How to use Clang Tidy to automatically correct code

Install

Clang-Tidy is a tool developed and maintained by the Clang/LLVM community. The official documentation can be found at http://clang.llvm.org/extra/clang-tidy/. When running Linux, clang-tidy is usually easy to get via your distribution’s package manager. On Ubuntu Linux:

sudo apt-get install clang-tidy

Additionally you can download directly in the project page.

Introduction

A typical invocation of the command-line tool looks like this:

clang-tidy test.cpp -- -Imy_project/include -DMY_DEFINES ...

Executing it like this, the tool will print a bunch of warnings and notes (if applicable), in exactly the same way Clang/GCC provide diagnostics, too.

The avalaible checkers avaible can be found with the following command:

clang-tidy --list-checks -checks='*' | grep "modernize"
   modernize-avoid-bind
   modernize-deprecated-headers
   modernize-loop-convert
   modernize-make-shared
   modernize-make-unique
   modernize-pass-by-value
   modernize-raw-string-literal
   modernize-redundant-void-arg
   modernize-replace-auto-ptr
   modernize-shrink-to-fit
   modernize-use-auto
   modernize-use-bool-literals
   modernize-use-default
   modernize-use-emplace
   modernize-use-nullptr
   modernize-use-override
   modernize-use-using

To correct the code we can use the command -fix (not all the avalaible checkers have the -fix function). For example to add the missing overrides in the following code:

struct Base {
   virtual void reimplementMe(int a) {}
};
struct Derived : public Base  {
   virtual void reimplementMe(int a) {}
};

We use the next command:

clang-tidy -checks='modernize-use-override' -fix test.cpp -- -std=c++11

Using to correct a whole project

The previous example will work just with a very simple example contained in one file. To correct the whole project we will need to create a json file containing all the file in the project. For that we add the following line to ou configure.sh:

-DCMAKE_EXPORT_COMPILE_COMMANDS=ON                                                       \

This will create a file named compile_commands.json that we will use with the following python script from the LLVM project).

Once we have the script and the json file we can check and fix the whole project by the following way:

run-clang-tidy.py -header-filter='.*' -checks='-*,modernize-use-override' -fix

You can run simmultaneously all the possible modernize commands using the following shell script.

sh modernize.sh