choose m random numbers between 1-n

How would you choose m random numbers between 1-n

void genM(int m,int n)
{
int *x = new  int[n+1];
 for(i =0;i<=n;i++)
      x[i] = i;
 for(i = 1; i<=m; i++)
 {
     j = randint(i, n);
     swap(x[i],x[j]);
} 
 for(i = 1;i<=m;i++)
      std::cout << x[i]<< std::endl;
}