R help - Jul 2003 - Problems with a dll under windows

I am trying to get a dll compiled for use with dyn.load. I use R.1.7.1
under Windows.

I have tried the following trivial example based on the "Writing R
extensions" manual.

rtest.h
--------
class X {
public:
    X ();
    ~X ();
    void Give7(double*);
};

class Y {
public: Y (); ~Y ();
};

rtest.cpp
---------
#include <iostream.h>
#include "rtest.h"

static Y y;


extern "C" {

    void X_main () {
            X x;
    }
}

X::X()   { std::cout << "construct X" << std::endl; }
X::~X()  { std::cout << "destruct X"  << std::endl; }
Y::Y()   { std::cout << "construct Y" << std::endl; }
Y::~Y()  { std::cout << "destruct Y"  << std::endl; }

//silly function to test returning a constant double
void X::Give7(double * a)   
{
    *a=7;
}
---- end rtest.cpp

Then I create the dll using the following DOS command
   Rcmd SHLIB rtest.cpp
(I have all the perl, MINGW and related stuff set up as
per the instructions at http://www.stats.ox.ac.uk/pub/Rtools/)

Then in R, I type the following.
> x <- 3
> dyn.load("rtest.dll")
So far, so good.

Then...PROBLEM 1
> .C("Give7",x)
Error in .C("Give7", x) : C/Fortran function name not in load table

How do you convince the compiler to use the name "Give7" as an entry
point?

And PROBLEM 2...
I checked the DLL and the names have been decorated.
If I use the decorated name I get the following:
> .C("_ZN1X5Give7EPd",x)
[[1]]
[1] 3

For some reason, it is not altering x as it should.

What am I doing wrong?

Thanks.
Rob Hyndman
___________________________________________________
Rob J Hyndman
Associate Professor & Director of Consulting
Department of Econometrics & Business Statistics
Monash University, VIC 3800, Australia.
http://www-personal.buseco.monash.edu.au/~hyndman/

On Mon, 07 Jul 2003 13:49:01 +1000, you wrote:
>//silly function to test returning a constant double
>void X::Give7(double * a)   
>{
>    *a=7;
>}
>---- end rtest.cpp
>
>Then I create the dll using the following DOS command
>   Rcmd SHLIB rtest.cpp
>(I have all the perl, MINGW and related stuff set up as
>per the instructions at http://www.stats.ox.ac.uk/pub/Rtools/)
>
>Then in R, I type the following.
>> x <- 3
>> dyn.load("rtest.dll")
>So far, so good.
>
>Then...PROBLEM 1
>> .C("Give7",x)
>Error in .C("Give7", x) : C/Fortran function name not in load
table
A call to Give7 needs to pass both an instance of X and a.  You're
only passing a, because R doesn't know anything about instances of X.

Generally speaking, R can only call standard C functions, not C++
methods.  Your example seems to be based on the Writing R Extensions
section 4.6 example, but you miss the last part of it:  R can only
call X_main, not X::Give7.

Duncan Murdoch
>
>How do you convince the compiler to use the name "Give7" as an
entry
>point?
>
>And PROBLEM 2...
>I checked the DLL and the names have been decorated.
>If I use the decorated name I get the following:
>> .C("_ZN1X5Give7EPd",x)
>[[1]]
>[1] 3
>
>For some reason, it is not altering x as it should.
>
>What am I doing wrong?
>
>Thanks.
>Rob Hyndman
>___________________________________________________
>Rob J Hyndman
>Associate Professor & Director of Consulting
>Department of Econometrics & Business Statistics
>Monash University, VIC 3800, Australia.
>http://www-personal.buseco.monash.edu.au/~hyndman/
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://www.stat.math.ethz.ch/mailman/listinfo/r-help