cdecl and stdcall

This really is the wrong list.  Please do read the posting guide as we do 
ask (before posting).  In so far as this is relevant to R at all, it is 
within the description of the R-devel list.

I'm trying to load a dynamic link library and it seems to work 
(is.loaded -> TRUE). When I run the function, which calls the .Fortran 
subroutine, R crashes! I'v tried the same in S-Plus 2000 and it worked. 
Therefore I suppose that the dll has been compiled with the stdcall 
calling convention (and not cdecl).

Hmm.  Why do you suppose so?  In so far as I can recall S-PLUS 2000 (it is 
long obselete) it worked with cdecl (as it was built with Watcom 
compilers).  The rw-FAQ explains how to get debugging information on the 
crash, which could have many causes.

But the problem is that I don't have access to the source code, I've 
just the dll without any working import library. Maybe someone could be 
so kind and send me an example how to write a wrapper? I've found one 
example at the NAG's site 
(http://www.nag.com/numeric/RunderWindows.asp), but it didn't work. At 
http://www.cygwin.com/cygwin-ug-net/dll.html there is a description of 
linking against dlls and how to create a def and an import libraray 
file, but unfortunately my dll seems to be stripped, because I get the 
error message "no symbols" after running the command "nm".

A DLL with no symbols would be of no use to anyone, but your confusion is 
that nm does not apply to DLLs.  You need to find out what the DLL is 
exporting, with what convention.  pedump and pexports are the usual Open 
Source tools to do so.  The convention is normally hidden in the real 
symbol name, e.g. foo at 8 is a stdcall entry point, but may be aliased to 
foo.

I'm using R 2.1.0 (windows xp) and CYGWIN (gnu compilers,..)

Cygwin is not a platform we support for R.

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 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

Hi,
I'm trying to load a dynamic link library and it seems to work (is.loaded  -> TRUE). When I run the function, which calls the .Fortran subroutine, R crashes!
I'v tried the same in S-Plus 2000 and it worked. Therefore I suppose that the dll has been compiled with the stdcall calling convention (and not cdecl). But the problem is that I don't have access to the source code, I've just the dll without any working import library. Maybe someone could be so kind and send me an example how to write a wrapper? I've found one example at the NAG's site (http://www.nag.com/numeric/RunderWindows.asp), but it didn't work. At http://www.cygwin.com/cygwin-ug-net/dll.html there is a description of linking against dlls and how to create a def and an import libraray file, but unfortunately my dll seems to be stripped, because I get the error message "no symbols" after running  the command "nm".

I'm using R 2.1.0 (windows xp) and CYGWIN (gnu compilers,..)

You are likely to run into problems mixing Cygwin code with R.  R uses 
MinGW, not Cygwin.  You can probably get away with writing a DLL using 
Cygwin tools and calling it from R, but you may well find that there are 
subtle problems.  I'd suggest switching to MinGW.

The MinGW wiki gives instructions for linking to foreign DLLs on this page:

http://www.mingw.org/MinGWiki/index.php/CreateImportLibraries

For example, I've got a DLL with these exports:

$ pexports teststdcall.dll
LIBRARY teststdcall.dll
EXPORTS
dostdcall at 8

(pexports is a MinGW utility; not part of our standard toolset, but you 
can get the MinGW utils at the same place as the rest of MinGW).

Put those 3 lines in a file teststdcall.def, then

$ dlltool -d teststdcall.def -l libteststdcall.a

creates the import library.  (If your exports have names in a different 
format, you may need some different options here; see the Wiki.)

Set up your C wrapper something like this:

$ less callstdcall.c
__stdcall double dostdcall(double x);

void callit(double *x)
{
     double y;
     y = dostdcall(*x);
     *x = y;
}

You then need to set an environment variable PKG_LIBS to tell Rcmd SHLIB 
to look at your import library:

$ export PKG_LIBS="-L. -lteststdcall"

and then create your DLL to be called by R:

$ Rcmd SHLIB callstdcall.c
making callstdcall.d from callstdcall.c
gcc   -If:/R/svn/r-devel/R/include -Wall -O2   -c callstdcall.c -o 
callstdcall.o

ar cr callstdcall.a callstdcall.o
ranlib callstdcall.a
gcc  --shared -s  -o callstdcall.dll callstdcall.def callstdcall.a 
-Lf:/R/svn/r
-devel/R/src/gnuwin32  -L. -lteststdcall -lg2c -lR

Then in R

 > dyn.load('callstdcall.dll')
 > .C('callit', x=as.double( <some value> ))

will call it for you.

Duncan Murdoch

P.S. There's supposed to be a way in MinGW to avoid creating the import 
library, i.e. to link directly against the .dll, but I don't know what 
it is, and it's less flexible than this approach.