Or they assume "param + 16" will never overflow, so they emit an ADD instruction and use whatever result it yields. Saying that a compiler "assumes" anything i

Or they assume "param + 16" will never overflow, so they emit an ADD instruction and use whatever result it yields. Saying that a compiler "assumes" anything is anthropomorphic. A compiler may behave (generate code) in a manner that does not take the presence or absence of undefined behavior into account. If you just say it assumes something, that doesn't tell you what it will do based on that assumption. Generating code that yields exactly 16 iterations is one of infinitely many possible consequences of undefined behavior. If the mathematical value of `param + 16` exceeds `INT_MAX`, then the code has undefined behavior. The C standard says nothing at all about how the program will behave. A conforming compiler can generate code that iterates 42 times and then whistles Dixie. The non-normative note under the definition of "undefined behavior" does not constrain what a conforming implementation is allowed to do. "imposes no requirements" means "imposes no requirements".