Oliver Kullmann wrote:
Sure, for the language lawyers. But my point here is to argue that it is NOT POSSIBLE to read integers in C++ from an input stream without running into undefined behaviour (if we do not have perfect control over the size of numbers), and w.r.t. this the C90 standard is just worse than the C99 standard.
It simply leaves this question not-standarized and the C++ standard does not add anything in this respect.
The only difference between "not-standardized" and "undefined behaviour" is, that in the latter case we are at least conscious about it, while in the former case we have no clue (and closing the eyes before a problem doesn't usually solve the problem).
No at all. If you were right, then we would have been unable to write multithreaded programs, programs that use dynamic libraries etc. - because these isues are left out of standard (C++ and C). The fact is that when something is left out of standard, it is actually left to implementor. The very issue you are rising here has been actually discussed by the C++ standard committee and conclusion was that currently there is no risk of UB. There are worse problems to solve, eg: int main() { int a, b; std::cin >> a >> b; int c = a * b; // potential UB here } B.