I have a function with the following form :

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

// [[Rcpp::plugins(openmp)]]
#include <omp.h>

// [[Rcpp::depends(RcppParallel)]]
#include <RcppParallel.h>

using namespace Rcpp;
using namespace std;

NumericVector parallel_Calculation(Function &FUN,
                                   const NumericVector &param)
{
  ...

  #pragma omp parallel for 
  for(int k = 0; k < nb_Param; k++)
  {
     /* Using the FUN function to perform calculations */
  }

  ...
}

I would like to use an arbitrary function defined in R in a parallel Rcpp code. First, is the variable FUN thread-safe? If not, is there a way to make it thread safe?