README: Document compile_commands.json.

README.md

@@ -219,6 +219,42 @@ script `wine/tools/gdbinit.py` (source it) that provides `load-symbol-files`
 (or `lsf` for short) command which loads the symbols for all the mapped files.
 
 
+`compile_commands.json`
+-----------------------
+
+For use with [clangd](https://clangd.llvm.org/) LSP server and similar tooling.
+
+Projects built using cmake or meson (e.g. vkd3d-proton) automatically come with
+`compile_commands.json`. For autotools (e.g. wine) you have to [configure the
+build](#configuring-the-build) with `--enable-bear` that uses
+[bear](https://github.com/rizsotto/Bear) to create the compilation database.
+It's not on by default as it make the build slightly slower.
+
+The build system collects all the created compile_commands.json files in a
+build subdirectory named `compile_commands/`.
+
+The paths are translated to point to the real source (i.e. not the rsynced
+copy). It still may depend on build directory for things like auto-generated
+`config.h` though and for wine it may be beneficial to run `tools/make_requests`
+in you source directories as those changes are not committed.
+
+You can then configure your editor to use that file for clangd in a few ways:
+
+1) directly - some editors/plugins allow you to specify the path to `compile_commands.json`
+2) via `.clangd` file, e.g.
+```bash
+cd src/proton/wine/
+cat > .clangd <<EOF
+CompileFlags:
+  CompilationDatabase: ../build/current-dev/compile_commands/wine64/
+EOF
+```
+3) by symlinking:
+```bash
+ln -s ../build/current-dev/compile_commands/wine64/compile_commands.json .
+```
+
+
 Runtime Config Options
 ----------------------