[R-pkg-devel] R package with external C++ library

Hi,

I would like to port Google's s2-library for spherical geometry (see 
e.g. https://github.com/micolous/s2-geometry-library for a fork on 
GitHub). It is not a standard library that can easily be installed on 
various systems, so I would like to include the source code in the R 
package. The catch is that I would like to modify the source code as 
little as possible :-)

I have package everything and added configure scripts and a tiny 
R-function that calls one of the C++-functions (using the antiquated .C 
interface for now -- that will of course be changed) in this repo:
https://github.com/spatstat/s2

It compiles into a working package on Ubuntu (travis-ci + my laptop), 
OSX (travis-ci), and Windows (appveyor + my surface pro), but R CMD 
check produces some warnings (and a note about the size of the shared 
object, but I assume that is less important).

The main things seem to be related to (travis log is at 
https://travis-ci.org/spatstat/s2/jobs/149578339):

1. Deprecated C++ headers <ext/hash_set> and <ext/hash_map>.

2. Compiled code that calls entry points which might terminate R or 
write to stdout/stderr.

Is it hopeless to get on CRAN with warnings like these?
I'm not very used to writing C/C++ code, but I guess 1. can be fixed by 
a few sed commands with the replacement headers and corresponding new 
function names. Point 2. can probably also be fixed with a reasonable 
effort, but I haven't investigated yet, and I would like an opinion from 
the list before spending more time on this. In more generality the 
question could be phrased something like:

"When including C++ code from an upstream library which you do not 
control should R CMD check be completely spotless or is some flexibility 
to be expected in these circumstances?"

Cheers,
Ege

PS: Extra question (prehaps particularly aimed at Dirk): When I will 
actually start to use the C++ library I expect it could be beneficial to 
use Rcpp. I have seen RcppModules mentioned somewhere, and I wonder if 
such an external C++ library would make sense to interface via 
RcppModules (again aiming at changing upstream sources as little as 
possible)?

Ege Rubak, Associate Professor,
Department of Mathematical Sciences, Aalborg University
Fredrik Bajers Vej 7G, 9220 Aalborg East, Denmark
Phone: (+45)99408861
Mobile: (+45)30230252
Email: rubak at math.aau.dk