[Rd] Detecting compilation under R
Prof Brian Ripley
ripley at stats.ox.ac.uk
Thu Dec 14 17:27:09 CET 2006
On Thu, 14 Dec 2006, Barry Rowlingson wrote:
> The docs tell me:
> "The header files define USING_R, which should be used to test if the
> code is indeed being used with R."
> but surely you only get that if you #include <R.h>, which you can only
Nope, also if you include <S.h>, which you can do under either R or
You got this from the API section in 'Writing R Extensions', and are
quoting out of context.
> do if you are using R. If you have code that you might want to compile
> in R and for other purposes, how can you detect this?
> As an example, suppose I have some C that uses GSL to get a random
> number if its a standalone program, or uses R's internals if its being
> compiled to run in R. I want to do something like:
> #ifdef USING_R
> #include <R.h>
> #include <gsl_random.h>
> and then:
> #ifdef USING_R
> x = rand_unif(0.0,1.0);
> x = gsl_runif(0.0,1.0);
> (cant remember the exact names but hopefully you get the idea). This
> fails because USING_R is only set when R.h is included.
So the problem is that you needed rather
x = rand_unif(0.0,1.0);
x = gsl_runif(0.0,1.0);
since if R.h is not around, the include will not include it.
> Are there any preprocessor definitions set by R CMD SHLIB and R CMD
> BUILD that I can test against?
> Of course I can stick PKG_CFLAGS=-DYES_THIS_IS_USING_R in Makevars,
> but I just wondered if there was a default solution I'd missed. Or if it
> was a good idea anyway.
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
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