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clangd

clangd is an implementation of the language server protocol (LSP) for C/C++. It can be integrated into various IDEs to provide the following functionality:

  • Code completion
  • Inlay compiler errors and warnings, with auto fix
  • Inlay clang-tidy warnings and notes, with auto fix
  • Finding unused includes
  • Go to definition and references
  • Basic refactoring, like rename symbol across files

Setup

A compile_commands.json needs to be in a place where clangd can find it. The simplest way is to make a symbolic link in the source folder.

cd <build_folder>
cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DWITH_UNITY_BUILD=OFF .
mkdir ../blender/build
cmake -E create_symlink compile_commands.json ../blender/build/compile_commands.json

The next steps depend on your IDE, for example.

  • Visual Studio Code has a clangd extension that can be installed.
  • Neovim has native lsp support, with plugins that help integrate clangd better.
  • CLion has native support.

Clang-Tidy

Besides compiler errors and warnings, more opinionated warnings and notes are provided by clang-tidy. These can help improve readability and prevent bugs.

See .clang-tidy in the root Blender source directory for the checks that are enabled.

Unused Includes

clangd also detects unused includes, see its documentation for details.

Platform differences and build options can lead to false positives. So be sure to test any changes on the Buildbot.

There are a few ways to resolve such warnings:

  • Add the relevant #ifdef around the #include for platform or build options.
  • Replace the #include by a more specific one.
  • For headers that intentionally export symbols from another header, add // IWYU pragma: export after the #include whose symbols are meant to be exported.
  • If all else fails, // IWYU pragma: keep will suppress the warning.

Limitations

clangd parses the code with full compiler flags, which gives it accurate type information. However it also means that any code not compiled may show errors or get missed by refactoring tools. Enabling full build options gives best results. For platform specific code there is no solution though.

Demo