From: Peter Zijlstra > Sent: 17 April 2021 12:17 ... > > (i'd argue this is C being broken; promoting only as far as int, when > > assigning to an unsigned long is Bad, but until/unless either GCC fixes > > that or the language committee realises that being stuck in the 1970s > > is Bad, people are going to keep making this kind of mistake) > > Well, I think the rules actually make sense, at the point in the syntax > tree where + happens, we have 'unsigned char' and 'int', so at that > point we promote to 'int'. Subsequently 'int' gets shifted and bad > things happen. The 1970s were fine. K&R C was sign preserving - so 'unsigned char' promoted to 'unsigned int'. The ANSI C committee broke things by changing it to value preserving with the strong preference for signed types. Even with ANSI C the type of ((unsigned char)x + 1) can be unsigned! All it needs as an architecture where sizeof (int) == 1. (sizeof (char) has to be 1 - even though that isn't directly explicit.) Of course, having 32-bit 'char' and 'int' does give problems with the value for EOF. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
