LPEG strange code

[Domingo Alvarez Duarte <mingodad@...>]

Hello !

I'm trying to port lpeg 1.0.1 to another scripting language and doing so 
I'm going through almost all lpeg code and of course I'm making several 
mistakes while porting.

But on one of many segfaults I've got I stumbled at this code in 
lptree.c (the order of the functions was altered here to show then in 
call order), it seems that this code was a copy/paste leftover or some 
code from trying different approaches and forgotten here.

It seems a kind of weird assert !

Thanks for your time, attention and great work !

...

/*
** Create a new 'ktable' to the pattern at the top of the stack, adding
** all elements from pattern 'p' (if not 0) plus element 'idx' to it.
** Return index of new element.
*/
static int addtonewktable (lua_State *L, int p, int idx) {
  newktable(L, 1);
  if (p)
    mergektable(L, p, NULL); ////// <<<<<< Here we are calling 
mergektable with a NULL !!!!!
  return addtoktable(L, idx);
}

...

/*
** merge 'ktable' from 'stree' at stack index 'idx' into 'ktable'
** from tree at the top of the stack, and correct corresponding
** tree.
*/
static void mergektable (lua_State *L, int idx, TTree *stree) { //// <<< 
when called with stree=NULL !!!!
  int n;
  lua_getuservalue(L, -1);  /* get ktables */
  lua_getuservalue(L, idx);
  n = concattable(L, -1, -2);
  lua_pop(L, 2);  /* remove both ktables */
  correctkeys(stree, n); ///<<<<< Here we'll segfault !!!!!!
}
...

/*
** When joining 'ktables', constants from one of the subpatterns must
** be renumbered; 'correctkeys' corrects their indices (adding 'n'
** to each of them)
*/
static void correctkeys (TTree *tree, int n) { ///<<<< When tree is NULL 
and n is not zero
  if (n == 0) return;  /* no correction? */
 tailcall:
  switch (tree->tag) { ///<<<<<<   Here we'll segfault !!!!!!! <<<<<<< 
!!!!!!!!!<<<<<<<< !!!!
    case TOpenCall: case TCall: case TRunTime: case TRule: {
      if (tree->key > 0)
        tree->key += n;
      break;
    }
    case TCapture: {
      if (tree->key > 0 && tree->cap != Carg && tree->cap != Cnum)
        tree->key += n;
      break;
    }
    default: break;
  }
  switch (numsiblings[tree->tag]) {
    case 1:  /* correctkeys(sib1(tree), n); */
      tree = sib1(tree); goto tailcall;
    case 2:
      correctkeys(sib1(tree), n);
      tree = sib2(tree); goto tailcall;  /* correctkeys(sib2(tree), n); */
    default: assert(numsiblings[tree->tag] == 0); break;
  }
}