caught segfault, memory not mapped error in Rcpp trying to implement a function

问题

i'm new in Rcpp and i dont really know Rcpp. but as a personal project, i was trying to run some sort algorithms using some C code that i had, converting them to R with Rcpp.

But i'm getting the memory not mapped error, and i dont really understand what i'm doing wrong, so if someone could enlighten me :)

The problem happens when a try the following code

#include <Rcpp.h>
using namespace Rcpp;

void intercala(int p, int q, int r, NumericVector v)
{
  int i, j, k;
  NumericVector w = NumericVector::create();

   i = p;
   j = q;
   k = 0;


   while (i < q && j < r) {
      if (v[i] < v[j]) {
         w[k] = v[i];
         i++;
      }
      else {
         w[k] = v[j];
         j++;
      }
      k++;
   }
   while (i < q) {
      w[k] = v[i];
      i++;
      k++;
   }
   while (j < r) {
      w[k] = v[j];
      j++;
      k++;
   }
   for (i = p; i < r; i++)
      v[i] = w[i-p];
}

void mergesort(int p, int r, NumericVector v)
{
   int q;
   if (p < r - 1) {
      q = (p + r) / 2;
      mergesort(p, q, v);
      mergesort(q, r, v);
      intercala(p, q, r, v);
   }
}

// [[Rcpp::export]]
NumericVector mergesortC(NumericVector vetor) {
  int n = vetor.size();
  mergesort(0,n,vetor);
  return vetor;
}

This code is in a file called merge.cpp

Them when i try to run on R

    > library(Rcpp)
    > sourceCpp("merge.cpp")
    > vetor<-sample(1:10)
    > vetor
     [1]  1  5  7  4  3  8  9  2 10  6
    > mergesortC(vetor)
     [1]  1  2  3  4  5  6  7  8  9 10
    > vetor

     *** caught segfault ***
    address 0x8, cause 'memory not mapped'

    Possible actions:
    1: abort (with core dump, if enabled)
    2: normal R exit
    3: exit R without saving workspace
    4: exit R saving workspace
    Selection:

It seems to me that i'm doing something that i shouldn't, but the code seem to work in the begin, then i somehow mess with the memory in the object vetor. I managed to work on other algorithms with Rcpp, but this one wont work, and i dont understand what i'm doing wrong, so if anyone could spare a moment.

来源：https://stackoverflow.com/questions/25633615/caught-segfault-memory-not-mapped-error-in-rcpp-trying-to-implement-a-function

标签

mergesort

rcpp