[ python-Bugs-1048808 ] test_subprocess 2.4b1 fails on FreeBSD 5.2
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Wed Oct 20 21:49:49 CEST 2004
Bugs item #1048808, was opened at 2004-10-17 21:24
Message generated for change (Comment added) made by astrand
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Category: Python Library
Group: Python 2.4
Status: Open
Resolution: None
Priority: 7
Submitted By: Shalabh Chaturvedi (shalabh)
Assigned to: Peter Åstrand (astrand)
Summary: test_subprocess 2.4b1 fails on FreeBSD 5.2
Initial Comment:
Platform: FreeBSD 5.2.1-RELEASE
Python version: 2.4b1
After untarring I just did 'make' and then 'make test'.
make test passes all except following (output of make
test):
----
test_subprocess
this bit of output is from a test of stdout in a
different process ...
test test_subprocess failed -- Traceback (most recent
call last):
File
"/usr/home/shalabh/down/Python-2.4b1/Lib/test/test_subprocess.py",
line 432, in test_close_fds
self.assertEqual(p.stdout.read(), "3")
AssertionError: '5' != '3'
----
Also, make test ends with:
----
*** Error code 1
Stop in /usr/home/shalabh/down/Python-2.4b1.
----
Don't know if above is expected when a test fails.
----------------------------------------------------------------------
>Comment By: Peter Åstrand (astrand)
Date: 2004-10-20 21:49
Message:
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user_id=344921
Strange. You could check if any other processes uses these
pipes with:
lsof | egrep "0xc541acc4|0xc541ad70"
----------------------------------------------------------------------
Comment By: Shalabh Chaturvedi (shalabh)
Date: 2004-10-20 20:38
Message:
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They are pipes:
Python 2.4b1 (#1, Oct 17 2004, 12:04:08)
[GCC 3.3.3 [FreeBSD] 20031106] on freebsd5
Type "help", "copyright", "credits" or "license" for more
information.
>>> import os, subprocess
>>> subprocess.call(["lsof", "-p", str(os.getpid())])
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE
NAME
<snipped seemingly irrelevant .so files and folders>
python 1609 shalabh 0u VCHR 5,1 0t15826 114
/dev/ttyp1
python 1609 shalabh 1u VCHR 5,1 0t15826 114
/dev/ttyp1
python 1609 shalabh 2u VCHR 5,1 0t15826 114
/dev/ttyp1
python 1609 shalabh 3u PIPE 0xc541acc4 16384
->0xc541ad70
python 1609 shalabh 4u PIPE 0xc541ad70 16384
->0xc541acc4
0
----------------------------------------------------------------------
Comment By: Peter Åstrand (astrand)
Date: 2004-10-20 20:26
Message:
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Do you have lsof on your system? In that case, you could try
this:
>>> import os, subprocess
>>> subprocess.call(["lsof", "-p", str(os.getpid())])
That should give you a hint of what fd 3 and 4 really are.
----------------------------------------------------------------------
Comment By: Shalabh Chaturvedi (shalabh)
Date: 2004-10-20 19:38
Message:
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Same:
$ python -S
Python 2.3.4 (#2, Oct 15 2004, 13:44:35)
[GCC 3.3.3 [FreeBSD] 20031106] on freebsd5
>>> import os
>>> os.dup(0)
5
The above behaviour is also seen with 2.4b1 using -S.
----------------------------------------------------------------------
Comment By: Fredrik Lundh (effbot)
Date: 2004-10-20 19:23
Message:
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Just curious, but what happens if you start Python using the -
S option:
$ python -S
>>> import os
>>> os.dup(0)
----------------------------------------------------------------------
Comment By: Peter Åstrand (astrand)
Date: 2004-10-20 15:06
Message:
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>>> import os
>>> os.dup(0)
5
I think this is the core of the problem. The test_close_fds
test works like this:
All file descriptors in the forked child (except 0,1,2) are
closed. Then the Python binary is executed via execvp(). A
small test program is passed to the Python binary via the -c
command line option. If the OS and subprocess module works
correctly, we can be sure of that by the time of the
execve() system call, only file descriptors (0,1,2) are open
(well, the errpipe as well, but let's leave that out for
now). But, by the time the Python binary starts executing
the small program, all sorts of things may have happened.
I'm not really sure we can trust Python not to open files
during startup. For example, if we have a PYTHONSTARTUP
file, that open file will have a file descriptor, perhaps 3.
On one hand, this bug could indicate a bug in the Python
interpreter itself: perhaps a file descriptor leak. On the
other hand, this test might be a bit too unsafe.
So probably, this test should be removed.
----------------------------------------------------------------------
Comment By: Shalabh Chaturvedi (shalabh)
Date: 2004-10-17 23:06
Message:
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Here's some more info. On my FreeBSD box, for both 2.3.4 and
2.4b1:
>>> import os
>>> os.dup(0)
5
But on my Win XP box for 2.3.3:
>>> import os
>>> os.dup(0)
3
I am guessing this may be relevant. Someone more
knowledgable can comment.
----------------------------------------------------------------------
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