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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