Path: csiph.com!eternal-september.org!feeder.eternal-september.org!nntp.eternal-september.org!.POSTED!not-for-mail From: Tim Rentsch Newsgroups: comp.lang.c Subject: Re: Expression statements (was Re: Meaning of "expression") Date: Wed, 19 Aug 2026 08:32:09 -0700 Organization: A noiseless patient Spider Lines: 52 Message-ID: <86ecfu15za.fsf@linuxsc.com> References: <10v7b32$2u85v$1@dont-email.me> <86ecipcbqa.fsf@linuxsc.com> <10vnlgu$382un$2@kst.eternal-september.org> <86bjdpayv0.fsf@linuxsc.com> <10vv49k$1aoa2$4@kst.eternal-september.org> <1107aq2$3grso$2@kst.eternal-september.org> <11093p9$1nauc$1@dont-email.me> <11095su$1obc$1@dont-email.me> <110981v$1nauc$2@dont-email.me> <1109ai6$1aa$1@dont-email.me> <110a4cv$b2kq$4@kst.eternal-september.org> <110etqg$1naub$9@dont-email.me> <110f1c5$1ltqf$1@dont-email.me> <110fdaf$1naub$11@dont-email.me> <110fkk2$1qf9f$2@kst.eternal-september.org> <111pr2q$5rbd$1@dont-email.me> <111q697$3cgp8$1@kst.eternal-september.org> <86qzlq7gkr.fsf@linuxsc.com> <111shoe$3vq40$3@kst.eternal-september.org> <86wlts5tbr.fsf@linuxsc.com> <115o0en$2rq0k$2@kst.eternal-september.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Date: Wed, 19 Aug 2026 15:32:10 +0000 (UTC) Injection-Info: dont-email.me; logging-data="2905177"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18wI9LHDZp+3mrO7H2JfFa54ye8O4oOMSA="; posting-host="d6f68e827472d35b9db1fc199aad88a7" User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.4 (gnu/linux) Cancel-Lock: sha1:NpBUXcyeoHtkV2uANTCcLvWZcY8= sha1:GHpNXOgnL/8RxvJsyPwayL3ycR8= sha256:14P2jtnVmtq2IdEltitLklmeSCO1JTH0eYV45Djar04= sha1:F6axFav08dbuvDQeVmVCSb9kGcU= sha256:HrhZp9qEMdCEjV1zlVlNHymIi4n94MZXwWPqBGABCqU= Xref: csiph.com comp.lang.c:401328 Keith Thompson writes: > Tim Rentsch writes: > >> Keith Thompson writes: >> >>> Tim Rentsch writes: >>> >>>> Keith Thompson writes: >>> >>> [...] >>> >>>>> For example, this program: >>>>> >>>>> #include >>>>> int main(void) { >>>>> const int result = printf("%ld\n", 0.3); >>>>> printf("printf returned %d\n", result); >>>>> } >>>>> >>>>> on my system prints: >>>>> >>>>> 140732048673560 >>>>> printf returned 16 >>>>> >>>>> gcc and clang warn about the format string. tcc doesn't. >>>>> >>>>> The (first) printf call was apparently successful because printf >>>>> has no way to know that the argument was of an incorrect type >>>>> (types don't really exist at run time). >>>> >>>> printf() could know if an argument were of an incorrect type, if >>>> an implementation chose to do so. >>> >>> Sure. I did write "on my system", where printf has no way to know >>> that the argument was of an incorrect type. >> >> The "on my system" applies to what the program prints. >> >> The paragraph that says "printf has no way to know" is a general >> statement, for any implementation of printf(). If you had meant it >> to apply only to your system, you should have said something like >> "because that printf had no way to know". Without any qualifying >> adjective or other indicator the statement is generic, not >> specific. > > [...] Certainly printf has no way defined by the language to know > whether its arguments are of the correct types. An implementation > could provide that information via some system-specific method, > [...] I'm glad to know we are in agreement.