Your attention is invited to the sixth part of an e-book on undefined behavior. This is not a textbook, as it's intended for those who are already familiar with C++ programming. It's a kind of C++ programmer's guide to undefined behavior and to its most secret and exotic corners. The book was written by Dmitry Sviridkin and edited by Andrey Karpov.

C++ programmer's guide to undefined behavior: part 6 of 11

by Dmitry Sviridkin

From the article:

I/O streams have other flags that represent the state of the stream: whether there were errors, whether we reached the end. Many people know that you can check whether an operation was successful by putting a stream object into a conditional statement (or any context where it is converted to bool). Those unfamiliar with it might use the while (!iss.eof()) check that will one day lead to the infinite loop issue. This happens when the file isn't finished, but can no longer be read—say, if the file is on a network drive, and the network has gone down. Well, that's a story for another time. Let's focus on the correct way to check readability.