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Cpp Language Server

You can use Cpp Language Server (cpp_ls) to get C, C++ and CUDA support:

  • no build system is required: a compile_commands.json is used for exact per-file flags when it exists, and a .cppls.toml file in the workspace root can name the language standard, the include paths and the defines;
  • completion, hover, signature help, definition, references, rename, call hierarchy, workspace symbols, inlay hints, semantic tokens, folding, selection ranges, formatting and diagnostics are provided by the server.

Install the language server

cpp_ls is distributed as one asset per OS and architecture in the GitHub releases, and the LSP4IJ template installs the right one for you.

  1. Select Cpp Language Server as the template from the available options. This will populate the command field with a default command (cpp_ls, or cpp_ls.exe on Windows), the file type mappings, the cppls settings and the installer.

  2. Install the language server from the Installer tab, by clicking the Check / Run Installation link:

    • Check Installation tests whether cpp_ls has already been installed in $USER_HOME$/.lsp4ij/lsp/cpp_ls.
    • Run Installation downloads the asset which matches your OS and architecture, extracts it in $USER_HOME$/.lsp4ij/lsp/cpp_ls, and updates the server command to the extracted executable.
    • Check / Run Installation does both, which is the simplest choice on a fresh installation.

    The assets which the installer selects are:

    OS Architecture Asset
    Windows x64 cpp_ls-win32-x64.zip
    Windows x86 cpp_ls-win32-ia32.zip
    Windows arm64 cpp_ls-win32-arm64.zip
    Linux x64 (glibc 2.17 or newer) cpp_ls-linux-x64-glibc.2.17.tar.gz
    Linux aarch64 (glibc 2.17 or newer) cpp_ls-linux-aarch64-glibc.2.17.tar.gz
    Linux riscv64 cpp_ls-linux-riscv64.tar.gz
    macOS Apple Silicon cpp_ls-darwin-arm64.tar.gz
    macOS Intel cpp_ls-darwin-x64.tar.gz

    The archives contain a single executable at their root: cpp_ls.exe on Windows, cpp_ls on Linux and macOS.

    If you prefer to install it yourself, download the asset which matches your OS and architecture, extract it, and set the command in the Server tab to the extracted executable.

    The installer selects the -glibc.2.17 assets on Linux, since they run on every distribution which provides glibc 2.17 or newer. On a musl based distribution (Alpine), download cpp_ls-linux-musl.tar.gz yourself, and set the command to the extracted cpp_ls executable.

  3. Optional: customize the Mappings tab. The template maps:

    • *.c, *.i to the c language id,
    • *.cpp, *.h, *.hpp, *.cc, *.cxx, *.inl, *.ipp, *.ixx, *.mpp, *.mxx, etc to the cpp language id,
    • *.cu, *.cuh to the cuda-cpp language id.

  4. Optional: customize the settings in the Configuration tab (Server sub-tab), see Settings below.

  5. Click OK to apply the changes. You should now have C, C++ and CUDA support enabled in your IDE, with the Cpp Language Server integrated, and you should see the language server in the LSP console.

Command

cpp_ls talks LSP over its standard input and output, so the command needs no argument:

  • cpp_ls on Linux and macOS.
  • cpp_ls.exe on Windows.

Useful options, to add to the command if needed:

  • --log-level (error, warn, info (the default), debug, trace) and --log-path (the file to log to; none, the default, disables file logging) to diagnose a problem;
  • --communication stdio (the default) and --communication tcp --port ${port} to choose how the server talks LSP. For TCP, also set Transport to Socket with Start the language server, LSP4IJ connects to it, since cpp_ls listens on the port, and Port to Auto or a port; see Transport.

LSP4IJ sends the name of the IDE as its client info, which the server recognizes for the IntelliJ based IDEs it knows; --editor intellij can be added to the command to force this mode.

Settings

The server reads its settings from the cppls section, which LSP4IJ answers from the template settings.json:

{
  "cppls": {
    "exclude": [
      "**/build/**",
      "**/third_party/**"
    ]
  }
}

cppls.exclude is the list of glob patterns of the files and folders which the server must not analyse (a build tree, a vendored copy, generated sources). An empty list means that only the server's own rules apply.

A project can also provide a .cppls.toml file at its root for the language standard, the include paths, the defines, per-path rules and the diagnostic switches, and a compile_commands.json file for the exact per-file flags. See the configuration documentation for the details.