I agree with the other comments that this understanding of exceptions is wrong. He's not wrong about these two points:

- Correctness: you don’t know if the exception type you’ve caught matches what the code throws

- Exhaustiveness: you don’t know if you’ve caught all exceptions the code can throw

But that's actually not a problem. Most of the time you shouldn't catch a specific exception (so always correct) and if you are catching then you should catch them all (exhaustive). A better solution is merely:

    void f(string s)
    {
        try {
            File_handle fh { s, "r"};
            // use fh
        } catch (const std::exception& e) {
            printf(stderr, e.what());
        }
    }

That's all you need. But actually this code is also bad because this function f() shouldn't have a try/catch in it that prints an error message. That's a job for a function (possibly main()) further up the call stack.