Rcpp with armadillo

arma_by_reference.cpp

// advanced constructor 
// mat(ptr_aux_mem, n_rows, n_cols, copy_aux_mem = true, strict = false)


#include <RcppArmadillo.h>
#include <Rcpp.h>

// Pass by reference, readonly
arma::mat testmx( const arma::mat& dat)
{
  return dat;
}


// Pass by reference, can be modified
arma::mat testmx2(arma::mat& dat)
{
  return dat;
}

RcppExports.cpp

arma::mat testmx(const arma::mat& dat);
RcppExport SEXP _testmx(SEXP datSEXP) {
BEGIN_RCPP
    Rcpp::RObject rcpp_result_gen;
    Rcpp::RNGScope rcpp_rngScope_gen;
    Rcpp::traits::input_parameter< const arma::mat& >::type dat(datSEXP);
    rcpp_result_gen = Rcpp::wrap(testmx(dat));
    return rcpp_result_gen;
END_RCPP
}

arma::mat testmx2(arma::mat& dat);
RcppExport SEXP _testmx2(SEXP datSEXP) {
BEGIN_RCPP
    Rcpp::RObject rcpp_result_gen;
    Rcpp::RNGScope rcpp_rngScope_gen;
    Rcpp::traits::input_parameter< arma::mat& >::type dat(datSEXP);
    rcpp_result_gen = Rcpp::wrap(testmx2(dat));
    return rcpp_result_gen;
END_RCPP
}

Rcpp takes care of the memory management by wrapping the arrays accordingly.