[R] Include C++ DLL, error in ...: C symbol name not in load table

[Sascha Vieweg]

Hello R experts

I am googling and reading around, however, I can't get it working 
(perhaps because I do not understand much C, however, I'll give it 
a try). I am trying to include C++ code into an R routine, where 
the C++ code looks:

#include <iostream>
using namespace std;
void foo (double* x, double* y, double* out)
{
 	out[0] = x[0] + y[0];
}

Back in R, the command

R CMD SHLIB --preclean -o xplusy

works fine resulting in two new files, xplusy.o and xplusy.so. The 
wrapper in R is:

dyn.load("xplusy.so")
xplusy <- function(x, y){
   .C("foo", as.double(x), as.double(y), out=double(1))$out
}
xplusy(1, 2)
dyn.unload("xplusy.so")

Now, dyn.load() works and xplusy also shows up in getLoadedDLLs(). 
However, when invoking the function, xplusy(1, 2), R complains:

Error in .C("foo", as.double(x), as.double(y), out = double(1)): C 
symbol name "foo" not in load table

I found some hints concerning Fortran code producing this error 
message, but no help concerning C code.

Any help tips?

Thanks, *S*

$. uname -a
Darwin * 10.7.3 Darwin Kernel Version 10.7.3[...]

$: c++ --version
i686-apple-darwin10-g++-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5666) 
(dot 3)

platform       i386-apple-darwin9.8.0
arch           i386
os             darwin9.8.0
system         i386, darwin9.8.0
status
major          2
minor          12.2
year           2011
month          02
day            25
svn rev        54585
language       R
version.string R version 2.12.2 (2011-02-25)

-- 
Sascha Vieweg, saschaview at gmail.com