CLion Dev

CLion is an IDE

Prerequisite: Checking out and building the chromium code base

Setting up CLion

Install CLion
- Googlers only: See go/intellij-getting-started for installation and license authentication instructions
Run CLion
Increase CLion's memory allocation
This step will help performance with large projects
1. Option 1
  1. At the startup dialog, in the bottom left corner, click on the Cog icon and then click on Edit Custom VM Options:
  2. In the textbox, you will see different flags. Add or replace the following flags (to learn more: Advanced configuration | IntelliJ IDEA):
```
-Xss2m
-Xms1g
-Xmx31g
...
```
  3. Close the Edit Custom VM Options dialog.
  4. Again, at the startup dialogue, in the bottom left corner, click on the Cog icon and then click on Edit Custom Properties:
  5. Add or replace the following flags (to learn more: Platform Properties | IntelliJ IDEA):
```
idea.max.intellisense.filesize=12500
```
2. Option 2; 2017 and prior versions may not include the options to setup your VM Options and Properties in the configure menu. Instead:
  1. Create New Project
  2. Help > Edit Custom VM Options
  3. Help > Edit Custom Properties

Creating a new CLion project

Import project
- At the startup dialog, select Import Project and select your chromium directory; this should be the parent directory to src. Selecting src instead would result in some CLion IDE files appearing in your repository.

Building, Running, and Debugging within CLion

Configure CLion to use ninja for building (see Linux Build Instructions)

Custom Build Targets

A custom Build Target allows CLion to compile Chromium similarly to running ninja in the command line.

Add a Custom Build Target

The first step is to add Ninja (specifically autoninja) as an external tool that will be used to create the build targets.

Go to Settings
Then, to Build, Execution, Deployment > Custom Build Targets
Click on the + sign to add a new build target.
Fill the Name: Default
Next to Build, click on the three dots (...)
Click on + to add an External Tool
Fill the form:
1. Name: autoninja - Default
2. Program: <absolute path to depot_tools/autoninja>
3. Arguments: -C out/Default chrome
4. Working Directory: <absolute path to chromium/src>
Click Ok to close the dialog.

Run/Debug configuration

The build target configured in the previous section was necessary to configure the Run/Debug configuration.

Click on the Run menu and then on Edit Configurations.
Click on the + sign then on Custom Build Application
Fill the form:
1. Name: Default
2. Target: Select the Default build target that was created previously.
3. Executable: Click the three dots (...) and select src/out/Default/chrome
Click Ok to close the dialog.

Configure `~/.gdbinit`

Before being able to debug, you need to configure ~/.gdbinit. Open it with a text editor and enter:

source <path to chromium>/src/tools/gdb/gdbinit

Set the local gdb executable

There have been some reports of slowness while debugging using CLion. It seems that using that CLion's bundled gdb executable is the culprit. To use the local one:

Open Settings
Search for Toolchains
Next to Debugger, select /usr/bin/gdb

Run Chrome!

You can now run chrome directly from CLion. You can also debug and add a breakpoint. Try it!

Run > Run (shift+f10) or Run > Debug (shift+f9) (screenshot) debugging screenshot

Autocompletion

Approach 1: Using CMakeLists

Note: It's possible that when you open the project, CLion created one for you.

Create or Modify the chromium/CMakeLists.txt file

Open chromium/CMakeLists.txt

Add or Replace the content with:

cmake_minimum_required(VERSION 3.10)
project(chromium)

set(CMAKE_CXX_STANDARD 14)

include_directories(${CMAKE_CURRENT_SOURCE_DIR}/src)
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/src/out/Default/gen)
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/src/third_party/protobuf/src)
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/src/third_party/googletest/src/googletest/include)
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/src/third_party/googletest/src/googlemock/include)
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/src/third_party/abseil-cpp)

# The following file used is irrelevant, it's only to improve CLion
# performance. Leaving at least 1 file is required in order for CLion
# to provide code completion, navigation, etc.
add_executable(chromium src/components/omnibox/browser/document_provider.cc)

Approach 2: Compilation database

Since Chromium does not use CMake to build, to “benefit from the advanced IDE features that CLion provides”, a Compilation database must be created to expose to CLion how Chromium is built.

In the Chromium code source, there’s a python script src/tools/clang/scripts/generate_compdb.py that will generate the Compilation Database.

Note: The two approaches are not currently compatible and switching between one and the other is cumbersome. To go from approach 1 to 2, the CMakeWorkspace line from .idea/misc.xml must be removed first.

Run from your chromium folder:

python3 src/tools/clang/scripts/generate_compdb.py -p src/out/Default -o ./compile_commands.json --target_os=linux

This generates the compilation database at chromium/compile_commands.json.

