[R-SIG-Mac] Experiences with macOS Sierra

[Prof Brian Ripley]

So far I have encountered few problems.  R.app runs but I do not 
normally use it so my tests were minimal.

My observations are about installing packages from source.

- It seems Apple has been tidying up, and I had ca 20GB more free space 
after upgrading (which is worthwhile on my MBA with a 128GB SSD).  It 
seems that includes removing some headers, including those for openssl 
(used by packages PKI and RSclient - package opensssl uses its own). 
This is but the latest instance in a long-term trend, e.g. iodbc, pcre 
and liblzma have libraries but no headers.

- Finally the POSIX 2008 function clock_gettime is supported (and will 
be used by R): but package scrypt calls it incorrectly.

Xcode 8 is available for EL Capitan but I would caution against using it 
there (despite it being pushed as an update from the AppStore).  AFAICS 
(and googling will find other reports) it defaults to the macOS 10.12 
SDK and that declares functions such as clock_gettime not available in 
El Capitan.  (I believe that R checks thoroughly enough not to be caught 
by this.)

There is a further problem with Xcode 8, also seen on Sierra.  Packages 
using xml2-config (such as XML) fail to install.  Apple modified 
xml2-config to look on the SDK path, which means packages using it 
attempt to link to .tbd files rather than .dylibs.  Which should be OK 
but the supplied .tbd attempt to link to libraries removed in Sierra and 
so linking fails. (This is not a problem with the version 8 of the 
Command Line Tools, only available for Sierra.)

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