[R] interfacing C++ using .Call

Sundar Dorai-Raj sundar.dorai-raj at pdf.com
Tue Feb 17 16:24:15 CET 2004

Hi folks,
   I apologise if this is in the documentation somewhere, but I can't 
seem to find it. I also did a search of CRAN without any success. I'm 
using R-1.8.1 (pre-compiled) on Windows 2000 with Rtools and mingw 2.0.0 
(which includes gcc/g++ 3.2).

I'm trying to link some C++ code from another application to R using the 
.Call interface and am experiencing some problems. I was able to compile 
and link the example from Section 4.6 in R-exts.pdf without any 
difficulty. But if I take a more complicated example that uses SEXP I'm 
able to compile but not link. Here's an example:

Take the "lapply2" code on page 49 of R-exts.pdf and save to "test.c". 
Be sure to add

#include <R.h>
#include <Rdefines.h>

to the top of the file.

Now at the command line type:

 > Rcmd SHLIB test.c
making test.d from test.c
gcc   -Id:/R/rw1081/src/include -Wall -O2   -c test.c -o test.o
ar cr test.a *.o
ranlib test.a
gcc  --shared -s  -o test.dll test.def test.a 
-Ld:/R/rw1081/src/gnuwin32  -lg2c -lR

Works fine (though I haven't tested in R but at least the dll is 
created). Now remove all files except "test.c" and rename to "test.cpp".

 > Rcmd SHLIB test.cpp
making test.d from test.cpp
g++   -Id:/R/rw1081/src/include -Wall -O2   -c test.cpp -o test.o
ar cr test.a *.o
ranlib test.a
g++  --shared -s  -o test.dll test.def test.a 
-Ld:/R/rw1081/src/gnuwin32  -lg2c -lR
test.a(test.o.b)(.text+0x61):test.cpp: undefined reference to 
test.a(test.o.b)(.text+0x6e):test.cpp: undefined reference to 
test.a(test.o.b)(.text+0x82):test.cpp: undefined reference to 
test.a(test.o.b)(.text+0x99):test.cpp: undefined reference to 
test.a(test.o.b)(.text+0xb7):test.cpp: undefined reference to 
`Rf_lang2(SEXPREC*, SEXPREC*)'
test.a(test.o.b)(.text+0xc2):test.cpp: undefined reference to 
test.a(test.o.b)(.text+0xcf):test.cpp: undefined reference to 
`Rf_allocVector(unsigned, int)'
test.a(test.o.b)(.text+0xda):test.cpp: undefined reference to 
test.a(test.o.b)(.text+0xf5):test.cpp: undefined reference to 
`Rf_getAttrib(SEXPREC*, SEXPREC*)'
test.a(test.o.b)(.text+0x107):test.cpp: undefined reference to 
test.a(test.o.b)(.text+0x113):test.cpp: undefined reference to 
test.a(test.o.b)(.text+0x129):test.cpp: undefined reference to 
test.a(test.o.b)(.text+0x132):test.cpp: undefined reference to 
test.a(test.o.b)(.text+0x13e):test.cpp: undefined reference to 
test.a(test.o.b)(.text+0x14a):test.cpp: undefined reference to 
make: *** [test.dll] Error 1

Adding extern "C" {} does not help the problem. Can anybody replicate 
this? Is there something I'm missing?


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