These have been undocumented for years, and are now deprecated (as they
pollute the namespace), so please remove at your next update. It may be
convenient to copy these into your package:
typedef double Sfloat;
typedef int Sint;
It is planned that this will be checked on CRAN incoming soon and become
an error in R 4.3.0 next Spring.
You can check this in current R-devel by defining NO_S_TYPEDEFS before
including <R.h>.