C++ runtime exception with implement of MNIST

I copied the code on the official site: https://pytorch.org/cppdocs/frontend.html and have the same path problem in this line:
auto data_loader = torch::data::make_data_loader(torch::data::datasets::MNIST("./data").map(torch::data::transforms::Stack<>()),/batch_size=/64);
it is similar to the following problem:
Running error with libtorch C++ front
Does anybody have the same problem? How to solve it?