On 10 November 2014 at 13:16, Claymore Marshall wrote:
| I want to expose to R several C++ classes from a library with Rcpp modules.
| I'm trying to imitate a similar set of Python modules that were made for the
| same library.
|
| In Boost.Python, with .def it is possible to specify the return_value_policy.
| Is it also possible to do this in a straight forward way with Rcpp modules
when
| exposing C++ class methods?
|
| The following simplified example illustrates a problem I face with using Rcpp
| modules. When R deletes 'res', R crashes shortly after (a segfault?).
|
| With a Python module, this kind of problem apparently doesn't come about by
| setting in .def the following:
return_value_policy<reference_existing_object>()
|
|
| Is there an easy way to get around this problem with Rcpp modules with minimal
| code?
|
| #include <Rcpp.h>
| using namespace Rcpp;
|
| class A {
|
| public:
|
| A(int x_) : x(x_){}
|
| int x;
| };
|
| class B {
|
| public:
| B():m_A(10) {}
|
| A get_an_A(){
| A an_A(3);
| return an_A;
| }
| A * get_member_A() { return & m_A; }
|
| private:
| A m_A;
| };
|
| RCPP_EXPOSED_CLASS(A)
| RCPP_EXPOSED_CLASS(B)
|
| RCPP_MODULE(AB_mod){
| using namespace Rcpp ;
| class_<A>("A")
| .constructor<int>()
| .field("x", &A::x)
| ;
| class_<B>("B")
| .constructor()
| .method("get_an_A",&B::get_an_A)
| .method("get_member_A", &B::get_member_A)
| ;
| }
|
|
|
| ------------------------
|
| R code:
|
| A_eg <- new(A, 10)
| B_eg <- new(B)
|
| res <- B_eg$get_member_A()
|
| rm(res)
| # R crashes shortly after running further commands ...
| # How can this error be prevented?
By not removing res?
By adding a finalizer / destructor for it?
I don't use modules for things I add / remove frequently from the heap. I
generally just create an object "and keep it". That usage works for me.
Dirk
--
http://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org
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