[R-SIG-Mac] R CMD check warning in 4.0.0 RC

[Prof Brian Ripley]

On 20/04/2020 16:51, Duncan Murdoch wrote:
> I've just installed R version 4.0.0 RC (2020-04-18 r78249) and am 
> checking a package on MacOS High Sierra (10.13.6).  I can't install the 
> recommended version of Xcode on this MacOS version.  I'm currently using 
> Xcode 9.2.  (I think Xcode 10.x is supposed to work on High Sierra, but 
> it isn't obvious how to update.)
> 
> My package has a small amount of C code, and R CMD check is clean, but R 
> CMD check --as-cran gives this NOTE:
> 
> * checking compilation flags used ... NOTE
> Compilation used the following non-portable flag(s):
>    ‘-mmacosx-version-min=10.13’
> 
> I didn't supply that, it's the default, so probably this note should not 
> appear (even though the message is true).

The customizations for R CMD check are in the 'R Internals' manual. 
That would have shown that you needed

setenv _R_CHECK_COMPILATION_FLAGS_KNOWN_ "-mmacosx-version-min=10.13"

It is too late for 4.0.0 but in any case I would be reluctant to include 
that in the 'known good' flags.  What is not at all clear is which 
compilers support it (even on macOS) -- it seems to be in the LLVM 
version of clang but undocumented (like so many clang flags).

-- 
Brian D. Ripley,                  ripley using stats.ox.ac.uk
Emeritus Professor of Applied Statistics, University of Oxford