Hi Dirk, I found a more generic solution than a singleton class. I'm extracting the pointer out of the `std::unique_ptr` using `release`, and putting it into a `std::shared_ptr`. This one can easily be wrapped using the standard Rcpp mechanisms.
This is maybe not the best way to do it, I also followed your recommendation to look into `Rcpp::XPtr`, and it seems that it should be possible to pass it a raw pointer and construct a SEXP around it. But that's more code to write, I like the simple solutions... Many thanks for your help! Cris. On 12 April 2018 at 05:42, Dirk Eddelbuettel <e...@debian.org> wrote: > > On 11 April 2018 at 23:54, Cris Luengo wrote: > | > The way R thinks about this is that _it_ owns everything, and Rcpp > makes > | > getting things back and forth _using the R memory system and its > lifetime / > | > reference count control_ fairly easy. > | > | Yes, that makes sense. But somehow it is not easy to transfer ownership > | of an object to R. There needs to be a new object created that it can > own? > > Yes, in general that works just fine. Ie when we do > > Rcpp::NumericVector x(10); > > we use the R malloc functions, and to R this _is_ the same as a REAL with > 10 > elements. Because everything has to be a SEXP, our C++ objects are really > proxies to underlying SEXPs. And R is happy. And controls everything and it > all works as if you used the C API of R. Which we extend (by a lot, you > could say) to make things easier. > > A unique_ptr with _control on the C++ side_ does not fit that mold at all > so > we have to do something different here. The singleton / static instance is > one approach _so that it survives across multiple (different) calls_ from > R. > > I am sure there are other approaches, but they still have to match the > basic > constraint of 'SEXP in, SEXP out'. > > Hth, Dirk > > -- > http://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org >
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