[Rd] C Interface

[Simon Urbanek]

On Jun 18, 2010, at 10:23 AM, michael meyer <mjhmeyer at googlemail.com> wrote:

> Greetings,
> 
> I am trying to call simple C-code from R.
> I am on Windows XP with RTools installed.
> 
> The C-function is
> 
> #include <R.h>
> #include <Rinternals.h>
> #include <Rmath.h>
> #include <Rdefines.h>
> 
> // prevent name mangling
> extern "C" {
> 
> SEXP __cdecl test(SEXP s){
> 
>  SEXP result;
>  PROTECT(result = NEW_NUMERIC(1));
>  double* ptr=NUMERIC_POINTER(result);
>  double t = *REAL(s);
>  double u = t-floor(t)-0.5;
>  if(u>0) *ptr=-1+4*u; else *ptr=-1-4*u;
>  Rprintf("The value is %f", *ptr);
>  UNPROTECT(1);
>  return result;
> }
> 
> };
> 
> It is compiled with
> 
> R CMD SHLIB OrthoFunctions.c
> 
> with flag
> 
> MAKEFLAGS="CC=g++"
> 

That is entirely wrong - g++ is not a C compiler.

Cheers,
Simon


> 
> However when I call this code from R with
> 
> test <- function(t){
>  .Call("test",t)
> }
> dyn.load("./OrthoFunctions.dll")
> test(0)
> dyn.unload("./OrthoFunctions.dll")
> 
> then R crashes.
> 
> If I compile with the default flags (no extern "C", no __cdecl) I get an
> error message about an undefined reference to "__gxx_personality_v0":
> 
> C:\...>R CMD SHLIB OrthoFunctions.c
> C:/Programme/R/R-2.10.1/etc/Makeconf:151: warning: overriding commands for
> target `.c.o'
> C:/Programme/R/R-2.10.1/etc/Makeconf:142: warning: ignoring old commands for
> target `.c.o'
> C:/Programme/R/R-2.10.1/etc/Makeconf:159: warning: overriding commands for
> target `.c.d'
> C:/Programme/R/R-2.10.1/etc/Makeconf:144: warning: ignoring old commands for
> target `.c.d'
> C:/Programme/R/R-2.10.1/etc/Makeconf:169: warning: overriding commands for
> target `.m.o'
> C:/Programme/R/R-2.10.1/etc/Makeconf:162: warning: ignoring old commands for
> target `.m.o'
> g++ -I"C:/Programme/R/R-2.10.1/include"        -O2 -Wall  -c
> OrthoFunctions.c -o OrthoFunctions.o
> gcc -shared -s -o OrthoFunctions.dll tmp.def OrthoFunctions.o
> -LC:/Programme/R/R-2.10.1/bin -lR
> OrthoFunctions.o:OrthoFunctions.c:(.eh_frame+0x11): undefined reference to
> `__gxx_personality_v0'
> collect2: ld returned 1 exit status
> 
> 
> 
> I have a vague idea of the issue of calling conventions and was hoping that
> the __cdecl
> specifier would force the appropriate convention.
> I also have Cygwin installed as part of the Python(x,y) distribution but I
> am assuming that
> R CMD SHLIB source.c
> calls the right compiler.
> 
> What could the problem be?
> 
> Many thanks,
> 
> 
> Michael
> 
>    [[alternative HTML version deleted]]
> 
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