Integrate Clang-Tidy into CMake

Reading time ~2 minutes

Clang-Tidy is a really great tool that does static code analysis on your code. To be honest I’ve become a much better C++ developer thanks to Clang-Tidy.

My favorite IDE, QtCreator, has something called Clang-Code-Model which is a plugins that runs in the background and in real-time displays things that can be changed. QtCreator also has a tool which can run Clang-Tidy on your project to list potential problems. All this is very nice and makes both you and your code better. But there is one thing missing - integrate into your build.

So I thought I should write a bit on how you can implement Clang-Tidy into your CMake-based project in a really simple way. The goal is that we run Clang-Tidy on the files we compile and not the complete project. The reason for this is speed and also to “force” all team-members to use it.

CMake and Clang-Tidy

Since version 3.7.2 of CMake there is a really simple solution to this. Just set CMAKE_CXX_CLANG_TIDY (there is CMAKE_C_LANG_TIDY for your C code as well) and your done! At least almost. You can set CMAKE_CXX_CLANG_TIDY either in your CMakeList.txt or you can do it from the command line.

set(CMAKE_CXX_CLANG_TIDY "clang-tidy;-checks=*")

or in CMakeLists.txt

set(CMAKE_CXX_CLANG_TIDY "clang-tidy;-checks=*")

These two example above will run Clang-Tidy with all checks enabled.

Passing arguments to Clang-Tidy

The string you pass the CMAKE_CXX_CLANG_TIDY is your different arguments to Clang-Tidy. So the example above passes -checks=* to Clang-Tidy.

Getting checks on headers

By default Clang-Tidy will not check your header files for problems. But you might be interested in running Clang-Tidy on your headers as well. This is done with the argument -header-filter=.. For example:

set(CMAKE_CXX_CLANG_TIDY 
  clang-tidy;
  -header-filter=.;
  -checks=*;)

The above snippet from CMakeLists.txt will make sure to also check header in the .-folder, the project folder. You might need to change this depending on your project setup.

Treating warning as errors

A really nice feature is that you can treat warnings as errors if you like. This can be enabled at any time or maybe just on your CI-build.

The idea is that you configure a number of checks using -checks=... and you configure which of those shall be treated as errors.

Lets say we enable two (randomly selected checks), -checks=bugprone-*,cppcoreguidelines-avoid-goto. Now we set which we would like to treat as errors. If we set -warnings-as-errors=* both of the two tests above will generate errors. If you set warnings-as-errors=cppcoreguidelines-avoid-goto only the test cppcoreguidelines-avoid-goto will be treated as an error.

Remember that by setting -warnings-as-errors=...you don’t enable any test, this must be done by using -checks=.

Below is a example how -warnings-as-errors looks in CMake.

set(CMAKE_CXX_CLANG_TIDY
  clang-tidy;
  -header-filter=.;
  -checks=*;
  -warnings-as-errors=*;)

Example repo

I’ve made a simple example, with some problems that Clang-Tidy finds. You can find it at my Github repo.

Let QQmlFileSelecor select which QML file to use

One problem I've been facing now and then when developing QML is the need for selecting different QML files depending on hardware, operating system, customer brand etc. QML has a pretty unknown feature for this called QQmlFileSelecor Continue reading

Using QML:s new DelegateChooser

Published on March 01, 2019

Using ccache together with qmake and QtCreator

Published on January 30, 2019