docs/clang_tidy.md

# Clang Tidy

[TOC]

## Danger, Will Robinson!

Support for `clang-tidy` in Chromium is very experimental, and is somewhat
painful to use. We are exploring making it easier and integrating with existing
tools, but aren't there yet. If you don't want to wait and enjoy tinkering,
forge ahead. Otherwise, feel free to turn back now.

## Introduction

[clang-tidy](http://clang.llvm.org/extra/clang-tidy/) is a clang-based C++
“linter” tool. Its purpose is to provide an extensible framework for diagnosing
and fixing typical programming errors, like style violations, interface misuse,
or bugs that can be deduced via static analysis.

## Setting Up

In addition to a full Chromium checkout, you need the clang-tidy binary. We
recommend checking llvm's clang source and building the clang-tidy binary
directly. Instructions for getting started with clang are available from
[llvm](http://clang.llvm.org/get_started.html). You'll need to get llvm,
clang, and the extra clang tools (you won't need Compiler-RT or libcxx).
If you don't have it, you'll also need to install cmake as a part of this
process.

Instead of building with `"Unix Makefiles"`, generate build files for Ninja with
```
cmake -GNinja -DCMAKE_BUILD_TYPE=Release ../llvm
```

Then, instead of using `make`, use ninja to build the clang-tidy binary with
```
ninja clang-tidy
```

This binary will be at (build)/bin/clang-tidy.

If you intend to use the `fix` feature of clang-tidy, you'll also need to build
the `clang-apply-replacements` binary.
```
ninja clang-apply-replacements
```

## Running clang-tidy

Running clang-tidy is (hopefully) simple.
1.  Build chrome normally.\*
```
ninja -C out/Release chrome
```
2.  Generate the compilation database
```
tools/clang/scripts/generate_compdb.py -p out/Release > compile_commands.json
```
3.  Enter the build directory.
```
cd out/Release
```
4.  Run clang-tidy.
```