http://stackoverflow.com/questions/42261822/c-interface-with-rcppinterfaces-not-working-for-a-function-returning-stdpa/42287094#42287094

hinterface.cpp

// src/hinterface.cpp
#include "hinterface.h"

// [[Rcpp::export]]
int call_bla_in_hinterface()
{ return hinterface::bla().first; }

// [[Rcpp::export("bla")]]
void bla_()
{
    std::pair<int, int> x = hinterface::bla();
    std::printf(
        "x.first = %d\nx.second = %d\n",
        x.first, x.second
    );
}