This blog is updated daily.
A general description is here.
‘xtabs()’ works more consistently with ‘NA’s, also in its result no longer setting them to ‘0’. Further, a new logical option ‘addNA’ allows to count ‘NA’s where appropriate. Additionally, for the case ‘sparse = TRUE’, the result's ‘dimnames’ are identical to the default case's.
Package ‘tools’ has a new function ‘package_native_routine_registration_skeleton()’ to asssist adding native-symbol registration to a package. See its help and §5.4.1 of ‘Writing R Extensions’ for how to use it.