|Summary:||closing stdout in a child python process means that process doesn't receive bytes from stdin anymore. I think.|
|Product:||cygwin||Reporter:||Zooko O'Whielacronx <zooko>|
|Component:||Cygwin Applications||Assignee:||Reini Urban <rurban>|
|Attachments:||the output from cygcheck -s -v -r|
Description Zooko O'Whielacronx 2008-11-10 23:15:05 UTC
When someone runs "bin/trial --reactor=select twisted.internet.test.test_process.ProcessTestsBuilder_PollReactor.test_ childConnectionLost" on cygwin, using the cygwin version of Python, either manually (which I've done on two cygwin installations), or from the twisted buildbot -- http://buildbot.twistedmatrix.com/builders/cygwin-py2.5-select -- then once the child process closes its fd #2, it subsequently receives no further bytes from its fd #1, even though the parent process has written some bytes to that pipe. I can reproduce this by running the Twisted unit tests, like this: step 1: get twisted: svn co svn://svn.twistedmatrix.com/svn/Twisted/trunk twisted step 2: cd into the top-level directory, and run trial: cd twisted && python ./bin/trial --reactor=select twisted.internet.test.test_process.ProcessTestsBuilder_PollReactor.test_ childConnectionLost On other platforms that cygwin (see the Twisted buildbot -- http://buildbot.twistedmatrix.com/supported?branch=trunk -- then this test exits quickly with success. On cygwin, using cygwin python.exe, this test instead enter an infinite loop as the child waits to receive further bytes on its stdin, and the parent waits for the child to respond to those bytes. (This doesn't happen on cygwin with the standard Win32 build of python.exe, of course, anymore than it happens on a Windows system without cygwin installed when using that executable.) I've opened a ticket about this on the twisted issue tracker as well: http://twistedmatrix.com/trac/ticket/3529 # closing stdout in a child process on cygwin means that process doesn't receive bytes from stdin anymore. I think. I've opened a ticket about this on the python issue tracker as well: http://bugs.python.org/issue4295 # closing stdout in a child process on cygwin means that process doesn't receive bytes from stdin anymore. I think. The version of the cygwin package of python is 2.5.1-2.
Comment 1 Zooko O'Whielacronx 2008-11-13 13:28:44 UTC
Created attachment 3060 [details] the output from cygcheck -s -v -r
Comment 2 Zooko O'Whielacronx 2008-11-13 16:10:29 UTC
Corinna Vinschen of cygwin requests a smaller test case: http://www.cygwin.com/ml/cygwin/2008-11/msg00166.html
Comment 3 Zooko O'Whielacronx 2009-01-14 04:40:52 UTC
Here is a smaller test case which shows incorrect behavior: http://twistedmatrix.com/trac/attachment/ticket/3529/demo.4.py I will also attempt to attach demo.4.py to this ticket. There are more test cases along with my notes about the behavior that they exhibited at: http://twistedmatrix.com/trac/ticket/3529
Comment 4 Zooko O'Whielacronx 2009-01-14 04:43:03 UTC
Oh, I'm sorry, demo.4.py shows correct behavior. The difference between demo.4.py -- which behaves correctly -- and "python ./bin/trial --reactor=select twisted.internet.test.test_process.ProcessTestsBuilder_PollReactor.test_ childConnectionLost" -- which behaves incorrectly -- is not understood.