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<4b59209a91e8384ec000e2724696791c AT smtp-cloud7 DOT xs4all DOT net> <935d8ce5-fd5c-3010-4664-bb2dc9b7ca2f AT cornell DOT edu> <20190729084552 DOT GL11632 AT calimero DOT vinschen DOT de> In-Reply-To: user-agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 authentication-results: spf=none (sender IP is ) smtp.mailfrom=kbrown AT cornell DOT edu; x-ms-exchange-purlcount: 1 x-ms-oob-tlc-oobclassifiers: OLM:9508; received-spf: None (protection.outlook.com: cornell.edu does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 Content-Type: text/plain; charset="utf-8" Content-ID: <12253C1713179B4BBBA028233FED9123 AT namprd04 DOT prod DOT outlook DOT com> MIME-Version: 1.0 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: ksb2 AT cornell DOT edu X-IsSubscribed: yes Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by delorie.com id x6TDaJvp001600 On 7/29/2019 9:18 AM, Ken Brown wrote: > On 7/29/2019 4:45 AM, Corinna Vinschen wrote: >> On Jul 27 15:24, Ken Brown wrote: >>> 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 just tried this myself and I can't reproduce the problem. 1000 runs, >> no error. > > Interesting. And you ran this under X11 in an xterm window? > >>> 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. >> >> Yeah, subprocess debugging is a problem in GDB. Given how this works, >> you can at least take grep out of the picture. Bash is doing all the >> lifting, so it's just bash and ls. Did you try to reproduce this under >> strace? > > Yes, but there I get an error (even under mintty) for a different reason: > > $ strace -o trace.out ls -lL <(grep bash .bashrc) > ls: cannot access '/dev/fd/63': No such file or directory > > The strace output shows a call to fhandler_process::exists on /proc/45036/fd/63; > here 45036 is the PID of 'ls'. And then I see an EBADF error. But I think > what's happening here might be that bash is parsing '<(grep bash .bashrc)' too > soon, so that '/dev/fd/63' isn't related to the 'ls' command. > > By the way, I've just tried a different experiment, in which I simplify the ls > command to 'ls <(grep bash .bashrc)'. When I run this under xterm, I get the > broken pipe error 98% of the time or more. But it's fine under mintty. I think I may have more-or-less figured out what's going on. The "broken pipe" error simply means that ls has exited before grep has finished writing. So grep is writing to a pipe that has no readers. If I replace 'ls' by 'cat', I don't get any errors. It remains a mystery to me why I was seeing the broken pipe only under X11, but I don't see any reason to think there's a problem. Ken -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple