error handling in recursive function.

This is a discussion on error handling in recursive function. within the C Programming forums, part of the General Programming Boards category; hello can some one please explain me how to do error handling in a recursive function. for eg. the following ...

  1. #1
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    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.

  2. #2
    C++まいる!Cをこわせ! Elysia's Avatar
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    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.
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  3. #3
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    Quote Originally Posted by Elysia View Post
    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() ;

  4. #4
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by broli86 View Post
    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.

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    Quote Originally Posted by tabstop View Post
    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);

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