[Rd] Use of R and Rscript in configure/Makevars in packages

[Prof Brian Ripley]

We have seen problems with a number of packages which use R/Rscript to 
run R code in configure or makefiles.

(a) You must give a full path: there need be no version of R in the 
path, and if there is it might not be the version/build of R under 
which package installation is being done.  So the general form is to 
use

${R_HOME}/bin/R

to select the right version.  And since ${R_HOME} might contain 
spaces, you need something like "${R_HOME}/bin/R".

There appear to be bare uses of Rscript in Rcpp RQuantLib bifactorial 
mvabund, of bare R in ROracle pgfSweave rcom and many more packages 
without quotes.

(b) There are further issues with platforms which use 
sub-architectures (mainly Mac OS X and R-devel Windows).  On Windows 
the architecture-dependent executables will (as from R 2.12.0) be in 
subdirectories of ${R_HOME}/bin, so the general form is to use one of

"${R_HOME}/bin${R_ARCH_BIN}/Rscript.exe"
"${R_HOME}/bin${R_ARCH_BIN}/Rterm.exe"
"${R_HOME}/bin${R_ARCH_BIN}/Rcmd.exe"

On R-devel Windows ${R_HOME}/bin/R.exe and ${R_HOME}/bin/Rscript.exe 
do exist and are 32-bit executables whose sole task is to launch the
appropriate executable from a sub-directory.  Since process creation 
is expensive on Windows, this intermediate step is best avoided.

On Mac OS X, ${R_HOME}/bin/R is a script that launches the 
architecture-dependent executables from a subdirectory, and on CRAN 
builds ${R_HOME}/bin/Rscript is a 'fat' (multi-arch) executable, so 
the issues have been worked around (but not necessarily for user 
installs).

(c) Calling R in configure.win will typically call 32-bit R with 
R-devel Windows.  If the result needs to depend on the architecture 
(and e.g. the library dirs may well) then the work needs to be done in 
src/Makevars.win: see the R-devel 'Writing R Extensions' manual for 
how to achieve this.

(The reason is that configure.win is called once, and then 
src/Makevars.win is called for each architecture.)

BDR

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595