How to Develop C/C++ with VSCode and Clangd

TL;DR

  1. Install VSCode plugin clangd
  2. Install clangd in source code environment
    • (Local) install clangd locally
    • (Docker) install clangd inside the Docker container
    • (Remote) install clangd on the remote server
  3. Adding flag -DCMAKE_EXPORT_COMPILE_COMMANDS=1 to CMake command and rerun cmake
  4. (Optional) Run VSCode command clangd: Restart language server

Explained

Modern code editors uses LSP (Language Server Protocol) to provide consistent features (e.g. code completion, go-to-definition, and refactoring). LSP architecture is shown below, using clangd as an example.

clangd LSP architecture

LSP client handles editor commands and queries the server. The LSP server parses the source code and provides the results back to the client. Then the LSP client displays the results to the user.

clangd is a language server for C/C++, based on the Clang compiler. Since source files are not self-contained in C++, clangd requires compile_commands.json containing compile commands for every source file in a project. This file can be generated by CMake with -DCMAKE_EXPORT_COMPILE_COMMANDS=1 flag.

Defaultly clangd uses build/compile_commands.json, but you can specify the path in .clangd configuration file. The following example of .clangd indicates clangd to use build/clangd/complie_commands.json:

CompileFlags:
  CompilationDatabase: build/clangd