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

[Simon Fuller]

Hello Davor,

Yes, I think - I have:
#ifndef HEADERNAME_IN_CAPS
#define HEADERNAME_IN_CAPS 1
(..code..)
#endif
for all my headers.

As far as I can tell the problem arises when fstream includes
codecvt.h, which calls, on line 42:

_GLIBCXX_BEGIN_NAMESPACE(std)

I don't think this pertains to my own header includes, but I could very well
be wrong.

Thanks,

Simon


On Tue, Oct 11, 2011 at 5:27 AM, Davor Cubranic <cubranic at stat.ubc.ca>wrote:

> Hi Simon,
>
> Are you wrapping your header file with an #ifndef to prevent it from being
> included multiple times?
>
> Davor
>
>
> On October 10, 2011 03:01:33 PM Simon Fuller wrote:
> > Hello,
> >
> > I am getting some problems further down the line. It seems to happen when
> I
> > am including a std header in my own class, and when it itself includes a
> > header. Which suggests the problem is not with including headers in
> > general.
> >
> > When it is reading my header, it gets this error in fstream:
> >
> > In file included from /usr/include/c++/4.5/fstream:42:0,
> >                  from
> > /home/simon/College/PackageOne/src/MyClass/MyClass.h:6,
> >                  from file8ffc305.cpp:37:
> > /usr/include/c++/4.5/bits/codecvt.h: In function ‘SEXPREC*
> > file8ffc305(SEXPREC*, SEXPREC*)’:
> > /usr/include/c++/4.5/bits/codecvt.h:42:1: error: expected ‘=’ before
> > ‘__attribute__’
> > /usr/include/c++/4.5/bits/codecvt.h:42:1: error: expected identifier
> before
> > ‘__attribute__’
> > /usr/include/c++/4.5/bits/codecvt.h:42:1: error: expected ‘;’ before
> > ‘__attribute__’
> > /usr/include/c++/4.5/bits/codecvt.h:42:1: error: expected
> > primary-expression before ‘__attribute__’
> > /usr/include/c++/4.5/bits/codecvt.h:42:1: error: expected ‘;’ before
> > ‘__attribute__’
> >
> > In fstream, line 42 is indeed: #include <bits/codecvt.h>
> >
> > I checked /usr/include/c++/4.5/bits/codecvt.h:42:1:
> >
> > and this is line 42 of codecvt.h:
> >
> > _GLIBCXX_BEGIN_NAMESPACE(std)
> >
> > I googled this function, and I am wondering if it might be a
> compatibility
> > issue, as this sometimes seems to be cited in this regard in forums. I
> > really do not know myself. Has anyone any suggestions?
> >
> > Thanks,
> >
> > Simon
> >
> >
> >
> >
> > On Mon, Oct 10, 2011 at 11:09 AM, Simon Fuller
> > <simonfuller9 at gmail.com>wrote:h
> >
> > > Hello,
> > >
> > > I have just joined the mailing list.
> > >
> > > I was hoping you might be able to help me with a question.
> > >
> > > I am new to Rcpp, have some experience with both R and C++, but very
> > > little experience with integrating languages.
> > >
> > > I hope to use Rcpp to develop code over the next few years. However, to
> > > begin with, I have some preexisting C++ classes that I would like to
> make
> > > available to R.
> > >
> > > I have read the documentation that I can find, but I do not know which
> is
> > > the best approach to take.
> > >
> > > I only, in principle, need *one method* to interact with the classes -
> > > there then follows a fairly arduous process using different tree
> > > structures each of which have aggregate classes, but only a single
> > > double needs to be returned to R.
> > >
> > > I was therefore hoping to simply call a C++ wrapper function in-line,
> > > remotely, which in turn called my classes, but that does not work. I
> get
> > > an: "expected unqualified-id before ‘extern’ " error after my includes,
> > > at: RcppExport SEXP..  at the start of my method declaration. (I can
> > > post code if this approach is not a complete dead end)
> > >
> > > So my two questions are: is there a quick way of prototyping this? i.e.
> > > to get R to invoke my classes through an rcpp intermediary.
> > >
> > > If there is not a quick way to do this, what is the best approach? Do I
> > > need to, and if so how do I, make my classes accessible to Rcpp.
> Because
> > > my whole hope here is to use preexisting code as swiftly as possible,
> > > 'easiest' and 'quickest' are almost synonyms for 'best' in my question.
> > >
> > > If someone could point me in the direction of some example code where
> > > Rcpp invokes user classes this would be great.
> > >
> > > My apologies if my question has been covered before, but I would really
> > > appreciate some advice on what is and is not possible, and some
> strategic
> > > advice on the best (easiest and quickest) approach.
> > >
> > > Thank you for your help. It is deeply appreciated.
> > >
> > > Simon
>
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