Function luaV_finishget

3rd/lua-5.4.3/src/lvm.c:287–320

** Finish the table access 'val = t[key]'. ** if 'slot' is NULL, 't' is not a table; otherwise, 'slot' points to ** t[k] entry (which must be empty). */

** t[k] entry (which must be empty).
*/
void luaV_finishget (lua_State *L, const TValue *t, TValue *key, StkId val,
                      const TValue *slot) {
  int loop;  /* counter to avoid infinite loops */
  const TValue *tm;  /* metamethod */
  for (loop = 0; loop < MAXTAGLOOP; loop++) {
    if (slot == NULL) {  /* 't' is not a table? */
      lua_assert(!ttistable(t));
      tm = luaT_gettmbyobj(L, t, TM_INDEX);
      if (l_unlikely(notm(tm)))
        luaG_typeerror(L, t, "index");  /* no metamethod */
      /* else will try the metamethod */
    }
    else {  /* 't' is a table */
      lua_assert(isempty(slot));
      tm = fasttm(L, hvalue(t)->metatable, TM_INDEX);  /* table's metamethod */
      if (tm == NULL) {  /* no metamethod? */
        setnilvalue(s2v(val));  /* result is nil */
        return;
      }
      /* else will try the metamethod */
    }
    if (ttisfunction(tm)) {  /* is metamethod a function? */
      luaT_callTMres(L, tm, t, key, val);  /* call it */
      return;
    }
    t = tm;  /* else try to access 'tm[key]' */
    if (luaV_fastget(L, t, key, slot, luaH_get)) {  /* fast track? */
      setobj2s(L, val, slot);  /* done */
      return;
    }
    /* else repeat (tail call 'luaV_finishget') */
  }
  luaG_runerror(L, "'__index' chain too long; possible loop");
}


/*