compdb

Many modern C++ development tools in the clang/LLVM toolchain, such as clang-tidy or clangd, rely on the presence of a compilation database in JSON format. This package temporarily injects additional build flags into the R build process to generate such a compilation database.

Caveats

1. A full package build including compilation is necessary to generate the compilation database.

2. This package is purely meant for platforms that support R built with clang, which essentially excludes Windows. Rtools is built around GCC and I am not aware of clang being used within the R world on Windows.

3. Currently, this method only works for packages utilizing the standard R build process, i.e. the only modifications to the build process come in the form of Makevars, or the configurable variant Makevars.in, in the package’s src directory. This supports a broad range of packages since it allows for custom configure files as long as they do not create a Makevars file from scratch but rather modify a Makevars.in.

   For packages using their own custom Makefiles, additional effort from the package authors side may be necessary to generate the compilation database(s).

Installation

You can install the development version of compdb like so:

remotes::install_github("cyianor/r-compdb")

You can install the current stable version of compdb from CRAN like so:

install.packages("compdb")

Example

Using this package is simple and only requires a call to

build_compile_commands(path = ".")

where path should point to the packages base path. It will produce a file called compile_commands.json in the package’s src/ directory.

How it works

The package at path is built as a source package to a temporary location. If the package already contains a Makevars file, it is modified at the temporary location to include PKG_CPPFLAGS += -MJ \@.json which will prompt clang to generate a compilation database for each file it processes. If no Makevars file exists, a new one is created. The package is then installed to a temporary location which triggers compilation of all source files and thereby generates the compilation databases.

Finally, the compilation databases are merged and the directory of each file in the compilation database is corrected from the temporary directory to the actual package directory.

Inspiration

This package is essentially a re-implementation of the bash script at ashiklom/rcpp-cmpdb with additional bells and whistles.