Compiling multiple source files in Rcpp - c++

Question

I have the following directory structure
my_func
- my_func_r.cpp
- my_func.c
- my_func.h
- my_func_test.c
- matrix/
- matrix.h
- matrix.c
The matrix directory contains some matrix structures in matrix.h and some initialisation, free, print etc. functions in matrix.c. The my_func.h file is something like
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "matrix/matrix.h"
... some structures and templates ...
The my_func.c file is then
#include "my_func.h"
... helper functions ...
int my_func(...) {
... my_func stuff ...
return 0;
}
The my_func_test.c is something like
#include "my_func.h"
int main() {
... some test ...
return 0;
}
With gcc/g++ I can run this fine with
gcc my_func_test.c my_func.c matrix/matrix.c -o test -lm
The final file my_func_r.cpp is an interface between the Rcpp structures and the structures used in my_func.c. It is currently something like
#include "my_func.h"
#include <Rcpp.h>
// [[Rcpp::export]]
int my_func_r(Rcpp::List x, ...) {
... convert inputs to structure recognised by my_func.h ...
... run my_func.c ...
... put returned objects back into one of the R structure ...
return 0;
}
The problem I have is if I now run
sourceCpp('my_func_r.cpp', verbose=TRUE, rebuild=TRUE)
It complains about missing symbols for functions located in matrix/matrix.c. A workaround is to simply paste all my header and source code from both the my_func and matrix files at the top of my_func_r.cpp.
This however feels a very unsatisfactory solution especially for code maintenance. What is the easiest way to accomplish what I am trying to do?

Answer 1

Quick ones:
This is not really particular to Rcpp per se
You are simply struggling with a more advanced / complicated src/ directory in an R build.
There is official documentation about this in Writing R Extensions, and the questions has come up here on SO before.
You could compile a libmatrix.a first in the subdirectory and link to that. This is doable via a simple src/Makevars but still discouraged. So read on.
But this is a self-inflicted wound. Just copy matrix.h and matrix.c into src/, adjust the include path, and you are done.
As always: Create a package. Don't use sourceCpp() on larger setup. It is not made for that,