Re: 3.2.0-1: possible regression Cygwin DDL bug (W10) when using multiple pipes

[M2 <m2f2@libero.it>]

On 28/04/2021 16:36, Takashi Yano wrote:
> On Wed, 28 Apr 2021 15:38:13 +0200
> M2 via Cygwin <cygwin@cygwin.com> wrote:
>> Hi,
>> I found a possible regression issue between cygwin 3.1.7-1 and 3.2.0-1.
>>
>> The issue happens with "short" output in multiple piping, such as the following example:
>>
>>      dir | grep c | sed "s/^/foo/" | sed "s/oo/OO/"
>>
>> (the case I run is different, but the bug is exposed by something silly/simple as this)
>>
>>
>> In 3.1.7, all is fine and you get what you expect.
>>
>> In 3.2.0, 3 out of 4 executions hang: the last command on the pipeline (i.e. `sed "s/oo/OO/"`)
>> hangs forever, while all preceding commands (i.e. both `grep c` and `sed "s/^/foo/"`) terminate correctly.
>>
>> Attached, cygcheck outputs for both 3.1.7 and 3.2.0
> I cannot reproduce your problem.
>
> In 64 bit cygwin:
>
> ...
>
> In 32 bit cygwin:
> ...
>
Some clarification: I run a mixed configuration with Cygwin commands 
mostly ran in CMD.EXE shell.

In my installation it seems that output from a WINDOWS console program 
causes trouble when piped to a CYGWIN process.

Close repetition such as loops tend to cause the bug.


Consider the following cases. I have CYGWIN\BIN in my (CMD) PATH, and 
drive prefix set to "/"

Case 1: BASH shell - all CYGWIN commands - WORKS

  for i in {1..20} ; do ls -la | grep . | sed s/./foo/ | sed s/oo/OO/ ; done


Case 2: BASH shell - first command is a WINDOWS command - WORKS

  for i in {1..20} ; do /c/windows/system32/ipconfig.exe /all | grep . | 
sed s/./foo/ | sed s/oo/OO/ ; done


Case 3: CMD shell - all CYGWIN commands - WORKS

  for /l %i in (1,1,20) do ls -la | grep . | sed s/./foo/ | sed s/oo/OO/


Case 4: CMD shell - first command is a WINDOWS command - HANGS 50% of times

  for /l %i in (1,1,20) do ipconfig.exe /all | grep . | sed s/./foo/ | 
sed s/oo/OO/


Thanks!