Low-level R library bindings

The recommended way to build this library is to use precompiled bindings, which are available for Linux, macOS, and Windows.

Alternatively, the library can be built from source, in which case it invokes bindgen crate, which has extra platform-specific dependencies (including msys2 for Windows).

libR-sys recognizes the following environment variables:

• LIBRSYS_R_VERSION If set, it is used to determine the version of R, for which bindings should be generated. LIBRSYS_R_VERSION should be set to one of the supported values, e.g. 4.2.0 or 4.3.0-devel (the pattern is major.minor.patch[-devel]). Malformed LIBRSYS_R_VERSION results in compilation error. If LIBRSYS_R_VERSION is unset, R is invoked and its R.version is used.

Two components are required to build the library:

1. R: It needs to be installed and available in the search path.
2. Rust: It is recommended to install Rust using rustup; search path should include Rust binaries.

Note: On Windows, only R >= 4.2 is supported

Once R and Rust are configured, the library can be easily built:

# macOS & Linux
cargo build

# Windows
cargo build --target x86_64-pc-windows-gnu

To test the build, run cargo test.

# macOS & Linux
cargo test

# Windows
cargo test --target x86_64-pc-windows-gnu

Note: On Windows, only R >= 4.2 is supported

The bindings can be generated using bindgen, special Rust crate. bindgen usage is enabled via use-bindgen feature flag.

bindgen requires libclang, which should be installed first. This library relies on LIBCLANG_PATH environment variable to determine path to the appropriate version of libclang.

The output folder for bindings can be configured using LIBRSYS_BINDINGS_OUTPUT_PATH environment variable, thus make sure it is set to e.g bindings.

• Linux

  Set LIBCLANG_PATH to the lib directory of your llvm installation, e.g., LIBCLANG_PATH=/usr/lib/llvm-3.9/lib. Build & test using

  cargo build --features use-bindgen
  cargo test  --features use-bindgen 

• macOS

  Install llvm-config via homebrew with:

  brew install llvm

  Add it to your search path via:

  echo 'export PATH="/usr/local/opt/llvm/bin:$PATH"' >> ~/.bash_profile

  If you want to compile libR-sys from within RStudio, you may also have to add the following line to your .Renviron file:

  PATH=/usr/local/opt/llvm/bin:$PATH

  Build & test using

  cargo build --features use-bindgen
  cargo test  --features use-bindgen 

• Windows On Windows, bindings can be generated using native LLVM installation and Rtools distribution.

  Install LLVM:

  choco install llvm -y

  LLVM can be also installed using winget, scoop, or manually.

  To ensure LLVM is successfully installed and configured, run clang --version. If clang is not on the PATH, manually add path to clang installation to the PATH environement variable.

  Install Rtools if it is misisng:

  choco install rtools -y

  Installing Rtools this way automatically sets RTOOLS42_HOME (or RTOOLS43_HOME) environment variable.

  Ensure that R_HOME environment variable is set to the R installation directory.

  Finally, point libR-sys to the include directory of Rtools:

  $env:LIBRSYS_LIBCLANG_INCLUDE_PATH="$env:RTOOLS42_HOME\x86_64-w64-mingw32.static.posix\include"

  Now, the bindings can be build using the following command:

  cargo build --target x86_64-pc-windows-gnu --features use-bindgen

Running bindgen tests on Windows requires a bit more setup.

First, add Rtools bin directory to the PATH (replace RTOOLS42_HOME with RTOOLS43_HOME if you are using Rtools 4.3):

$env:PATH  = ";$env:RTOOLS42_HOME\x86_64-w64-mingw32.static.posix\bin"

Second, patch Rtools version 4.2 and higher since there is a gcc static linking issue. rustc adds -lgcc_eh flag to the compiler, but Rtools' GCC doesn't have libgcc_eh due to the compilation settings. So, in order to please the compiler, libgcc_eh should be mocked and added to the library search paths. For more details, please refer to r-windows/rtools-packages.

Create a directory for missing library file and an empty file there:

# create a directory in an arbitrary location (e.g. libgcc_mock)
New-Item -Path libgcc_mock -Type Directory

# create empty libgcc_eh.a and libgcc_s.a
New-Item -Path libgcc_mock\libgcc_eh.a -Type File

Finally, configure Rust compiler and select appropriate linker (see The Cargo Book):

$env:CARGO_TARGET_X86_64_PC_WINDOWS_GNU_LINKER="x86_64-w64-mingw32.static.posix-gcc.exe"
$env:LIBRARY_PATH="libgcc_mock" # Replace it with the path to the directory created above

Alternatively, linker can be configured in .cargo/config.toml:

[target.x86_64-pc-windows-gnu]
linker = "x86_64-w64-mingw32.static.posix-gcc.exe"

Now, the tests can be run:

cargo test --target x86_64-pc-windows-gnu --features use-bindgen

{
    // The target needs to be GNU
    "rust-analyzer.cargo.target": "x86_64-pc-windows-gnu",
    // Specify "use-bindgen" for developing R-devel.
    "rust-analyzer.cargo.features": [],
    "terminal.integrated.env.windows": {
        "R_HOME": "C:/Program Files/R/R-4.2.2",
        "PATH": "${env:R_HOME}/bin/x64;C:/rtools42/x86_64-w64-mingw32.static.posix/bin;C:/rtools42/usr/bin;${env:PATH}"
    }
}