In CLion, select the compile_commands.json file in the project navigator, right-click on it, then click on Load Compilation Database Project.
Note: This step will produce a few hundred errors but it doesn‘t cause any issues. It’s simply because some files are not compiled. To remove some errors, these flags can be added in src/out/Default/args.gn:
```
enable_nocompile_tests=true
```
CLion will start processing the files and will start indexing the symbols. This step can take a few hours. To expedite this process, see the section Exclude irrelevant folders from indexing to speed up CLion below.

Optional Steps

Create terminal cli or desktop entry

To make it easier to startup CLion or open individual files:

Open the actions menu (ctrl+shift+a)
Type create desktop entry and press enter
Open the actions menu and enter create command-line launcher

Exclude irrelevant folders from indexing to speed up CLion

Exclude folders that are irrelevant to your work from the indexing. Exclude at first the following folders and manually include the ones relevant to you. Open chromium/.idea/misc.xml and under <project> add or edit the following XML component:

Note: This step can be done from the UI in the Project view by selecting all the folders to exclude, right-clicking on them, selecting Mark Directory As and then selecting Excluded.

<component name="CidrRootsConfiguration">
    <excludeRoots>
      <file path="$PROJECT_DIR$/src/android_webview" />
      <file path="$PROJECT_DIR$/src/apps" />
      <file path="$PROJECT_DIR$/src/ash" />
      <file path="$PROJECT_DIR$/src/build" />
      <file path="$PROJECT_DIR$/src/build_overrides" />
      <file path="$PROJECT_DIR$/src/buildtools" />
      <file path="$PROJECT_DIR$/src/cc" />
      <file path="$PROJECT_DIR$/src/chromecast" />
      <file path="$PROJECT_DIR$/src/chromeos" />
      <file path="$PROJECT_DIR$/src/codelabs" />
      <file path="$PROJECT_DIR$/src/content" />
      <file path="$PROJECT_DIR$/src/courgette" />
      <file path="$PROJECT_DIR$/src/crypto" />
      <file path="$PROJECT_DIR$/src/dbus" />
      <file path="$PROJECT_DIR$/src/device" />
      <file path="$PROJECT_DIR$/src/docs" />
      <file path="$PROJECT_DIR$/src/extensions" />
      <file path="$PROJECT_DIR$/src/fuchsia_web" />
      <file path="$PROJECT_DIR$/src/gin" />
      <file path="$PROJECT_DIR$/src/google_apis" />
      <file path="$PROJECT_DIR$/src/google_update" />
      <file path="$PROJECT_DIR$/src/gpu" />
      <file path="$PROJECT_DIR$/src/headless" />
      <file path="$PROJECT_DIR$/src/infra" />
      <file path="$PROJECT_DIR$/src/ios" />
      <file path="$PROJECT_DIR$/src/ipc" />
      <file path="$PROJECT_DIR$/src/media" />
      <file path="$PROJECT_DIR$/src/mojo" />
      <file path="$PROJECT_DIR$/src/native_client" />
      <file path="$PROJECT_DIR$/src/native_client_sdk" />
      <file path="$PROJECT_DIR$/src/net" />
      <file path="$PROJECT_DIR$/src/out" />
      <file path="$PROJECT_DIR$/src/pdf" />
      <file path="$PROJECT_DIR$/src/ppapi" />
      <file path="$PROJECT_DIR$/src/printing" />
      <file path="$PROJECT_DIR$/src/remoting" />
      <file path="$PROJECT_DIR$/src/rlz" />
      <file path="$PROJECT_DIR$/src/sandbox" />
      <file path="$PROJECT_DIR$/src/services" />
      <file path="$PROJECT_DIR$/src/skia" />
      <file path="$PROJECT_DIR$/src/sql" />
      <file path="$PROJECT_DIR$/src/storage" />
      <file path="$PROJECT_DIR$/src/styleguide" />
      <file path="$PROJECT_DIR$/src/testing" />
      <file path="$PROJECT_DIR$/src/third_party" />
      <file path="$PROJECT_DIR$/src/tools" />
      <file path="$PROJECT_DIR$/src/ui" />
      <file path="$PROJECT_DIR$/src/url" />
      <file path="$PROJECT_DIR$/src/v8" />
      <file path="$PROJECT_DIR$/src/venv" />
      <file path="$PROJECT_DIR$/src/weblayer" />
    </excludeRoots>
  </component>

Mark directories as `Library Files`

To speed up CLion, optionally mark directories such as src/third_party as Library Files

Open the Project navigation (alt+1)
Select and right-click the directories > Mark directory as > Library Files
See https://blog.jetbrains.com/clion/2015/12/mark-dir-as/ for more details