Hi,
I’m currently working on a header-only library that it intended to act as a
“glue" layer between an existing C++11 library (also header only) and R, by
means of Rcpp.
Basically, I am trying to provide some generic templates that perform
operations using the existing C++11 library and return appropriate data objects
to the R environment.
My current plan for this library is that:
1. It is also c++11
2. It exists in its own namespace
Rcpp seems to have problems with the latter, but only on GCC. I am unable to
return XPtr to objects whose names are typedefs within a namespace. However,
everything works using clang++.
A reproducible example of this issue can be found at
https://gist.github.com/molpopgen/989ec678664d083bf4a3
<https://gist.github.com/molpopgen/989ec678664d083bf4a3>
Version numbers are:
Rcpp - 0.11.6
R - 3.1.0
g++ - 4.9.2
clang++ — 3.5 and 3.6
Ubuntu 14.04 LTS
I first discovered this when code I’d implemented on OS X/Yosemite/clang failed
to link on my Linux box, where g++ is the default.
If you have git on your system and g++ as your default CXX, then
git clone https://gist.github.com/molpopgen/989ec678664d083bf4a3
<https://gist.github.com/molpopgen/989ec678664d083bf4a3>
cd 989ec678664d083bf4a3
##This fails on my system with GCC w/no deleter for the XPtr found, but it
compiles fine if I set ~/.R/Makevars to say CXX=clang++-3.6
Rscript doit.R
##This works with any of the compilers on my Ubunutu system, because I provide
a custom deleter for the XPtr
Rscript doit2.R
If you look at the comments in the C++ code in the gist, this issue arises due
to a strange mix of typedefs in a namespace + a template function in the same
namespace. However, I don’t think that this is an unusual use case. Looking
at the XPtr implementation, I don’t see any reason for the symbol not to be
generated.
Thanks,
Kevin
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