How to Build the Latest Version of clangd

I'm leaving these notes here so I don't forget them.

Environment

• Ubuntu 22.04

References

Although this renders this article redundant, everything you need is documented here:

https://llvm.org/docs/CMake.html

Downloading the latest clangd

Download or git clone the entire LLVM project. As of this writing, v19 appears to be the latest version.

https://github.com/llvm/llvm-project/tree/main

I downloaded it to Downloads. Note that it's over 200MB, so ensure you have sufficient disk space.

Once downloaded, move into the directory.

~/Downloads
$ cd ./llvm-project-main

Preparation for building

This guide assumes you already have cmake installed.
On Ubuntu, you can install it using sudo apt install cmake.

1. Create a build directory

Create a directory for the build and move into it.
You can name the build directory anything you like, but here we will call it build.

~/Downloads/llvm-project-main
$ mkdir ./build
$ cd ./build

2. CMake configuration

Run the following command inside build to start the CMake configuration.

$ cmake ../llvm/ \
    -DCMAKE_BUILD_TYPE=Release \
    -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra" \

The options are explained below.

• -DCMAKE_BUILD_TYPE
  Specifies the build type. There are four types; I selected Release here.

Build Type	Optimizations	Debug Info	Assertions	Best suited for
Release	For Speed	No	No	Users of LLVM and Clang
Debug	None	Yes	Yes	Developers of LLVM
RelWithDebInfo	For Speed	Yes	No	Users that also need Debug
MinSizeRel	For Size	No	No	When disk space matters

Source
https://llvm.org/docs/CMake.html#frequently-used-cmake-variables

• -DLLVM_ENABLE_PROJECTS
  LLVM contains various projects, so specify which ones you want to build.
  In this case, we use clang and clangd. Separate them with a ;.

3. Building

Run the following command inside the build directory.

~/Downloads/llvm-project-main/build
$ cmake --build . --target install

It took about 3 to 4 hours for me, perhaps because my PC isn't very powerful. Let's wait patiently.

4. Installation

Once the build is finished, you should find the clang and clangd executables in build/bin. Once you confirm these files exist, run the following command:

~/Downloads/llvm-project-main/build
$ cmake -DCMAKE_INSTALL_PREFIX=/opt/llvm -P cmake_install.cmake

Specify the installation destination in -DCMAKE_INSTALL_PREFIX. I have a habit of placing individually source-built items in /opt, so I chose /opt/llvm.

5. Adding to PATH

It is convenient to add this to your .bash_profile.

export PATH="/opt/llvm/bin:$PATH"

6. Verifying operation with vim-lsp

Since I am using vim-lsp-settings, I add the following to my .vimrc:

let g:lsp_settings = {
            \ 'clangd': {
            \   'cmd': ['/opt/llvm/clangd-15', '--enable-config'],
            \ }
            \}

Launch Vim and check if it works properly.