[Rcpp-devel] tracking volatile bug

[Sokol Serguei]

Dirk Eddelbuettel has written at  Sat, 22 Nov 2014 09:57:36 -0600
> On 21 November 2014 at 23:50, Sokol Serguei wrote:
> | If I did not use the protection in my Rcpp code it's because
> | I did not see it in any example of quick ref guide:
> | http://cran.r-project.org/web/packages/Rcpp/vignettes/Rcpp-quickref.pdf
> | I didn't see any mention of PROTECT necessity neither in
> | http://dirk.eddelbuettel.com/code/rcpp/Rcpp-introduction.pdf
> | especially in the part dedicated to the use of wrap().
>
> I am sorry but that is somewhat uncalled for.
>
> We rarely advocate a programming style advocating SEXP manipulation (apart
> from rare cases, or in the guts of our code). You programmed the plain C API
> for R, apart from using some utility functions from Rcpp to access functions.
>
> For this programming style, you should go to r-devel rather than coming here.
> What you do is pretty different from standard Rcpp use, or what we recommend.
If I moved to this style it's because an Rcpp style (at least how I 
understood it) did not work for me.
Obviously, if I can get a "pure" Rcpp code working in this case I would 
be perfectly happy
with that.

>
> Blaming us
It was not a blaming, just citing my sources.
>   for not documenting what we consider inappropriate style is not
> only circular but also continues to misunderstand why we do what we do here,
> and how we do it.
May be I still misunderstand something but from what I understood
it is perfectly regular to call an R function from rcpp. Well, you say 
it is not
recommended but if there is no rcpp counterpart neither CCallable interface
what are the alternatives?

>
> | I supposed (very naively, it is clear now) that necessary wrapping and
> | protection was automagicaly added behind the stage by Rcpp.
>
> It of course happes automagically if and only if you use Rcpp datatypes.
>
> >From what I understand you did not use those, and hence got no magic.
Let try to stick with regular rcpp code
(file: matrix_norm.cpp):

//[[Rcpp::depends(RcppArmadillo)]]
#include <RcppArmadillo.h>
using namespace Rcpp;
using namespace arma;

// [[Rcpp::export]]
double nmat(mat A) {
    Function Matrix_norm_r_=Environment("package:Matrix")["norm"];
    double res=as<double>(Matrix_norm_r_(A, "1"));
    return res;
}

When called in R as:

library(Rcpp)
library(Matrix)
sourceCpp("matrix_norm.cpp")
gctorture(TRUE)
nmat(as.matrix(pi))

it gives an error:
Erreur : 'getCharCE' doit être appelé sur un CHARSXP
(my English translation: Error: 'getCharCE' must be called on CHARSXP)

Something was irregular on my side here?
Serguei.