Hi again,
On Wed, 22 Jan 2014 06:39:17 -0600
Dirk Eddelbuettel <edd at debian.org> wrote:
| Working examples I know of:
|
| 'xts' importing two functions from 'zoo'
|
| 'RcppXts' importing approx. ten functions from 'xts'
|
| Maybe by comparing to these you can sort out the missing step at your end.
Thanks Dirk for the hints; I finally got the code running. Important point
is that R_init_PKGNAME() is declared as extern "C" (or RcppExport, of course)
if using g++ in both the mother and the child package. (Interestingly,
dyn.load() only complains when either the mother or the child package don't
do so, but not if both don't do so => SEGFAULT.) Since it took me almost the
entire afternoon to figure that out, I'll document a working example here.
Scenario: We have a 'mother' package, which wants to make some C/C++ routines
available to the 'child' package to be called directly from C/C++ level.
Thus, mother's 'src' cointains:
********* BEGIN test.c *********
#include <R.h>
#include <Rinternals.h>
#include <R_ext/Rdynload.h>
SEXP fun(SEXP);
void R_init_mother(DllInfo *dll) {
R_RegisterCCallable("mother", "fun", (DL_FUNC) &fun);
}
SEXP fun(SEXP test) {
Rprintf("fun so much fun\n");
return R_NilValue;
}
********** END test.c **********
(Note that no extern "C" is needed here because it will be compiled with gcc
anyway).
The child uses Rcpp and mother, thus has
********* BEGIN DESCRIPTION *********
LinkingTo: mother, Rcpp
Depends: mother, Rcpp
Imports: mother, Rcpp
********** END DESCRIPTION **********
in its DESCRIPTION file, and
********* BEGIN test.cpp *********
#include <Rinternals.h>
#include <R_ext/Rdynload.h>
extern "C" {
SEXP afun(SEXP);
SEXP(*fun)(SEXP);
void R_init_child(DllInfo *info) {
fun = (SEXP(*)(SEXP)) R_GetCCallable("mother", "fun");
}
SEXP afun(SEXP test) {
fun(test);
return R_NilValue;
}
}
********** END test.cpp **********
(Note that extern "C" is crucial here.) After installing mother and child, we
have:
Loading required package: mother
Loading required package: Rcpp
.Call("afun", 123, PACKAGE="child")
Maybe it is of help to someone; please excuse me if I bored anyone with
trivialities.
Best,
Gregor