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From: Ken Brown <kbrown@cornell.edu>
To: "cygwin@cygwin.com" <cygwin@cygwin.com>
Subject: Re: Regression (last snapshot)
Date: Sat, 27 Jul 2019 15:24:49 +0000
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On 7/27/2019 6:21 AM, Houder wrote:
> On Fri, 26 Jul 2019 22:12:43, Ken Brown  wrote:
> 
>> On 7/22/2019 2:47 PM, Houder wrote:
> 
>>> The specific regression as reported, has gone.
>>>
>>> 64-@@ uname -a
>>> CYGWIN_NT-6.1 Seven 3.1.0s(0.339/5/3) 2019-07-22 16:43 x86_64 Cygwin
>>> 64-@@ ls -lL <(grep bash .bashrc)
>>> pr-------- 1 Henri None 0 Jul 22 20:36 /dev/fd/63
>>
> Over all the behavior has simularity w/ the error reported by David Karr:
> 
>      https://cygwin.com/ml/cygwin/2019-07/msg00150.html
>      ( Piping input from subprocess loses track of temp file )

Thanks, I hadn't noticed that.

The situation is more complicated than what I reported.  First, it happens even 
in cygwin-3.0.7, as David Karr's report suggests.  Second, it's true that I can 
only reproduce it under X11, but the pattern is not as regular as I thought.  I 
just ran the ls command 1000 times in an xterm window under cygwin-3.0.7, and I 
got the "Broken pipe" error 390 times, with a varying number of consecutive 
successful runs between the errors.

Repeating this under the 20190722 or 20190725 snapshots gave slightly worse 
results (close to 500 errors).  Using my own unoptimized build of cygwin1.dll, 
the error count went up to about 650.

I tried running under gdb, but I couldn't get grep to fail.  More precisely, I 
didn't see an error message from grep.  Every run looked like this:

$ gdb bash
GNU gdb (GDB) (Cygwin 8.2.1-1) 8.2.1
[...]
(gdb) r -c 'ls -lL <(grep bash .bashrc)'
Starting program: /usr/bin/bash -c 'ls -lL <(grep bash .bashrc)'
[...]
pr-------- 1 kbrown None 0 2019-07-27 11:07 /dev/fd/63
[...]
[Inferior 1 (process 21712) exited normally]

It would be better to be able to debug ls and/or grep, but I don't know how to 
get to subprocesses in gdb.  And I think I have to start with 'gdb bash' in 
order for the process substitution to happen.

Ken

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