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fopenmp option of clang error

When I try to source a Rcpp file, I got the following error under macOS:

clang: error: unsupported option '-fopenmp'

After a little bit Googling, I found this post, which at the end solved my problem. Briefly, I did the following steps:

  1. Installed xcode from Apple Store (a simplified version may be enough) or in Terminal withxcode-select --install
  2. Installed llvm via brew install llvm
  3. Downloaded and installed the gfortran binary installer from here. Note: You will need to download the OS X El Capitan gfortran 6.1 binaries regardless of whether or not you are on macOS Sierra, which presently only offers gfortran 6.3.
  4. Downloaded and extracted clang to /usr/local/clang (overwrite it if already exists, sudo cp -r ~/Downloads/usr/local/clang4 /usr/local/clang4). See here for more information.
  5. In terminal
   cat <<- EOF > ~/.R/Makevars
   # The following statements are required to use the clang4 binary
   # End clang4 inclusion statements

Then, the error is fixed (for now)!