Hi! On Fri, Jul 18, 2025 at 07:11:12PM +0200, David Brown wrote: > I'm getting the feeling that we've got our wires crossed somewhere. > > Signed integer /arithmetic/ overflow is UB in the C standards and in gcc > (unless "-fwrapv" is in effect). Yup. > Conversion to a signed integer type, when the value cannot be preserved, is > implementation-defined behaviour in the C standards, and in gcc (gcc defines > it to be two's complement wrapping). And leaving it UB is a valid implementation. An implementation is not required to specify anything in particular. > A "cast from unsigned to int" is a conversion, thus it is > implementation-defined. Yup. > I think somewhere along the line in this thread, the conversions and signed > integer arithmetic overflows have been mixed together. Oh, people do that all the time! Segher
