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

Assuming int is 32-bit, undefined behavior happens at the third iteration. So if, for example, the loop was only conditionally reachable, or could conditionally be terminated before the third iteration, there would be no undefined behavior unless the third iteration is actually reached. However, in the event of undefined behavior, all output of the program is undefined, including output which is "in the past" relative to the invocation of undefined behavior. For example, in your case, this means there is no guarantee of seeing 3 "Hello" messages in the output.