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Date: Thu, 13 Aug 2009 16:15:20 -0400
From: Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Cygwin1.dll 1.7.0-5x: RSYNC failures in close() system call on  pipe  file descriptors
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On Thu, Aug 13, 2009 at 07:52:01PM +0000, Eric Blake wrote:
>cygwin <karl <at> sipxx.com> writes:
>
>> 
>> -               if (dup2(to_child_pipe[0], STDIN_FILENO) < 0 ||
>> -                   close(to_child_pipe[1]) < 0 ||
>> -                   close(from_child_pipe[0]) < 0 ||
>> -                   dup2(from_child_pipe[1], STDOUT_FILENO) < 0) {
>> -                       rsyserr(FERROR, errno, "Failed to dup/close");
>> +               if (dup2(to_child_pipe[0], STDIN_FILENO) < 0) {
>> +                       rsyserr(FERROR, errno, "Failed to dup2(to-0)");
>>                         exit_cleanup(RERR_IPC);
>>                 }
>> -               if (to_child_pipe[0] != STDIN_FILENO)
>> -                       close(to_child_pipe[0]);
>> -               if (from_child_pipe[1] != STDOUT_FILENO)
>> -                       close(from_child_pipe[1]);
>
>Ouch.  rsync has a bug even without your patch: if you run rsync with
>stdout closed (as opposed to redirected), then to_child_pipe[0] can be
>1, and you end up closing the just-duplicated from_child_pipe[1] that
>was copied to the new stdout.  To be correct, rsync must compare
>to_child_pipe[0] against both 0 and 1, not just 0 (likewise for
>from_child_pipe[1] against both 0 and 1, not just 1).  Amazing how
>often this type of bug reappears, too - historical cygwin has had it in
>the past with newlib's popen implementation (I fixed it 2006-08-22), as
>well as m4 1.4.13-1 having it due to code from gnulib (I fixed it
>2009-07- 17).

Just a point of order: Cygwin doesn't use the newlib version of
popen.

cgf

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