On Fri, 13 Apr 2007 10:32:28 -0400, Barry Warsaw <[EMAIL PROTECTED]> wrote: >-----BEGIN PGP SIGNED MESSAGE----- >Hash: SHA1 > >I've been getting some test failures in Python 2.5 svn head on Mac OS >X 10.4.9 which I'm not getting on Linux (Ubuntu feisty beta). >test_sqlite and test_zipimport both fail, however, when run in >verbose mode (e.g. ./python.exe Lib/test/test_sqlite.py) both pass. > >But that's not exactly why I'm writing this email <wink>. In the >course of trying to debug this, I ran the following on my Mac: > >make TESTOPTS=-v test > >This runs the entire test suite in verbose mode, and you do get a lot >of output. However the test suite hangs on test_pty.py. In fact, if >you run that test alone: > >./python.exe Lib/test/test_pty.py > >it too hangs for me. The reason is that in verbose mode, debug() >actually prints stuff to stdout and on the Mac, when the child of the >pty.fork() writes to its stdout, it blocks and so the parent's waitpid >() never returns. This doesn't happen on Linux though; the child's >stdout prints don't block, it exits, and the parent continues after >the waitpid(). > >Here's a very simple program that reproduces the problem: > >- -----snip snip----- >import os, pty, sys > >pid, fd = pty.fork() >print >> sys.stderr, pid, fd >if pid: > os.waitpid(pid, 0) >else: > os._exit(0) >- -----snip snip----- > >stderr, stdout, doesn't matter. This hangs on the Mac but completes >successfully on Linux. Of course, in neither case do you see the >child's output. > >I don't know if this is caused by a bug in the Mac's pty >implementation or something we're doing wrong on that platform. I >played around with several modifications to pty.fork() on the Mac, >including letting it drop down to the openpty()/os.fork() code, even >adding an explicit ioctl(slave_fd, TIOCSCTTY) call which Stevens >chapter 19 recommends for 4.3+BSD. I can't get it to not block.
What about reading from the child in the parent before calling waitpid? > >Barring a fix to pty.fork() (or possibly os.forkpty()) for the Mac, >then I would like to at least make test_pty.py not block when run in >verbose mode. A very simple hack would add something like this to >the "if pid == pty.CHILD" stanza: "def debug(msg): pass", possibly >protected by a "if verbose:". A less icky hack would be to read the >output from the master_fd in the parent, though you have to be >careful with that on Linux else the read can throw an input/output >error. > >Disabling debug output is band-aid yes, and any application on the >Mac like the above snippet will still fail. If anybody has any >suggestions, I'm all ears, but I've reached the limit of my pty-fu. > I don't think this is an OS X PTY bug. Writing to a blocking file descriptor can block. Programs that do this need to account for the possibility. Jean-Paul _______________________________________________ Python-Dev mailing list [EMAIL PROTECTED] http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
