Function lua_settop

extlibs/lua/src/lapi.c:172–191

LUA_API void lua_settop (lua_State *L, int idx) {
  CallInfo *ci = L->ci;
  StkId func = ci->func;
  ptrdiff_t diff;  /* difference for new top */
  lua_lock(L);
  if (idx >= 0) {
    api_check(L, idx <= ci->top - (func + 1), "new top too large");
    diff = ((func + 1) + idx) - L->top;
    for (; diff > 0; diff--)
      setnilvalue(s2v(L->top++));  /* clear new slots */
  }
  else {
    api_check(L, -(idx+1) <= (L->top - (func + 1)), "invalid new top");
    diff = idx + 1;  /* will "subtract" index (as it is negative) */
  }
  if (diff < 0 && hastocloseCfunc(ci->nresults))
    luaF_close(L, L->top + diff, LUA_OK);
  L->top += diff;  /* correct top only after closing any upvalue */
  lua_unlock(L);
}


/*