Mailing-List: contact cygwin-help@sourceware.cygnus.com; run by ezmlm List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@sources.redhat.com Delivered-To: mailing list cygwin@sources.redhat.com From: Chris Faylor Date: Fri, 11 Aug 2000 22:47:36 -0400 To: cygwin@sources.redhat.com Subject: Re: fwrite inconsistency Message-ID: <20000811224736.B22901@cygnus.com> Reply-To: cygwin@sources.redhat.com Mail-Followup-To: cygwin@sources.redhat.com References: <200008120242.TAA12840@aleph.ssd.hal.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.6i In-Reply-To: <200008120242.TAA12840@aleph.ssd.hal.com>; from jjf@bcs.org.uk on Fri, Aug 11, 2000 at 07:42:58PM -0700 On Fri, Aug 11, 2000 at 07:42:58PM -0700, J. J. Farrell wrote: >> From: "Jimen.Ching" >> >> The problem below produces "0 0" as output on HPUX and Solaris 2.5 with gcc >> 2.8.x. But using gcc 2.95.x on cygwin, I get "0 1". I also tried using >> Borland BCC, and I also got "0 1". Is GCC trying to behave like MS >> compilers under cygwin? >> >> Is it correct for size2 to contain 1? What does ANSI/ISO say about this? >> >> ----------------------------------------------------- >> #include >> >> int >> main(int argc, char *argv[]) >> { >> int size1, size2; >> FILE *fp; >> >> fp = fopen("tst.log", "w"); >> size1 = fwrite(0, 1, 0, fp); >> size2 = fwrite(0, 0, 1, fp); >> printf("%d %d\n", size1, size2); >> >> return 0; >> } > >Standard C says that your program produces undefined behaviour >because of the first parameter you give to the fwrite() calls. >The rest of this discussion assumes that your program gives the >same results with a valid first parameter. > >Standard C doesn't comment on the effect of giving 0 for "size" >or "nmemb". It's clear from the definition that the first case >should always return 0. The value returned in the second case >depends on the implementor's view of whether or not a zero-length >write succeeds. > >XPG3 and the Standard Unix Specification explicitly say > > If size or nitems is 0, fwrite() returns 0 > >I haven't checked, but it's very likely that POSIX says the same. > >This looks like a bug in cygwin's fwrite(). Cygwin uses newlib's fwrite. If you send this bug report to newlib@sources.redhat.com you'll probably have better luck getting it fixed. cgf -- Want to unsubscribe from this list? Send a message to cygwin-unsubscribe@sourceware.cygnus.com