Unable to find compiled C++ functions in R package

Question

I'm having difficulty integrating C++ functions into my R package. I'm following Hadley's guide step by step, and I'm curious if perhaps it needs an update. I created a tiny test package for reproducibility.

To create this package, I follow these steps:

(1) Create the call_times_two function in hello.R .

(2) Call devtools::document() .

(3) Call usethis::use_rcpp() .

(4) Add the suggested roxygen tags to R/rcpptest-package.R .

(5) Add Hadley's timesTwo function to src/code.cpp .

(6) Call devtools::document() again.

(7) Build and reload the package.

No errors were encountered in any of the above steps.

Then, I attempt to call my call_times_two function as

# Expected output of 6
rcpptest::call_times_two(3)

However, when I call this function I get the following error:

Error in .Call("_rcpptest_timesTwo", PACKAGE = "rcpptest", x) : 
  "_rcpptest_timesTwo" not available for .Call() for package "rcpptest"

Does anyone know why this is happening?

Answer 1

Maybe that guide or version is outdated? We have supported Rcpp.packages.skeleton() pretty much since Rcpp was first released.

Create

$ Rscript -e 'Rcpp::Rcpp.package.skeleton("rcpptest")'
Creating directories ...
Creating DESCRIPTION ...
Creating NAMESPACE ...
Creating Read-and-delete-me ...
Saving functions and data ...
Making help files ...
Done.
Further steps are described in './rcpptest/Read-and-delete-me'.

Adding Rcpp settings
 >> added Imports: Rcpp
 >> added LinkingTo: Rcpp
 >> added useDynLib directive to NAMESPACE
 >> added importFrom(Rcpp, evalCpp) directive to NAMESPACE
 >> added example src file using Rcpp attributes
 >> added Rd file for rcpp_hello_world
 >> compiled Rcpp attributes 
$ 

Install

$ R CMD INSTALL rcpptest
* installing to library ‘/usr/local/lib/R/site-library’
* installing *source* package ‘rcpptest’ ...
** using staged installation
** libs
ccache g++-11 -I"/usr/share/R/include" -DNDEBUG  -I'/usr/local/lib/R/site-library/Rcpp/include'    -fpic  -g -O3 -Wall -pipe   -c RcppExports.cpp -o RcppExports.o
ccache g++-11 -I"/usr/share/R/include" -DNDEBUG  -I'/usr/local/lib/R/site-library/Rcpp/include'    -fpic  -g -O3 -Wall -pipe   -c rcpp_hello_world.cpp -o rcpp_hello_world.o
ccache g++-11 -Wl,-S -shared -L/usr/lib/R/lib -Wl,-Bsymbolic-functions -flto=auto -Wl,-z,relro -o rcpptest.so RcppExports.o rcpp_hello_world.o -L/usr/lib/R/lib -lR
installing to /usr/local/lib/R/site-library/00LOCK-rcpptest/00new/rcpptest/libs
** R
** byte-compile and prepare package for lazy loading
** help
*** installing help indices
** building package indices
** testing if installed package can be loaded from temporary location
** checking absolute paths in shared objects and dynamic libraries
** testing if installed package can be loaded from final location
** testing if installed package keeps a record of temporary installation path
* DONE (rcpptest)
$ 

Use

> library(rcpptest)
> rcpp_hello_world()
[[1]]
[1] "foo" "bar"

[[2]]
[1] 0 1

>