At the present time, for R 3.6.3 and Rcpp v1.0.4 there is an issue with the CRAN binaries of Rcpp. When compiling, you may receive an error message with: In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/unistd.h:655, /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/gethostuuid.h:39:17: error: ‘uuid_t’ was not declared in this scope; did you mean ‘Rcpp::uuid_t’? 39 | int gethostuuid(uuid_t, const struct timespec *) OSX_AVAILABLE_STARTING(MAC_10_5, __IPHONE_NA); | ^~~~~~ | Rcpp::uuid_t Solution The fix is to download and install a patched …