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Date: Sun, 12 Mar 2017 12:39:12 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: dd -- bs>=2G, error writing to /dev/null - possible bug? (win7; coreutils 8.26)
Message-ID: <20170312113912.GE3340@calimero.vinschen.de>
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On Mar 12 00:33, Josef Frank wrote:
>=20
> Dear all,
>=20
>=20
> dd utility has problems to write to /dev/null with bs>=3D2^31,
> while bs<2^31 is ok.
>=20
> Increasing bs further to 2^33 leads to extended error message
>=20
> For description see below

Thanks for the testcase.  It's a combination of two bugs:

- At a crucial point in write(2), Cygwin used an int variable where
  it should have used a ssize_t variable.  This fouled up the return
  value for lengths >=3D 2^31.

- When writing to the Windows NUL device, NtWriteFile only returns the
  lower 32 bits od the number of bytes written.  This fouls up the
  return value of write(2) for lengths >=3D 2^32.

I fixed the first problem and created a workaround for the second.

I uploaded new developer snapshots to https://cygwin.de/snapshots/
Please give 'em a try.


Thanks,
Corinna

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

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