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X-HELO: calimero.vinschen.de
Date: Fri, 28 Mar 2014 10:31:10 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: open(O_RDWR) and lseek() fail
Message-ID: <20140328093110.GA23367@calimero.vinschen.de>
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References: <op DOT xderrfffdyj81a AT monster DOT itedn32a DOT localdomain> <5334EF41 DOT 50809 AT redhat DOT com> <op DOT xde3qaa3dyj81a AT monster DOT itedn32a DOT localdomain>
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On Mar 28 13:48, Roy wrote:
> On Fri, 28 Mar 2014 11:40:49 +0800, Eric Blake <eblake AT redhat DOT com> wrote:
>=20
> >On 03/27/2014 07:29 PM, Roy wrote:
> >>Hello list,
> >>
> >>I wonder why lseek(SEEK_CUR) on open(O_RDWR) fails with errno=3D22, the
> >>code works on Linux:
> >>
> >>#include <stdio.h>
> >>#include <errno.h>
> >>#include <stdlib.h>
> >>#include <fcntl.h>
> >>int main(int argc, char** argv){
> >
> >Where's #include <unistd.h>?  It fails because you are missing the
> >prototype for lseeks, which means that the C compiler is trying to call
> >it with 'int offset' instead of 'off_t offset'.  Compile with -Wall.
> >
> >>
> >>Whats wrong with cygwin?
> >
> >Rather, fix the bugs in your code, and let the compiler help you.
> >
>=20
> Got it, but why enforcing the use of off_t here?
> I'm not going to use 64bit offsets.

It doesn't matter what you use, it matters what the function expects.
lseek expects off_t per POSIX:

http://pubs.opengroup.org/onlinepubs/9699919799/functions/lseek.html

and off_t is defined as 64 bit type.


Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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