Question about Running C code from R

Dear R-devel,

Apologies for sending what is probably a very simple question to 
R-devel: I am definitely missing something very simple and can't work 
out what it is. I've been trying to find the problem here for about a 
month and need some help!

I am trying to work out how to run a C program from an R script. Rather 
than try the C program directly, I'm trying to get a much simpler piece 
of code to work as a proof-of-concept. Here's the C code (simplecall.c):

***********************************************************************************************
#include <stdio.h>
#include <Rinternals.h>
#include <R_ext/Rdynload.h>

int Rc(int a) {
return (a+3);
}

SEXP Rc2(SEXP a) {
return(18); //LINE A
// return(ScalarReal(REAL(a)[0]+12)); //LINE B
}

int main()
{
int i,j;
SEXP m,n;

i=4;j=Rc(i);
printf("\nUsing Rc: %i+3=%i - OK so far.\n",i,j);

m=6;n=Rc2(m);
printf("\nUsing Rc2: %i+12=%i - Doing well.\n",m,n);

printf("\nPress <ENTER> ...\n");
getchar();
return 0;
}
***********************************************************************************************

and I've compiled this (using the only C compiler I have, which is a 
Borland C++ Builder which insists on calling the executable 
"Project.exe"). I managed to get it to compile correctly with the two R 
includes at the front and the two functions work OK when I run the C 
executable. What I want to do is access these functions from R, however. 
Here's the R code I've written (simplecall.r), which I've put together 
from various websites and guesses:

***********************************************************************************************
dll=dyn.load("Project1.exe")
syms=getNativeSymbolInfo(c("Rc","Rc2"),dll)

RcInR=function(x) {
.Call(dll$Rc,as.numeric(x))
}

Rc2InR=function(x) {
.Call(dll$Rc2,as.numeric(x))
}

i1=4;j1=Rc(i1)
cat("\nUsing Rc from R: ",i1,"+3=",j1," - OK so far.\n")

m1=6;n1=Rc2(m1)
cat("\nUsing Rc2 from R: ",m1,"+12=",n1," - Doing well.\n");

***********************************************************************************************

Basically, there are two problems (at least!). If I have LINE A in the C 
code instead of LINE B then it compiles alright, but if I try to run the 
R script it says:

Error in FUN(c("Rc", "Rc2")[[1]], ...) : no such symbol Rc in package C:/Documents and Settings/Toby/Desktop/cfiles/Project1.exe

I've read a lot online about the "R CMD INSTALL" command and the 
?INSTALL man page, but I can't use that command because I've got 
Windows-R rather than Linux-R (unfortunately). Somehow, R can't 'see' 
these C functions in the executable, even though I thought including 
Rinternals.h ensured that it could. Stuck.

Additionally, if I have LINE B instead of LINE A in the C code then it 
won't compile at all and gives the errors:

[Linker error] Unresolved external '_REAL' referenced from C:\DOCUMENTS AND SETTINGS\TOBY\DESKTOP\CFILES\SIMPLECALL.OBJ
[Linker error] Unresolved external '_Rf_ScalarReal' referenced from C:\DOCUMENTS AND SETTINGS\TOBY\DESKTOP\CFILES\SIMPLECALL.OBJ

which I find odd because these symbols are defined in the .h files included at the start.

I feel like I'm either a) trying to do this in completely the wrong way or b) suffering from having to use a Windows machine or c) both. I tried setting up a package and inserting the code in the /src directory, but because I can't use the R CMD INSTALL command I can't figure out how to make this idea work either.

Can anyone help me here? Does anyone have an actual example of something like this that works?

Toby Marthews

?..?????`????..?????`??..?????`?.?????`??..?????`??..?????`?.?

Institut f?r Umweltwissenschaften (IfU, www.uzh.ch/uwinst <http://www.uzh.ch/uwinst> ),
Universit?t Z?rich, Winterthurerstr. 190, 8057 Z?rich, CH.

Plant & Soil Science Department (www.abdn.ac.uk/biologicalsci/pss <http://www.abdn.ac.uk/biologicalsci/pss> ),
University of Aberdeen, 23 St Machar Dr., Aberdeen AB24 3UU, UK.

?`??..?????`?.?????`??..?????`??..?????`?.? ><(((?> ?.???`?..? ><(((?>

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