At what point in the loop does integer overflow become undefined behavior?

Question

This is an example to illustrate my question which involves some much more complicated code that I can\'t post here.

#include 
int main()
{
           


        

Answer 1

Undefined behavior is, by definition, a grey area. You simply can't predict what it will or won't do -- that's what "undefined behavior" means.

Since time immemorial, programmers have always tried to salvage remnants of definedness from an undefined situation. They've got some code they really want to use, but which turns out to be undefined, so they try to argue: "I know it's undefined, but surely it will, at worst, do this or this; it will never do that." And sometimes these arguments are more or less right -- but often, they're wrong. And as the compilers get smarter and smarter (or, some people might say, sneakier and sneakier), the boundaries of the question keep changing.

So really, if you want to write code that's guaranteed to work, and that will keep working for a long time, there's only one choice: avoid ye the undefined behavior at all costs. Verily, if you dabble in it, it will come back to haunt you.