Why does integer overflow cause errors with C++ iostreams?

Question

Ok, so I have some problems with C++ iostreams that feels very odd, but it is probably defined behaviour, considering this happens with both MSVC++ and G++.

Say I ha

Answer 1

a starts out with an undefined value. It's not cin's fault. Try:

if (cin >> a) {
  cout << a endl;
}

It will check whether the read into a succeeded before using a