So you can’t use them then.

I don't think it would be typical to depend on exception handling when dealing with boundary conditions with C++ containers.

I mean .at is great and all, but it's really for the benefit of eliminating undefined behavior and if the program just terminates then you've achieved this. I've seen decoders that just catch the std::out_of_range or even std::exception to handle the remaining bugs in the logic, though.