Path: ...!feed.opticnetworks.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Tim Rentsch Newsgroups: comp.lang.c Subject: Re: "undefined behavior"? Date: Sat, 22 Jun 2024 09:28:14 -0700 Organization: A noiseless patient Spider Lines: 39 Message-ID: <86cyo9gcwx.fsf@linuxsc.com> References: <666a095a$0$952$882e4bbb@reader.netnews.com> <877cet7qkl.fsf@nosuchdomain.example.com> <86frt9ixw2.fsf@linuxsc.com> <87y171yd87.fsf@nosuchdomain.example.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Date: Sat, 22 Jun 2024 18:28:16 +0200 (CEST) Injection-Info: dont-email.me; posting-host="ec2cba2faddfc9625d8883c2f98b569e"; logging-data="4039421"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18/JH8tKA0eTJ9oXkrvo6AxKDH6OjaBmQk=" User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.4 (gnu/linux) Cancel-Lock: sha1:I3WEBbAMfUBvk6sx4vYTamjmX4w= sha1:9wnMNmuOzBKed6NZ5Jll0Ty8ODc= Bytes: 2699 Keith Thompson writes: > Tim Rentsch writes: > >> Keith Thompson writes: >> >>> (I'd like to a future standard require plain char to be unsigned, >>> but I don't know how likely that is.) >> >> It seems unnecessary given that the upcoming C standard >> is choosing to mandate two's complement for all signed >> integer types. > > It's less necessary, but I'd still like to see it. > > These days, strings very commonly hold UTF-8 data. The fact that bytes > whose values exceed 127 are negative is conceptually awkward, even if > everything happens to work. It rarely if ever makes sense to treat a > character value as negative. The combination of mandating two's complement and using a compiler option like -funsigned-char (supported by both gcc and clang) should be enough to do what you want. > (And of course signed char still exists, > or int8_t if you prefer 8 bits vs. CHAR_BIT bits.) It makes me laugh when people use int8_t instead of signed char. If CHAR_BIT isn't 8 then there won't be any int8_t. And of course we can always throw in a static assertion if it is felt necessary to protect against implementations that don't have 8-bit chars. (A static assertion also can verify that two's complement is being used for signed char.) > A drawback is that it could break existing (non-portable) code that > assumes plain char is signed. Exactly! No reason to break the whole world when you can get what you want just by using a compiler option.