Date: Thu, 7 Aug 2008 12:19:20 -0500 (CDT) From: "Sean C. Farley" <scf@FreeBSD.org> To: Jeremy Chadwick <koitsu@FreeBSD.org> Cc: hackers@FreeBSD.org Subject: Re: strange issue reading /dev/null Message-ID: <alpine.BSF.1.10.0808071216150.2133@thor.farley.org> In-Reply-To: <20080807170235.GA39461@eos.sc1.parodius.com> 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> <20080807170235.GA39461@eos.sc1.parodius.com>
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On Thu, 7 Aug 2008, Jeremy Chadwick wrote:
> 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:
You are correct; I did not use -O.
> $ 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
Heh.
> $ 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. :-)
Grr! Optimization should not be a requirement for checking for
uninitialized variables. Yes, gcc adds "fun" to development.
Sean
--
scf@FreeBSD.org
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