Date: Thu, 7 Aug 2008 10:02:35 -0700 From: Jeremy Chadwick <koitsu@FreeBSD.org> To: "Sean C. Farley" <scf@FreeBSD.org> Cc: Gabor Kovesdan <gabor@kovesdan.org>, fjoe@FreeBSD.org, hackers@FreeBSD.org Subject: Re: strange issue reading /dev/null Message-ID: <20080807170235.GA39461@eos.sc1.parodius.com> In-Reply-To: <alpine.BSF.1.10.0808071150460.2133@thor.farley.org> References: <489B0ACD.80008@kovesdan.org> <alpine.BSF.1.10.0808071058020.1056@thor.farley.org> <489B22BD.5050109@kovesdan.org> <alpine.BSF.1.10.0808071150460.2133@thor.farley.org>
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On Thu, Aug 07, 2008 at 11:54:10AM -0500, Sean C. Farley wrote: > On Thu, 7 Aug 2008, Gabor Kovesdan wrote: > >> Sean C. Farley ha scritto: >>> You are testing c which has not been set. It works OK if you set c >>> then do the test: >>> >>> + c = fgetc(f); >>> if (c != EOF) >>> - printf("%c\n", fgetc(f)); >>> + printf("%c\n", c); >> Yes, you are right, this is what I meant, I'm just a bit >> disorganised.... >> Thanks! > > You are welcome. > > Actually, what I found odd was that the base gcc did not warn about > using an uninitialized variable using -Wall. Probably because you didn't use -O. -Wall includes -Wuninitialized, but -Wuninitialized only applies if you use optimisation. gcc won't bail if you use -Wall without -O, for obvious reasons. Case in point: $ gcc -Wall -o x x.c x.c: In function 'main': x.c:14: warning: control reaches end of non-void function $ gcc -Wuninitialized -o x x.c cc1: warning: -Wuninitialized is not supported without -O $ gcc -Wall -O -o x x.c x.c: In function 'main': x.c:14: warning: control reaches end of non-void function x.c:12: warning: 'c' is used uninitialized in this function gcc -- finding new ways every day to drive programmers crazy. :-) -- | Jeremy Chadwick jdc at parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB |
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