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Received: from SV0P279MB0233.NORP279.PROD.OUTLOOK.COM (2603:10a6:f10:b::13) by OS5P279MB0761.NORP279.PROD.OUTLOOK.COM (2603:10a6:e10:40::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6954.19; Thu, 2 Nov 2023 09:24:11 +0000 Received: from SV0P279MB0233.NORP279.PROD.OUTLOOK.COM ([fe80::284b:5363:e5d9:dc73]) by SV0P279MB0233.NORP279.PROD.OUTLOOK.COM ([fe80::284b:5363:e5d9:dc73%3]) with mapi id 15.20.6954.021; Thu, 2 Nov 2023 09:24:11 +0000 Message-ID: <0d8b9274-737b-94cf-9849-ad30cc63df6b@westcontrol.com> Date: Thu, 2 Nov 2023 10:24:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: Suboptimal warning formatting with `bool` type in C Content-Language: en-GB To: peter0x44 , Joseph Myers Cc: Gcc References: <586ce4ef-2760-3f79-627e-ca34e345319d@codesourcery.com> <288ea19452236f82f8f145f9b15e6335@disroot.org> From: David Brown In-Reply-To: <288ea19452236f82f8f145f9b15e6335@disroot.org> Content-Type: text/plain; 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I can't imagine how this could >>> possibly break any existing code. >> >> That's how stdbool.h is specified up to C17.  In C23, bool is a keyword >> instead. > > I see, I didn't know it was specified that way. It seems quite strange > that typedef wouldn't be used for this purpose. > > I suppose perhaps it matters if you #undef bool and then use it to > define your own type? Still, it seems very strange to do this. > Yes, that is part of the reason. The C standards mandate a number of things to be macros when it would seem that typedef's, functions, enumeration constants or other things would be "nicer" in some sense. Macros have two advantages, however - you can "#undef" them, and you can use "#ifdef" to test for them. This makes them useful in several cases in the C standards, especially for changes that could break backwards compatibility. Someone writing /new/ code would hopefully never make their own "bool" type, but there's plenty of old code around - if you ever need to include some pre-C99 headers with their own "bool" type and post-C99 headers using , within the same C file, then it's entirely possible that you'll be glad "bool" is a macro. > Maybe it's something to offer as a GNU extension? Though, I'm leaning > towards too trivial to be worth it, just for a (very minor) improvement > to a diagnostic that can probably be handled in other ways. > Speaking as someone with absolutely zero authority (I'm a GCC user, not a GCC developer), I strongly doubt that "bool" will be made a typedef as a GCC extension. But if there are problems with the interaction between pre-processor macros and the formatting of diagnostic messages, then that is definitely something that you should file as a bug report and which can hopefully be fixed. David