[Rcpp-devel] Question regarding integrating preexisting C++ code via Rcpp

[Simon Fuller]

Hello Darren,

Thank you for your advice. It makes good sense.

I now have a linker problem, and I have written some code to abstract the
problem for your viewing.

The error message is:
"Error in dyn.load(libLFile) :
  unable to load shared object '/tmp/RtmpBFr1mw/file44b636b6.so':
  /tmp/RtmpBFr1mw/file44b636b6.so: undefined symbol:
_Z6sumvecSt6vectorIiSaIiEE"

It seems safe to say that it cannot find the cpp file for LinkTest.h

The problem might be with how to use the"includes" argument for cxxfunction
(see 1.b below).

It seems a common enough problem, but I have not been able to gain a clearer
understanding by reading past comments on it, as most of these seem to
pertain to packages. So I will post the relevant code here, and the full
output from verbose=TRUE below it:

1. R Calling Function
linktest<-cxxfunction( signature( vec = "numeric", len = "integer" ), paste(
readLines(
"/home/simon/College/PackageOne/src/BZip/LinkTestWrap.cpp"),collapse = "\n"
) , plugin = "Rcpp",verbose=TRUE )

1.b I also tried using user includes in the cxxfunction, and taking them out
of the cpp file. But they don't seem to be parse properly in the created
code, i.e.:
"// user includes
  /home/simon/College/PackageOne/src/BZip/LinkTest.h"
 which the compiler naturally flags.


2. LinkTestWrap.cpp: Rcpp Wrapping Function (for use by inline)
#include <Rcpp.h>
#include <vector>
#include "/home/simon/College/PackageOne/src/BZip/LinkTest.h"

    using std::vector;

    vector<int> input_vector( as< vector<int> >( vec ) );
    int length = as<int> ( len );

    int res = sumvec( input_vector );

    return Rcpp::wrap( res );

3. LinkTest.h
#include <vector>
int sumvec(std::vector<int> vec);

4.LinkTest.cpp
#include "/home/simon/College/PackageOne/src/BZip/LinkTest.h"

using std::vector;

int sumvec(vector<int> vec){
    int total = 0;
    for( vector<int>::const_iterator it = vec.begin(); it != vec.end(); ++it
){
        total += *it;
    }
    return total;
}

Thanks again,

Simon



I thought the problem is with inline though. To take the link you gave:
http://stackoverflow.com/questions/3221422/gcc-template-error
One answer cites: "The errors that you have posted suggest that the problem
is within the function void init_module_PyCML(). It would therefore appear
that you have tried to define a function template within the body of another
function." I interpreted this to be due to inline because the problem with
static member variables certainly seems to be because the class and other
code is defined within a wrapper function by inline.

On Wed, Oct 12, 2011 at 12:24 AM, Darren Cook <darren at dcook.org> wrote:

> > My apologies for not posting comprehensive code. My intention was only to
> > lessen the reading burden for you.
>
> Don't post comprehensive code :-)
> But if you can discover the smallest possible example that shows the
> problem, that will encourage lots of helpful responses.
>
>
> > I am currently getting this error:
> >
> > /home/simon/College/PackageOne/src/BZip/BinaryTree.h: In function
> ‘SEXPREC*
> > file354d98a8(SEXPREC*, SEXPREC*)’:
> > /home/simon/College/PackageOne/src/BZip/BinaryTree.h:8:1: error: expected
> > primary-expression before ‘template’
> > /home/simon/College/PackageOne/src/BZip/BinaryTree.h:8:1: error: expected
> > ‘;’ before ‘template’
>
>
> This is saying that you've not finished a statement before defining
> another one. E.g. see
>  http://stackoverflow.com/questions/3221422/gcc-template-error
>
> It could mean a missing semi-colon in the file being included before
> this one. If there are no statements or #include lines before line 8 in
> BinaryTree.h, look at the files that include BinaryTree.h.
>
> >  I think I can see a quick solution, (not to use the template - I don''t
> > need genericity here anyway,)...
>
> If that is true, then the Smallest Possible Example would be very
> interesting to the Rcpp developers, I'm sure.
>
> Darren
>
>
> --
> Darren Cook, Software Researcher/Developer
>
> http://dcook.org/work/ (About me and my work)
> http://dcook.org/blogs.html (My blogs and articles)
> _______________________________________________
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