The behaviour of signed integer overflow is undefined, but only if it actually overflows, and whether it overflows or not can be based on the widths of types wh

The behaviour of signed integer overflow is undefined, but only if it actually overflows, and whether it overflows or not can be based on the widths of types which are implementation-defined, so there is a link between the two things. Many "correct" programs rely on undefined behaviour for optimizations while the authors knowingly assert (or assume) that the undefined behaviour doesn't actually occur. So the question is, if you are writing non-portable code for a specific environment, is a UB that actually triggers on your environment "non-portability" or is it a "bug"? I think most people would define that as being a bug. Edit: Okay, bad example cos you could maybe use int_leastN_t or something in that example to document the assumptions... But you don't always have control over types, and there may be multiple constraints, etc..