[Rd] Registration of native routines

[Prof Brian Ripley]

Registration of 'native routines' (entry points in compiled code loaded 
into R) has been available for over 14 years, but few packages make use 
of it (less than 10% of those on CRAN with compiled code).

Registration has similar benefits to name spaces in R code:

- it ensures that the routines used by .C, .Call etc are those in your 
package (without needing a PACKAGE argument).

- it avoids polluting the search space for native routines with those 
from your package.

- it checks the number of arguments passed to .Call/.External, and the 
number and optionally the type for .C/.Fortran.

- it finds native routines faster, especially if 10s of name spaces are 
loaded.

Kurt Hornik and I have written a tool to make adding registration much 
easier.  From NEWS in R-devel

     • Package tools has a new function
       package_native_routine_registration_skeleton() to assist adding
       native-routine registration to a package.  See its help and §5.4.1
       of ‘Writing R Extensions’ for how to use it.  (At the time it was
       added it successfully automated adding registration to over 90%
       of CRAN packages which lacked it.  Many of the failures were
       newly-detected bugs in the packages, e.g. 50 packages called
       entry points with varying numbers of arguments and 65 packages
       called entry points not in the package.)

Of the 2450 CRAN packages with compiled code but not registration, this 
tool successfully[*] converts all but 220 out-of-the-box.  Another 25 
packages already use R_init_pkgname and so need the registration info to 
be merged.

Most of the rest fail because of errors in the package but some try to 
do tricky things computing names of routines, and this is noted in the 
skeleton output.

A few of you are using the older mechanism of specifying entry points in 
a useDynLib call in the NAMESPACE file. This shares the first and fourth 
benefits (but registration is faster), but not the second and third.

$5.4 of the 'Writing R Extensions' manual has been re-written with a 
worked example of adding registration.

Shortly, R CMD check --as-cran will note if registration is not fully 
used.  Expect to be asked to add registration: as increasingly large 
numbers of packages are used, avoiding polluting the search space is 
becoming important.

(There are reports that the check in 'R CMD check' on Windows sometimes 
fails to detect use of registration.  This is being looked into: 
meanwhile say so in a CRAN submission if it happens to you.)


[*] R CMD check output is unchanged.

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