Function lua_setmetatable

deps/lua/src/lapi.c:697–731

LUA_API int lua_setmetatable (lua_State *L, int objindex) {
  TValue *obj;
  Table *mt;
  lua_lock(L);
  api_checknelems(L, 1);
  obj = index2adr(L, objindex);
  api_checkvalidindex(L, obj);
  if (ttisnil(L->top - 1))
    mt = NULL;
  else {
    api_check(L, ttistable(L->top - 1));
    mt = hvalue(L->top - 1);
  }
  switch (ttype(obj)) {
    case LUA_TTABLE: {
      hvalue(obj)->metatable = mt;
      if (mt)
        luaC_objbarriert(L, hvalue(obj), mt);
      break;
    }
    case LUA_TUSERDATA: {
      uvalue(obj)->metatable = mt;
      if (mt)
        luaC_objbarrier(L, rawuvalue(obj), mt);
      break;
    }
    default: {
      G(L)->mt[ttype(obj)] = mt;
      break;
    }
  }
  L->top--;
  lua_unlock(L);
  return 1;
}


LUA_API int lua_setfenv (lua_State *L, int idx) {