[R] Trouble with compiling or dyn.load-ing C code

[Prof Brian Ripley]

Werner,

Extension .C is for C++ code, not C code.  Please use the extension .c.

The problem is C++ name mangling.

Brian

On Tue, 28 Mar 2006, Werner Stuetzle wrote:

>
> I am trying to compile a C function and make a dll using MinGW. I
> installed MinGW, Perl, the Murdoch-Sutherland tool collection, and then I
> proceed as in "R for Windows FAQ" Section 8.
>
> Here is my C function:
> ----------------------------------------------------------------------
> /* C function adding two vectors (5-26-05)  */
>
> #include<stdlib.h>
>
> EXPORT void addvectors(double *a, double *b, int *n, double *sum) {
>   int i;
>   for (i = 0; i < *n; i++) {
>     sum[i] = a[i] + b[i];
>     }
> }
> ----------------------------------------------------------------------
>
> Here is my command to make the dll and the output:
>
> ----------------------------------------------------------------------
> z:/Stat534/Spring06/Website/Link-C-R $ c:/Progra~1/R/R-2.2.1/bin/R CMD
> SHLIB add-vectors.C
> making add-vectors.d from add-vectors.C
> g++   -Ic:/Progra~1/R/R-2.2.1/include -Wall -O2   -c add-vectors.C -o
> add-vectors.o
> ar cr add-vectors.a add-vectors.o
> ranlib add-vectors.a
> g++  --shared -s  -o add-vectors.dll add-vectors.def add-vectors.a
> -Lc:/Progra~1/R/R-2.2.1/src/gnuwin32   -lg2c -lR
> ----------------------------------------------------------------------
>
> I get "add-vectors.dll". Here is the R code to load the dll and add two
> vectors:
>
> ----------------------------------------------------------------------
> dll.filename <-
>   "z:\\Stat534\\Spring06\\Website\\Link-C-R\\add-vectors.dll"
>
> dyn.load(dll.filename)
>
> ## If the DLL needs to be re-built, it has to be unloaded first.
> ## dyn.unload(dll.filename)
>
>
> addvectors <- function(a, b) {
>   the.sum <- rep(0, length(a))
>   res <- .C("addvectors", as.double(a), as.double(b), as.integer(length(a)),
>             as.double(the.sum))
>   return(res[[4]])
> }
>
> a <- c(1,2,3)
> b <- c(4,5,6)
> addvectors(a, b)
> ----------------------------------------------------------------------
>
> Here is what I get when I use addvectors:
>
> ----------------------------------------------------------------------
>> addvectors(a, b)
> Error in .C("addvectors", as.double(a), as.double(b), as.integer(length(a)),  :
> 	C entry point "addvectors" not in load table
> ----------------------------------------------------------------------
>
>
> What am I doing wrong?
>
> Thanks a lot, W
>
>
> ----------------------------------------------------------------------
> Werner Stuetzle                           (206) 685-7431 (w)
> Professor, Statistics                     (206) 685-7419 (fax)
> Adjunct Professor, CSE                    wxs at stat.washington.edu
> Director, ACMS                            www.stat.washington.edu/wxs
> Department of Statistics, Box 354322      Office: Padelford B305
> University of Washington
> Seattle, WA 98195-4322
>
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>

-- 
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