[R-pkg-devel] compileAttributes() and 'using namespace' directives

[Dirk Eddelbuettel]

Georgi,

Wrong list?  Try rcpp-devel for Rcpp question.

On 8 December 2015 at 14:37, Georgi Boshnakov wrote:
| Hi,
| 
| With a collaborator we are working on a package which uses Rcpp and RcppArmadillo.   Our *.cpp files  start with something like
| 
| // [[Rcpp::depends(RcppArmadillo)]]

Use that when you use sourceCpp() on a file. In a package, use LinkingTo:.
See the vignette Rcpp Attributes in the Rcpp package.

| #include <iostream>
| #include "RcppArmadillo.h"
| 
| using namespace arma;
| using namespace std;
| using namespace Rcpp;

I much prefer explicit namespacing in my package code (as opposed to quick
one-offs). Then again this should not break things.
 
| Running compileAttributes()  generates an RcppExports.cpp which gives errors unless we manually  add 
| 
| using namespace arma;
| 
| when everything is fine. Is this outside the scope of the automatic facilities?  
| 
| compileAttributes()   puts the corresponding directive for the Rcpp namespace but even after reading every possible source I could not figure out how to make this happen for the "arma" namespace. 

There are over 170 packages on CRAN which use RcppArmadillo. When I am stuck
on problem I often find that compare with that something similar that works
is a good approach.
 
| The same problem appears when using devtools::test() which exits with an error if RcppExports.cpp is not generated by it but if I remove that file, my understanding is that devtools::test() calls compileAttributes()  with the effect of producing invalid file and with little indication for the users what has gone wrong, besides the message "Error: Command failed (1)".

The Rcpp documentation does neither mention nor recommend devtools, so I'd
first try without it. But seems like a side effect of the earlier issue.

Dirk

-- 
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