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

[Duncan Murdoch]

On 20/04/2011 4:38 PM, Dirk Eddelbuettel wrote:
>
> On 20 April 2011 at 16:24, Duncan Murdoch wrote:
> | On 20/04/2011 4:06 PM, Sascha Vieweg wrote:
> |>  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.
> |
> | You have C++ code, not C code.  C++ normally mangles names of exports.
> |
> | To get this to work, you should surround your declarations with
> |
> | extern "C" {
> | }
> |
> | Another possibility is to use the Rcpp package; it writes the interface
> | code for you.
>
> I believe Duncan refers to the 'inline' package, rathern than 'Rcpp' (which
> itself uses 'inline').

Oops, Dirk is right.

Duncan Murdoch