[Rcpp-devel] Resolving NativeSymbolInfos from Rcpp (revisited)

[JJ Allaire]

The best you can do is to get the pointer to the function (not sure if that
does what you are hoping for):

func <- Rcpp::cppFunction("int foo() { return 1; }")

> body(func)
.Primitive(".Call")(<pointer: 0x103bf0f40>)


On Fri, Jul 28, 2017 at 8:00 PM, Iñaki Úcar <i.ucar86 at gmail.com> wrote:

> 2017-07-29 0:29 GMT+02:00 Dirk Eddelbuettel <edd at debian.org>:
> >
> > On 28 July 2017 at 19:14, Iñaki Úcar wrote:
> > | Hi all,
> > |
> > | I found this interesting thread by Davor Cubranic in which Romain came
> > | up with a solution for calling a C routine from the 'stats' package:
> > | http://lists.r-forge.r-project.org/pipermail/rcpp-
> devel/2010-June/000753.html
> > |
> > | In a nutshell, I would like to do the same, but with a user-provided
> > | function compiled with Rcpp::cppfunction. Namely,
> > |
> > | 1) get the externalptr
> > | 2) get the DL_FUNC with R_ExternalPtrAddrFn
> > | 3) use it
> > |
> > | Thanks to Romain, 2) and 3) are straightforward. The problem is the
> > | first step. I saw that, if I compile a function like this
> > |
> > | > Rcpp::cppFunction("int foo() { return 1; }")
> > |
> > | then I can obtain the externalptr with
> > |
> > | > getNativeSymbolInfo("sourceCpp_ID_foo")
> > |
> > | but the problem is that you have to figure out this ID. Is there a
> > | general way to obtain the name of the native symbol that Rcpp
> > | produces? (Also I suppose that the initial "sourceCpp_" part could
> > | change in the future).
> >
> > I recall that clever trick.
> >
> > The problem is that R Core really does not want us to access such
> unexported
> > access points.
>
> R Core may or may not want us to do 2) and 3), AKA the tricky part.
> But all I'm asking is how to get the externalptr from a cppFunction,
> which is just another (*kinda*) valid R data type. ;) R core provides
> getNativeSymbolInfo and Rcpp sets up the symbol name: it should be
> easy for Rcpp to expose the externalptr (if it's not already the
> case).
>
> Iñaki
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