docs: Add config instructions for clangd with libvirt

In build environments which use gcc as the default compiler, use of the
clangd LSP server (for enhanced code editing and navigation etc.) with
libvirt requires some additional configuration.  Detail this and link
from `hacking.rst`.

Signed-off-by: Tim Small <tim@seoss.co.uk>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

diff --git a/docs/clangd.rst b/docs/clangd.rst
new file mode 100644 (file)
index 0000000..93570ae
--- /dev/null
+++ b/docs/clangd.rst
@@ -0,0 +1,51 @@
+=========================
+Using Clangd with Libvirt
+=========================
+
+`clangd <https://clangd.llvm.org/>`__ is an implementation of the
+`language server protocol
+<https://en.wikipedia.org/wiki/Language_Server_Protocol>`__ for C
+and C++.
+
+When paired with an LSP-compatible editor or IDE (e.g. emacs,
+vim, vscode), ``clangd`` can helpful when working with libvirt's
+C sources e.g. navigating the code base.
+
+Whilst other C LSPs are available, ``clangd`` should work
+correctly with the libvirt because clang is a supported compiler
+for libvirt, and ``clangd`` is part of the same code base as
+clang.
+
+If clang is the default compiler on your system, then ``clangd``
+can be used as soon as ``meson setup`` has been run.
+
+If gcc is your build environment's default compiler, then
+additional steps are required to use ``clangd``:
+
+``clangd`` looks for a ``compile_commands.json`` file in the top
+level directory of the project and also in the ``build/``
+subdirectory to discover which include paths, compiler flags etc.
+should be used when it parses each source file.
+
+Meson creates a ``compile_commands.json`` in the build directory.
+Meson defaults to the system's default C compiler. When the
+default compiler is gcc, its ``compile_commands.json`` output
+cannot be used with ``clangd`` due to differences in compiler
+invocation flags when building libvirt.
+
+Create a separate build directory with a ``clangd`` compatible
+``compile_commands.json`` as follows:
+
+::
+
+   CC=clang CXX=clang++ meson setup build-clang
+
+Point ``clangd`` (v12 or later) at the correct
+``compile_commands.json`` by placing the following into a
+``.clangd`` file in the root of the project:
+
+::
+
+   ---
+   CompileFlags:
+     CompilationDatabase: "build-clang"

diff --git a/docs/hacking.rst b/docs/hacking.rst
index a04da9cb583ead2f166ae507d72f891f34d0f176..11cd21223ad8bd8d122027cbb23506a9fd6f1adb 100644 (file)
--- a/docs/hacking.rst
+++ b/docs/hacking.rst
@@ -28,6 +28,9 @@ The `"Git checkout" section <compiling.html#git-checkout>`__
 of the libvirt installation instructions give an overview of the
 compilation process.
 
+Optionally, `Clangd with libvirt <clangd.html>`__ can be used to
+navigate the code base etc. within most code editors (and IDEs).
+
 Preparing patches
 =================
 

diff --git a/docs/meson.build b/docs/meson.build
index 201fd4c984aeef8d5a117f7aa0b39b47d6865453..70d271ec6ee903d54d14a6dc0e0949197232ff9a 100644 (file)
--- a/docs/meson.build
+++ b/docs/meson.build
@@ -32,6 +32,7 @@ docs_rst_files = [
   'ci',
   'ci-dashboard',
   'ci-runners',
+  'clangd',
   'coding-style',
   'committer-guidelines',
   'compiling',