pre-commit hooks

This is a pre-commit hooks repo that integrates C/C++ linters/formatters to work with CMake-based projects.

clang-format, clang-tidy, cppcheck, cpplint, lizard and iwyu

It is largely based on the work found here. The main difference with POCC's pre-commit hooks is that the ones from this repository will do a CMake configuration step prior to running any pre-commit hooks. This is done in order to have CMake generate the compilation database file that can then be used by the various hooks (using the -DCMAKE_EXPORT_COMPILE_COMMANDS=ON CMake option).

This repository is only has Python-based pre-commit hooks.

Current known issues

1. Currently, the hooks that depend on having a compilation database generated by CMake (e.g. clang-tidy, cppcheck) are not working on Windows if you are not using the Ninja or Makefile generators.

2. Currently, arguments set in a TOML configuration file (pyproject.toml, cmake_pc_hooks.toml or else) are applied to all hooks. Future improvements may allow to customize arguments on a per-hook basis.

Example usage

Assuming that you have the following directory structure for your projects

root
├── .pre-commit-config.yaml
├── CMakeLists.txt
└── src
    └── err.cpp

with the following file contents:

.pre-commit-config.yaml

repos:
  - repo: https://github.com/Takishima/cmake-pre-commit-hooks
    rev: v1.8.0
    hooks:
      - id: clang-format
      - id: clang-tidy
        args: [--checks=readability-magic-numbers,--warnings-as-errors=*]
      - id: cppcheck
      - id: include-what-you-use

CMakeLists.txt

cmake_minimum_required(VERSION 3.15)
project(LANGUAGE CXX)
add_library(mylib STATIC src/err.cpp)

src/err.cpp

#include <string>
int main() { int i; return 10; }

Running pre-commit on the above project will lead to an output similar to this one:

$ pre-commit run --all-files
clang-format.............................................................Failed
- hook id: clang-format
- exit code: 1

src/err.cpp
====================
<  int main() { int i; return 10; }
---
>  int main() {
>    int i;
>    return 10;
>  }

clang-tidy...............................................................Failed
- hook id: clang-tidy
- exit code: 1

/tmp/temp/src/err.cpp:2:28: error: 10 is a magic number; consider replacing it with a named constant [readability-magic-numbers,-warnings-as-errors]
int main() { int i; return 10; }
                           ^

cppcheck.................................................................Failed
- hook id: cppcheck
- exit code: 1

/tmp/temp/src/err.cpp:2:18: style: Unused variable: i [unusedVariable]
int main() { int i; return 10; }
                 ^
include-what-you-use.....................................................Failed
- hook id: include-what-you-use
- exit code: 1

Problem with /usr/local/bin/iwyu_tool.py: Include-What-You-Use violations found

/tmp/temp/src/err.cpp should add these lines:
/tmp/temp/src/err.cpp should remove these lines:
- #include <string>  // lines 1-1
The full include-list for /tmp/temp/src/err.cpp:
---

Note that your mileage may vary depending on the version of the tools. The example above was generated using clang-format 12.0.0, clang-tidy 12.0.0, cppcheck 2.4.1 and include-what-you-use 0.16.

Using the Hooks

Python 3.8+ is required to use these hooks as all 3 invoking scripts are written in it. As this is also the minimum version of pre-commit, this should not be an issue.

Running multiple hooks in parallel is currently supported by using the fastener Python package. If the hooks are run in parallel, only one of the hooks will run the CMake configure step while the others will simply wait until the call to CMake ends to continue. In the case where the hooks are run serially, all the hooks will be running the CMake configure step. However, if nothing changed in your CMake configuration, this should not cost too much time.

Installation

For installing the various utilities, refer to your package manager documentation. Some guidance can also be found here.

Hook Info

Hook options

Since v1.1.0 all hooks that depend on a compilation database (e.g. clang-tidy, cppcheck, include-what-you-use) will attempt to generate a CMake build directory before running the actual command.

