C Interface

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 OrthoFunctions.c

with flag

MAKEFLAGS="CC=g++"

However when I call this code from R with

test <- function(t){
 .Call("test",t)
}
dyn.load("./OrthoFunctions.dll")
test(0)
dyn.unload("./OrthoFunctions.dll")

then R crashes.

If I compile with the default flags (no extern "C", no __cdecl) I get an
error message about an undefined reference to "__gxx_personality_v0":

C:\...>R CMD SHLIB OrthoFunctions.c
C:/Programme/R/R-2.10.1/etc/Makeconf:151: warning: overriding commands for
target `.c.o'
C:/Programme/R/R-2.10.1/etc/Makeconf:142: warning: ignoring old commands for
target `.c.o'
C:/Programme/R/R-2.10.1/etc/Makeconf:159: warning: overriding commands for
target `.c.d'
C:/Programme/R/R-2.10.1/etc/Makeconf:144: warning: ignoring old commands for
target `.c.d'
C:/Programme/R/R-2.10.1/etc/Makeconf:169: warning: overriding commands for
target `.m.o'
C:/Programme/R/R-2.10.1/etc/Makeconf:162: warning: ignoring old commands for
target `.m.o'
g++ -I"C:/Programme/R/R-2.10.1/include"        -O2 -Wall  -c
OrthoFunctions.c -o OrthoFunctions.o
gcc -shared -s -o OrthoFunctions.dll tmp.def OrthoFunctions.o
-LC:/Programme/R/R-2.10.1/bin -lR
OrthoFunctions.o:OrthoFunctions.c:(.eh_frame+0x11): undefined reference to
`__gxx_personality_v0'
collect2: ld returned 1 exit status



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

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