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

[Simon Fuller]

Hello again,

I think I figured it out. I was messing up user includes by not using
readLines. I then had the further epiphany that I could just c() include the
cpp file as well there, because it is really just copying and pasting the
text, so it can copy and paste any text you throw at it.

Great stuff lads. Hope I have enough to go on now to get my classes working
- should do.

I will look into building packages then - that vignette looks pretty useful.


Thanks all,

Simon



On Wed, Oct 12, 2011 at 12:59 PM, Simon Fuller <simonfuller9 at gmail.com>wrote:

> 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)
>> _______________________________________________
>> Rcpp-devel mailing list
>> Rcpp-devel at lists.r-forge.r-project.org
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>>
>
>
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