These hooks accept all the most common CMake options:

One important thing to note (particularly for those that intend to use this on CIs), you may specify the build directory argument (-B) multiple times. The hooks will then simply cycle through all of the values provided and choose the first directory that contains a configured CMake project (by looking at the presence of the CMakeCache.txt file). This may be useful if you already have a build directory available somewhere that you would like to reuse. In the case where none of the provided options is viable, the first one will automatically be selected as the build directory.

In addition to the above CMake options, the hooks also accept the following:

NB: by specifying --all-at-once the linter/formatter command will only be called once for all the files instead of calling the command once per file.

NB: Since v1.6.0, the --debug command line argument has been removed. Use the LOGLEVEL environment variable instead to control the level of verbosity of each of the commands. To show all debug messages, set LOGLEVEL=DEBUG in your environment variables when running the hooks.

NB: by specifying --read-json-db the hook will read the list of files from the compile_commands.json generated by CMake and will append those files to the list of files to process regardless of the list of files otherwise passed on the command line.

NB: by specifying --no-cmake-configure the hook will not attempt to create a compilation database by using CMake. However, if one is present, then it will be used by the relevant hooks.

Usage example:

repos:
- repo: https://github.com/Takishima/cmake-pre-commit-hooks
  rev: v1.8.0
  hooks:
    - id: cppcheck
      args: [-DBUILD_TESTING=ON,
             --unix="-DCMAKE_CXX_COMPILER=g++-10",
             --win="-DCMAKE_CXX_COMPILER=cl.exe"
             -Bpath/to/build_dir,
             -Bpath/to/other_build_dir,
             -Spath/to/src_dir
             ]

In the example above, the any hooks requiring a compilation database will first search for a build directory path/to/build_dir and then path/to/other_build_dir. If any of those is deemed valid (ie. is a CMake build directory that contains some CMake cache files), then it will be used. If none qualify, the hooks will default to using path/to/build_dir as a build directory, creating it as necessary.

Also, builds on Linux and MacOS will set the C++ compiler to g++-10, while builds on Windows will be using cl.exe. This is done by looking at the value returned by platform.system().

TOML support

Since v1.9.0, the hooks support loading the CLI arguments from TOML files. This can be used to configure all the hooks for a particular repository using either of:

1. pyproject.toml
2. cmake_pc_hooks.toml
3. TOML file specified using --config=/path/to/file.toml
4. Command line arguments

Note that each step in the above list is overridden by the steps that happen after it. For example, CLI arguments will always override any arguments read from any TOML file.

A good place to start if you plan on creating a TOML configuration file is to use the hooks using the CLI arguments as you would normally and then run the hook manually and with the addition of --dump-toml. This will output a TOML-formatted configuration on the standard output for all the parameters that diverge from their default values.

For example, running the following command (assuming that no valid TOML configuration exists):

cmake-pc-clang-format-hook tests/cmake_bad/bad.cpp  --dump-toml -B /tmp/build -S source -Wdev --no-automatic-discovery

will result in the following output:

automatic_discovery = false
source_dir = "source"
build_dir = [ "/tmp/build",]
dev_warnings = true

CMake configured file detection

Since v1.9.0, the hooks support the use of CMake with trace mode enabled in order to keep track of files that are generated using calls to the configure_file(...) CMake function. If --detect-configured-files is specified on the command line (or in some TOML configuration file), the hooks will attempt to locate those generated files and automatically add them to the list of processed files for any hook invocation.

Hook Option Comparison

[^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=*; some checks can have self-contradictory rules in newer versions of LLVM (9+). For example, modernize wants to use trailing return type but Fuchsia disallows it.

The '--' doubledash option

Options after -- like -std=c++11 will be interpreted correctly for clang-tidy. 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 cmake-pre-commit-hooks. They are named as cmake-pc-$cmd-hook, so clang-format becomes cmake-pc-clang-format-hook.