luaC_barrierback
luaC_barrierback(L, gcvalue(t), L->top-1);
luaC_barrierback(L, gcvalue(t), L->top-1);
luaC_barrierback(L, gcvalue(t), L->top - 1);
luaC_barrierback(L, obj2gco(t), key);
luaC_barrierback(L, obj2gco(h), val);
luaC_barrierback(L, obj2gco(h), val);