Path: csiph.com!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Keith Thompson Newsgroups: comp.lang.c Subject: Re: Casting the return value of ... Date: Thu, 28 Mar 2024 12:38:21 -0700 Organization: None to speak of Lines: 25 Message-ID: <87frwatadu.fsf@nosuchdomain.example.com> References: <20240328105203.773@kylheku.com> MIME-Version: 1.0 Content-Type: text/plain Injection-Date: Thu, 28 Mar 2024 19:38:24 +0100 (CET) Injection-Info: dont-email.me; posting-host="2dfbf40368bf600f73fcb17ce635941b"; logging-data="3969551"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18v3AqoUPmWmxRxoJCwx7/0" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) Cancel-Lock: sha1:IjojRT6ERwOVN4/QUsbkayyqjpY= sha1:Ey/bxxuKFxwo/stPRzUpMfjCBlo= Xref: csiph.com comp.lang.c:384069 Kaz Kylheku <433-929-6894@kylheku.com> writes: [...] > Conversions between function pointers and data pointers are an > extension; it is not well-defined behavior in ISO C. > > Therefore we can neither say that ISO C doesn't require a cast there (it > imposes no requirements at all), nor that the conversion is fine with a > cast. > > The cast is /likely/ necessary, in order to correctly trigger the > extension. ISO C does require a cast. The cast is necessary to avoid a constraint violation and a mandatory diagnostic. The resulting behavior is undefined in ISO C, but defined by POSIX. Assigning a void* value to a pointer-to-function object without a cast violates the constraint for simple assignment (N1570 6.5.16.1p1). [...] -- Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com Working, but not speaking, for Medtronic void Void(void) { Void(); } /* The recursive call of the void */