From: Steven Penny <svnpenn@gmail.com>
To: cygwin@cygwin.com
Subject: Re: Wrong file position after writing 65537 bytes to block device
Date: Tue, 19 Dec 2017 05:03:00 -0000 [thread overview]
Message-ID: <5a385ced.195b9d0a.d434.5400@mx.google.com> (raw)
In-Reply-To: <20171218131035.GB11285@calimero.vinschen.de>
On Mon, 18 Dec 2017 14:10:35, Corinna Vinschen wrote:
> In general, the writes on disk devices is sector-oriented. Howewver,
> in this case ftell should have returned 65536. The problem here is
> that the newlib implmentation of ftell/ftello performs an fflush
> when called on a write stream since about 2008 to adjust for appending
> streams. Given your example (thanks for the testcase!) this seems
> pretty wrong. Looking further it turns out that neither glibc nor BSD
> actually calls fflush in this case. There's only a special case for
> appending streams, but this calls lseek, not fflush.
>
> Looks like a patch is required. Stay tuned.
is it though? he says "write 65536 + 1 bytes", but as far as i can tell, you
cant do that. quoting myself:
> Seeking, reading and writing must all be done in multiples of sector size, in
> my case 512 bytes
http://web.archive.org/web/stackoverflow.com/questions/37228874/how-to-fwrite-to-removable-volume
so it would make sense that the position becomes "65536 + 512"
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next prev parent reply other threads:[~2017-12-19 0:27 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-16 6:13 Ivan Kozik
2017-12-18 16:32 ` Corinna Vinschen
2017-12-19 5:03 ` Steven Penny [this message]
2017-12-19 10:20 ` Corinna Vinschen
2017-12-19 16:36 ` Ivan Kozik
2017-12-19 17:43 ` Eric Blake
2017-12-19 18:18 ` Ivan Kozik
2017-12-19 18:36 ` Corinna Vinschen
2017-12-20 5:47 ` Ivan Kozik
2017-12-20 23:59 ` Kaz Kylheku
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