From: Eric Blake <eblake@redhat.com>
To: cygwin@cygwin.com
Subject: Re: Cygwin's writev() non-standard behavior
Date: Wed, 23 Apr 2014 14:43:00 -0000 [thread overview]
Message-ID: <5357D176.4010203@redhat.com> (raw)
In-Reply-To: <20140423140635.156430@gmx.com>
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On 04/23/2014 08:06 AM, qq qq wrote:
> writev() does not accept count 0 but it should
POSIX says:
http://pubs.opengroup.org/onlinepubs/9699919799/functions/writev.html
If fildes refers to a regular file and all of the iov_len members in the
array pointed to by iov are 0, writev() shall return 0 and have no other
effect. For other file types, the behavior is unspecified.
>
> $ cat test.c
> #include <stdio.h>
> #include <errno.h>
> #include <stdlib.h>
> #include <string.h>
> #include <sys/uio.h>
>
> int main()
> {
> struct iovec vec;
>
> memset(&vec, 0, sizeof(vec));
> if (writev(1, &vec, 0) < 0)
But in your case, fd 1 is a terminal...
> Cygwin:
> $ gcc -Wall test.c
> $ ./a.exe
> writev: Invalid argument
so your argument is flawed - you have triggered undefined behavior.
That said, if you can reproduce it with ./a.exe > file, you have proven
a bug; furthermore, cygwin should emulate Linux behavior, even if POSIX
doesn't define the behavior.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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next prev parent reply other threads:[~2014-04-23 14:43 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-23 14:06 qq qq
2014-04-23 14:43 ` Eric Blake [this message]
2014-04-23 14:53 ` Eliot Moss
2014-04-23 15:29 ` Corinna Vinschen
2014-04-23 14:53 qq qq
2014-04-23 16:24 ` Eric Blake
2014-04-23 15:48 qq qq
2014-04-23 16:44 ` Corinna Vinschen
2014-04-23 18:44 ` Christopher Faylor
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