c++ - What is cause of segmentation fault here? -

i have written small array merge procedure. on running getting segmentation fault. can point out me have gone wrong here?

#include <iostream>  using namespace std;  void merge(int arr[], int p, int q, int r) {     int l[q-p+1];     int r[r-q];      for(int = p; < r;i++)     {         if(i<q+1)         {             l[i] = arr[i];         }         else         {             r[i-q+1] = arr[i];         }     }      int = 0, j = 0,k = p;      while(i<q-p+1 || j<r-q)     {         if(l[i]>r[j])         {             arr[k] = r[j];             j++;         }         else         {             arr[k] = l[i];             i++;         }          k++;     }      if(i == q-p+1)     {         for(;j<r-q;j++,k++)         {             arr[k] = r[j];         }     }      if(j == r-q)     {         for(;i<q-p+1;i++,k++)         {             arr[k] = l[i];         }     } }  int main() {     cout << "hello world!" << endl;     int a[] = {2,4,6,8,1,3,5,9};     merge(a,0,3,7);      for(int = 0; i<8;i++)     {         cout<<a[i]<<"\t";     }     return 0; } 

you should step through in debugger.

this line of code:

while (i<q - p + 1 || j<r - q) 

will not prevent being >= q-p+1 (i.e if j still less r-q). mean reading outside of array boundaries.

you should change to

while (i<q - p + 1 && j<r - q) 

also note: int l[q-p+1] not valid c++, valid c, not c++