[R-SIG-Mac] Robust compiler toolchain for R-devel

[Patrick Schratz]

Hi,

I am experimenting since some days to find the “best” compiler toolchain for R-devel to get R-devel package source installs on the new macOS Github Actions runners work in a somewhat stable way.
I am also on macOS locally which I use for testing as well.

I am aware of https://github.com/rmacoslib/r-macos-rtools. However, using clang7 for all (CC, CXX, etc) leads to some packages failing to build (sometimes due to missing OpenMP capabilities, sometimes undefined).

Therefore I decided to try out gcc (v8 and v9). While this solves most of the OpenMP issues, I am running into problems for other packages regarding CC compilation.

Turns out that using any clang version for CC solves most problems but not all.
However then I have a mix of gcc and clang which is most likely cause other issues.

Currently Jeroen is developing a new gcc8 based toolchain for Windows.

I was reading the macOS CRAN dev pages but could not find any reasoning why

• clang7 is suggested
• gcc is not used
• What future plans are there for the toolchain on macOS

Could someone shine some light on this? Thanks :)

Cheers, Patrick

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