Hi all, I have a class that stores data and various statistics about my data. I want to be able to work with it from R and from C++ functions, but I do not want to have the entire data structure created as an R object. I thought one might be able to return a pointer from the object to R, and pass that pointer from R to a C++ function that needs to interact with the object. This seems to work until garbage collection occurs, at which point I get a segfault.
I have included an example below illustrating my current approach. I altered the World example to return a pointer to the current object. I have a C++ function that makes changes to the object. I saw this post http://lists.r-forge.r-project.org/pipermail/rcpp-devel/2011-December/003214.html but I wanted to use modules and I haven't been able to adapt that solution to my situation. Any help/advice is much appreciated, Chris library(inline) library(Rcpp) fx <- cxxfunction(,"",includes= ' #include <Rcpp.h> class World { public: World() : msg("hello") {} void set(std::string msg) { this->msg = msg; } std::string greet() { return msg; } SEXP ptr() { return wrap(XPtr<World>(this, true)); } private: std::string msg; }; int fn(SEXP ptr_) { World *s = XPtr<World>(ptr_); s->set("c++ function has been here"); return 1; } RCPP_MODULE(example){ using namespace Rcpp ; function("fn", &fn); class_<World>( "World") .constructor() .method( "greet", &World::greet , "get the message") .method( "set", &World::set , "set the message") .method( "ptr", &World::ptr , "get a pointer"); } ', plugin="Rcpp") example <- Module("example",getDynLib(fx)) s <- new(example$World) # Interact with World object from R s$greet() s$set("hello from R") s$greet() # Grab pointer to this World object s$ptr() # Call a c++ function that uses World object example$fn(s$ptr()) s$greet() # c++ function has altered s, as desired # Causes segfault gc()
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