Yes, this did the trick, thanks very much! I?m cc?ing r-devel just for the record. Roger Koenker r.koenker at ucl.ac.uk<mailto:r.koenker at ucl.ac.uk> Department of Economics, UCL London WC1H 0AX. On Aug 7, 2019, at 4:55 PM, Steven Dirkse <sdirkse at gams.com<mailto:sdirkse at gams.com>> wrote: Roger, Updating Xcode has the unfortunate side effect of wiping out the std header files from /usr/include. The fix - once you know about it - is mercifully easy. Here's my notes on the subject, recorded only yesterday so I don't waste more time the next time. Xcode 10.3 Aug 2019: we updated to Xcode 10.3. First, we did the update through the App Store. Next, we opened Xcode in the App Store and said yes to ?Install required additional components?? But that's not all! As admin, I did sudo open /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg FYI, I needed an additional step to manually patch /usr/include/sys/ucred.h but it's not likely you'll need that. -Steve On Wed, Aug 7, 2019 at 11:46 AM Koenker, Roger W <rkoenker at illinois.edu<mailto:rkoenker at illinois.edu>> wrote: Dear All, Just when I thought I had the plague of gfortran-9 under control, I made the tactical error of allowing my mac mini to ?upgrade? to macOS 10.14.6 which apparently also upgraded Xcode to 10.3. In consequence I?m having difficulty building my packages. The current symptom is: /usr/local/clang7/bin/clang -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I/usr/local/clang7/include/c++/v1 -fPIC -Wall -g -O2 -c mcmb.c -o mcmb.o In file included from mcmb.c:11: /usr/local/clang7/include/c++/v1/stdio.h:108:15: fatal error: 'stdio.h' file not found #include_next <stdio.h> ^~~~~~~~~ My first thought was I should install Simon?s clang-7.0.0 and gfortran-6.1 packages which I dutifully did. The next thought was to update my ~/.R/Makevars file to: CC=/usr/local/clang7/bin/clang CXX=/usr/local/clang7/bin/clang++ LDFLAGS=-L/usr/local/clang7/lib CPPFLAGS=-I/usr/local/clang7/include/c++/v1 FC=/usr/local/gfortran/bin/gfortran FLIBS=-L/usr/local/gfortran/lib -lgfortran Further googling has left me unenlightened? oh, and I?m running R version 3.6.1 (2019-07-05) -- "Action of the Toes" Roger Koenker r.koenker at ucl.ac.uk<mailto:r.koenker at ucl.ac.uk> Department of Economics, UCL London WC1H 0AX. ______________________________________________ R-devel at r-project.org<mailto:R-devel at r-project.org> mailing list stat.ethz.ch/mailman/listinfo/r-devel -- Steven Dirkse, Ph.D. GAMS Development Corp. office: 202.342.0180 [[alternative HTML version deleted]]