-commit, you are using version control. Therefore, it is recommended to avoid needless backup creation by using --no-backup.

Enforcing linter version with --version

Some linters change behavior between versions. To enforce a linter version 8.0.0, for example, add --version=8.0.0 to args: for that linter. Note that this is a pre-commit hook arg and will be filtered before args are passed to the linter.

Compilation Database

clang-tidy and oclint both expect a compilation database. Both of the hooks for them will ignore the error for not having one.

You can generate with one cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON ... if you have a cmake-based project.

The '--' doubledash option

Options after -- like -std=c++11 will be interpreted correctly for clang-tidy and oclint. Make sure they sequentially follow the -- argument in the hook's args list.

Standalone Hooks

If you want to have predictable return codes for your C linters outside of pre-commit, these hooks are available via PyPI. Install it with pip install CLinters. They are named as $cmd-hook, so clang-format becomes clang-format-hook.

If you want to run the tests below, you will need to install them from PyPI or locally with pip install ..

Development

Testing

To run the tests and verify clang-format, clang-tidy, and oclint are working as expected on your system, use pytest --runslow --internal -vvv. This will work on both bash and python branches.

Testing is done by using pytest to generate 76 table tests (python branch) based on combinations of args, files, and expected results.

The default is to skip most (41/76) tests as to run them all takes ~60s. These pytest options are available to add test types:

• --runslow: oclint tests, which take extra time
• --internal: Internal class tests to ensure internal/shell APIs match

Note: You can parallelize these tests with pytest-xdist. Adding -n 32 to the command creates 32 workers and divides runtime by ~6x in my testing.

To run all tests serially, run pytest -x -vvv --internal --runslow like so:

pre-commit-hooks$ pytest -x -vvv --internal --runslow
============================= test session starts ==============================
platform darwin -- Python 3.7.6, pytest-5.4.1, py-1.7.0, pluggy-0.13.1 -- /usr/local/opt/python/bin/python3.7
cachedir: .pytest_cache
rootdir: /Users/pre-commit-hooks/code/pre-commit-hooks, inifile: pytest.ini
collected 76 items

tests/test_hooks.py::TestHooks::test_run[run_cmd_class clang-format on /Users/pre-commit-hooks/code/pre-commit-hooks/tests/files/ok.c] PASSED [  3%]
tests/test_hooks.py::TestHooks::test_run[run_cmd_class clang-tidy on /Users/pre-commit-hooks/code/pre-commit-hooks/tests/files/ok.c] PASSED [  7%]
...

============================= 89 passed in 61.86s ==============================

Why have a script when your hook could be $command "$@"?

shellcheck keeps things simple by relaying arguments as shellcheck "$@". This is not possible with several C/C++ linters because they exit 0 when there are errors. pre-commit registers failures by non-zero exit codes, which results in false "passes".

Additional Resources

clang-format

• Official Docs
• clang-format Guide - a good overview and a great place to get started
• clang-format Configurator - Website to interactively design your config while
• clang-format Options Explorer - Website to interactively understand various options
• Source Code

clang-tidy

• Official Docs
• clang-tidy guide - Good place to start
• Example usage - Explanation of how to use clang-tidy by the creators of Kratos
• Add your own checks - Function names must be awesome!
• Source Code

oclint

• Official Docs
• Fastlane Integration
• Source Code

uncrustify

• Official Docs
• Getting Started with Uncrustify
• Source Code

cppcheck

• Official Docs
• Using Cppcheck
• Source Code

License

Apache 2.0