Path: csiph.com!aioe.org!eternal-september.org!reader01.eternal-september.org!.POSTED!not-for-mail From: Tim Rentsch Newsgroups: comp.std.c Subject: Re: N2838: Types and sizes: "This changes the specification when the operand of sizeof is not an lvalue of VLA type"??? Date: Sun, 13 Nov 2022 06:42:18 -0800 Organization: A noiseless patient Spider Lines: 32 Message-ID: <86tu32ex11.fsf@linuxsc.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: reader01.eternal-september.org; posting-host="0d9d9adb12236acb6df358a6e34949d6"; logging-data="1560661"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18tvcMx40p06/CTWjfOvruV1iiDqJ8TmDU=" User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.4 (gnu/linux) Cancel-Lock: sha1:46ikRLBGry3eO69I8L06joIxxdQ= sha1:Lnv7FFwaySrTmizWDjIFNNPe+lU= Xref: csiph.com comp.std.c:6450 Andrey Tarasevich writes: > https://open-std.org/jtc1/sc22/wg14/www/docs/n2838.htm > > Section "3.2.1. Rationale" of that proposal begins with > > "This changes the specification when the operand of sizeof is > *not* an lvalue of VLA type [...]" > > Note the "not" in the above sentence: "not an lvalue of VLA type". > > And then it proceeds to demonstrate the proposed change with an > example in 3.2.2 where the `sizeof` in question (whose behavior will > supposedly change) is clearly applied to an lvalue of VLA type! > > So, what is that "not" doing in the initial sentence of 3.2.1? Is > this just a typo/miswording? Or am I missing something about the > intended meaning of that sentence? My reading of that statement in 3.2.1 is that it is wrong. The change proposed in 3.2 /does/ affect the semantics of sizeof with an operand that is an lvalue of VLA type, and also, AFAICT, does /not/ affect the semantics of sizeof with any other kind of operand. As to what may have caused it, I have nothing new to offer. The proposal document is poorly written. The changes proposed are either poorly written or poorly thought out, perhaps both. Sadly I believe the overall quality of the proposal is indicative of what is going on in the ISO C standard more generally.