[R] load C code into R

Prof Brian Ripley ripley at stats.ox.ac.uk
Mon Jun 11 11:31:35 CEST 2001

On Sun, 10 Jun 2001, Richard Condit wrote:

> I am trying to load C routines into R on windows, going through the the
> book S programming and the R manual, but I know I am missing some steps.
> I created a win32 DLL project in Visual C++ (ver. 6.0).  It consists of one
> simple routine named test which accepts one *integer argument and one
> *double argument and performs a trivial computation.  The dll is named
> test.dll.
> In R1022 for Windows, I run
>  >dyn.load("d:/programs/library/test/test.dll")
>  >testr_function(a,x)
> .C"d:/programs/library/test/test",as.integer(a),as.double(x))
> These are both accepted, and I can use dyn.unload as well with test.dll.  I
> notice that while loaded, Visual C++ cannot recompile test.dll.

Yes, that's a feature of Windows (and some other OSes).

> But when I try
>  >testr(10,x)
> I get the message “Error in .C("test", as.integer(a),as.double(x)) :
> C/Fortran function name not in load table”.
> I know I need a link step, or an install step, but I am missing something
> in the instructions.  Perhaps just a quick piece of advice could get me to
> the next stage…

Your .C call should be something like

.C("test", as.integer(a), as.double(x))

and "test" must be exported by your DLL.  Note: by default nothing is
exported in Visual C++: you need a .def file in the project.

I think you've missed the advice in readme.packages (in rw1023sp.zip),
which has a section `Using Visual C++'.  Despite the presence of that,
using the recommended compiler is easier....

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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