[Swig-devel] Code to reproduce: swig-R regression - out typemaps invalid object for slot "ref" in class should be or extend class "externalptr"

[Matt H. <mat...@gm...>]

Hi all,

I'm interested in getting the R bindings working for the shogun
machine learning library and I'm running into the problem that was
discussed in this thread:

http://sourceforge.net/p/swig/mailman/message/32022817/

I was able to modify one of the existing swig R examples so that it
reproduces the error. Hopefully that will be helpful in finding the
cause of the bug. If you untar the attached file into the
swig/Examples/r directory and then run make in the directory that it
creates, you should get the error:

Error in validObject(.Object) :
  invalid class "_p_Coordinates" object: invalid object for slot "ref"
in class "_p_Coordinates": got class "numeric", should be or extend
class "externalptr"
Calls: <Anonymous> ... f -> new -> initialize -> initialize -> validObject
Execution halted

I am just using a simple typemap to convert the Coordinates class into
an R vector:

class Coordinates;

%typemap(out) Coordinates
{
  double x = $1.x;
  double y = $1.y;

  Rf_protect( $result = Rf_allocVector(REALSXP, 2) );

  REAL($result)[0]=x;
  REAL($result)[1]=y;

  Rf_unprotect(1);
}

This is being picked up in the generated c++ wrapper code:

SWIGEXPORT SEXP
R_swig_Shape_getCoordinates ( SEXP self, SEXP s_swig_copy)
{
<snip>
  arg1 = reinterpret_cast< Shape * >(argp1);
  result = (arg1)->getCoordinates();
  {
    double x = (&result)->x;
    double y = (&result)->y;

    Rf_protect( r_ans = Rf_allocVector(REALSXP, 2) );

    REAL(r_ans)[0]=x;
    REAL(r_ans)[1]=y;

    Rf_unprotect(1);
  }

  vmaxset(r_vmax);
  if(r_nprotect)  Rf_unprotect(r_nprotect);

  return r_ans;
}

but the generated R code still thinks that it is receiving a pointer
to a Coordinates object, rather than an R numeric vector:

# Start of Shape_getCoordinates

`Shape_getCoordinates` = function(self, .copy = FALSE)
{
  if (inherits(self, "ExternalReference")) self = slot(self,"ref")
  ;ans = .Call('R_swig_Shape_getCoordinates', self, as.logical(.copy),
PACKAGE='example');
  ans <- new("_p_Coordinates", ref=ans);

  ans

}

attr(`Shape_getCoordinates`, 'returnType') = '_p_Coordinates'
attr(`Shape_getCoordinates`, "inputTypes") = c('_p_Shape')
class(`Shape_getCoordinates`) = c("SWIGFunction", class('Shape_getCoordinates'))

Hopefully that's helpful!

Matt