Thread: error handling in recursive function.

hello can some one please explain me how to do error handling in a recursive function. for eg. the following is a recursive function :

Code:

void subdivide_kdtree(kdnode *kd, mesh *m, int depth, int maxdepth, int maxtriangles, int axis)
{
  int i, nextaxis;
  kd->child[0] = kd->child[1] = NULL;
  trinode *ptr, *last;
   
  if(kd->ntriangles > maxtriangles && depth < maxdepth)
  {
    for(i = 0; i < 2; i++)
    {
      kd->child[i] = malloc(sizeof(kdnode));
      kd->child[i]->box = kd->box;
      kd->child[i]->trifirst = NULL;
      kd->child[i]->ntriangles = 0;
      kd->splitplane = axis;
      kd->child[i]->box.minB.coord[axis] = kd->box.minB.coord[axis] + 0.5 * i * (kd->box.maxB.coord[axis] - kd->box.minB.coord[axis]);
      kd->child[i]->box.maxB.coord[axis] = kd->box.minB.coord[axis] + 0.5 * (i+1) * (kd->box.maxB.coord[axis] - kd->box.minB.coord[axis]);
      nextaxis = (axis + 1) &#37; 3;      
      ptr = kd->trifirst;
      while(ptr != NULL)
      {
        if(insidebox(kd->child[i], m, ptr->tindex, axis, i))
        {
          add_to_triangle_list(&kd->child[i]->trifirst, &last, ptr->tindex);
          kd->child[i]->ntriangles += 1;
        }
        ptr = ptr->next;
      }
      subdivide(kd->child[i], m, depth + 1, maxdepth, maxtriangles, nextaxis);
    }
  }
}

Notice the bolded part. If malloc fails I usually do error handlling by passing a flag which indicates an error has happened and i also print an error message. just for the sake of an example:

Code:

int some_function(void)
{
   double *p;
    int flag = 0;

   p = malloc(sizeof(*p) * 500);
   if(p == NULL)
  {
    fprintf(stderr, "\n%s line %d : Memory allocation failure\n", __FILE__, __LINE__);
    flag = 1;
    return flag;
  }

  return flag;
}

I mean how to pass this flag in a recursive function is what i can't figure out. pls help me out.

Originally Posted by Elysia

Since a recursive function typically keeps returning what it returns after calling itself, you can just return an error flag. Ie:

malloc(...);
if (error)
return error_flag;
return myfunction(...);

The entire chain will then return your error flag.

can you please elaborate this statement:

return myfunction() ;

Originally Posted by broli86

can you please elaborate this statement:

return myfunction() ;

That's your recursive call. Obviously you'd need to fill in the () bit with n/2 or n-1 or whatever.

Originally Posted by tabstop

That's your recursive call. Obviously you'd need to fill in the () bit with n/2 or n-1 or whatever.

yeah basically the arguments of the recursive function.

return myfunction(arg1, arg2, arg3);