Setting up include-what-you-need (IWYU)

Use following instructions to install IWYU (https://include-what-you-use.org/) on Ubuntu 18.04.3 LTS:

sudo apt-get update
sudo apt-get install -y build-essential cmake git zlib1g-dev libncurses5-dev llvm-6.0-dev libclang-6.0-dev libclang-6.0-dev clang-6.0
git clone https://github.com/include-what-you-use/include-what-you-use.git iwyu.git
cd iwyu.git
git checkout clang_6.0
mkdir -p build
cd build
cmake -DIWYU_LLVM_ROOT_PATH=/usr/lib/llvm-6.0 ..
make 
make install

Once installation is complete, you will find `include-what-you-need`

# include-what-you-use --version
include-what-you-use 0.10 (git:a1878c4) based on clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)

To execute include-what-you-need:

Build your cpp project with cmake and pass on an extra parameter `-DCMAKE_EXPORT_COMPILE_COMMANDS=TRUE` to cmake. It will produceĀ  `compile_commands.json` file in your build folder for the project.

  • Execute `iwyu_tool.py -p </path/to/folder/having/compile_command.json>`. It may take time depending upon the code size.
  • `fix_includes` can be used to apply recommended changes.

To use it in VSCode add following to the `tasks.json`

{
    "label": "CXX Analysis -- iwyu",
    "detail": "Run IWYU tool for CPP project",
    "command": "iwyu_tool.py",
    "args": [
        "-p",
        "${workspaceRoot}/build"
    ],
    "presentation": {
        "echo": true,
        "reveal": "always",
        "focus": true,
        "panel": "shared",
        "showReuseMessage": true,
        "clear": false
    },
    "problemMatcher": "$gcc"
}

Ref: https://gist.github.com/aakbar5/268a2072138345893b7f82590dcc3d26

VisualStudio code & compile_commands.json

If you are working with C/C++ in VSCode, you will find that VSCode keeps on showing

"${workspaceFolder}/build/compile_commands.json" could not be found. 'includePath' from c_cpp_properties.json will be used instead.

This message is generated by vscode-cpptools. Although it is an optional file however vscode-cpptools keeps on showing error message that it is missing.

This message can easily be fixed if you are using CMake. To do so simply add following to your CMake configuration file.

# Generate compile_commands.json
set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

Thread Module in c++11

C++11 supports Thread library (http://en.cppreference.com/w/cpp/thread). If you are using it in your application you have to pass -pthread to g++ linker to inform it which sort of backend should be used for linking Thread library. If -pthread is not passed your application will end up with following execution error:

terminate called after throwing an instance of 'std::system_error'
 what(): Enable multithreading to use std::thread: Operation not permitted
Aborted (core dumped)