Hello,
This is not the appropriate mailing list. Use R-devel for questions
about C, etc ...
One thing that might help you is the inline package.
require( inline )
fx <- cfunction( signature( s = "numeric" ), '
SEXP result;
PROTECT(result = NEW_NUMERIC(1));
double* ptr=NUMERIC_POINTER(result);
double t = *REAL(s);
double u = t-floor(t)-0.5;
if(u>0) *ptr=-1+4*u; else *ptr=-1-4*u;
Rprintf("The value is %f", *ptr);
UNPROTECT(1);
return result;
', verbose = TRUE )
fx( 10 )
The verbose = TRUE argument will show you how inline runs the show.
Romain
Le 18/06/10 16:18, michael meyer a écrit :
Greetings,
I am trying to call simple C-code from R.
I am on Windows XP with RTools installed.
The C-function is
#include<R.h>
#include<Rinternals.h>
#include<Rmath.h>
#include<Rdefines.h>
// prevent name mangling
extern "C" {
SEXP __cdecl test(SEXP s){
SEXP result;
PROTECT(result = NEW_NUMERIC(1));
double* ptr=NUMERIC_POINTER(result);
double t = *REAL(s);
double u = t-floor(t)-0.5;
if(u>0) *ptr=-1+4*u; else *ptr=-1-4*u;
Rprintf("The value is %f", *ptr);
UNPROTECT(1);
return result;
}
};
It is compiled with
R CMD SHLIB source.c
If you want C++, then name your file source.cpp
SHLIB compiles files with .c extensions with a C compiler, which will
not be happy about extern "C"
with flag
MAKEFLAGS="CC=g++"
If I compile with the default flags I get an error message about an
undefined reference to "__gxx_personality_v0".
However when I call this code from R with
test<- function(t){
.Call("test",t)
}
dyn.load("./source.dll")
test(0)
dyn.unload("./source.dll")
then R crashes.
I have a vague idea of the issue of calling conventions and was hoping that
the __cdecl
specifier would force the appropriate convention.
I also have Cygwin installed as part of the Python(x,y) distribution but I
am assuming that
R CMD SHLIB source.c
calls the right compiler.
What could the problem be?
Many thanks,
Michael
--
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
|- http://bit.ly/98Uf7u : Rcpp 0.8.1
|- http://bit.ly/c6YnCi : graph gallery collage
`- http://bit.ly/bZ7ltC : inline 0.3.5
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