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Date:	Mon, 18 Dec 2017 16:27:25 -0800 (PST)
From:	Steven Penny <svnpenn AT gmail DOT com>
X-Google-Original-From:	Steven Penny
To:	cygwin AT cygwin DOT com
Subject:	Re: Wrong file position after writing 65537 bytes to block device
References:	<20171218131035 DOT GB11285 AT calimero DOT vinschen DOT de>
User-Agent:	Tryst/2.0.1 (github.com/svnpenn/tryst)

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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