Generate compilation databases for Rcpp packages

A simple shell script for generating compile_commands.json files for clangd and other C++ LSP servers for R packages using C code.

NOTE: This currently only works with the clang compiler (>5.1). You will need a different solution for gcc and other compilers.

Installation

Download the rcpp-compdb script into a location on your $PATH.

Usage

rcpp-cmpdb <path>

<path> defaults to the current R package directory.

How it works

1. Copy Makevars to a temporary file.
2. Add a line like PKG_CPPFLAGS += -MJ <tempdir>/$@.json to have clang create individual compilation databases for each target as part of the R package build.
3. Build the R package in a temporary folder. While compiling, it will generate compilation databases for every C++ file.
4. Combine all the individual compilation database files into a single file: <path>/src/compilation_commands.json
5. Remove all temporary directories, and restore the original Makevars file.

Helpful links

• https://github.com/cquery-project/cquery/wiki/Compilation-database
• https://sarcasm.github.io/notes/dev/compilation-database.html
• https://clang.llvm.org/docs/JSONCompilationDatabase.html
• https://clang.llvm.org/extra/clangd/Installation.html#compile-flags-txt