[Python-bugs-list] [ python-Bugs-488730 ] os.popen() seg faults on FreeBSD 5
noreply@sourceforge.net
noreply@sourceforge.net
Tue, 11 Dec 2001 23:57:31 -0800
Bugs item #488730, was opened at 2001-12-03 21:14
You can respond by visiting:
http://sourceforge.net/tracker/?func=detail&atid=105470&aid=488730&group_id=5470
Category: Extension Modules
Group: Platform-specific
Status: Open
Resolution: None
Priority: 5
Submitted By: Marc Culler (marcculler)
Assigned to: Nobody/Anonymous (nobody)
Summary: os.popen() seg faults on FreeBSD 5
Initial Comment:
Here is the crash with Python 2.1.1 on my FreeBSD
5.0-current system:
[ace:culler]$ python
Python 2.1.1 (#5, Aug 18 2001, 17:41:43)
[GCC 2.95.3 20010315 (release)] on freebsd5
Type "copyright", "credits" or "license" for more
information.
>>> import os
>>> mypipe = os.popen('ls /')
Segmentation fault (core dumped)
No problem occurs when I do the same thing in
Python 2.0, which was compiled under FreeBSD 4,
but is running here under FreeBSD 5:
[ace:culler]$ python2.0
Python 2.0 (#2, Nov 16 2000, 22:22:48)
[GCC 2.95.2 19991024 (release)] on freebsd4
Type "copyright", "credits" or "license" for more
information.
>>> import os
>>> mypipe = os.popen('ls /')
>>> mypipe.readlines()
['COPYRIGHT\012', 'bin\012', 'boot\012', 'cdrom\012',
'compat\012', 'dev\012', 'dist\012', 'entropy\012',
'etc\012', 'home\012', 'kernel\012',
'kernel.GENERIC\012', 'kernel.old\012',
'kernel.prev\012', 'mnt\012', 'modules\012',
'modules.old\012', 'proc\012', 'root\012', 'sbin\012',
'shared\012', 'stand\012', 'sys\012', 'tmp\012',
'usr\012', 'var\012']
>>>
----------------------------------------------------------------------
>Comment By: Martin v. Löwis (loewis)
Date: 2001-12-11 23:57
Message:
Logged In: YES
user_id=21627
Could that be one of those "it's BSD, never mix threading
and non-threading C libraries" bugs? I find it surprising
that it crashes inside the C library; the only known causes
(besides genuine bugs) are:
- memory management got corrupted. Without seeing the source
of _fcntl, I think this is unlikely.
- caller and callee have different ideas of how structures
are layed out, due to being compiled with different
definitions of those structures.
Are you sure it is correct to link with both libc and libc_r
simultaneously? Are there additional variants of the C
library which only work in certain combinations? Is this
documented anywhere?
----------------------------------------------------------------------
Comment By: Marc Culler (marcculler)
Date: 2001-12-11 15:43
Message:
Logged In: YES
user_id=392704
As to the subtlety of this bug, I meant to point out that
Python 2.0, which presumably has a nearly identical posix
module, has a working os.popen(). On the other hand,
Python2.0 loads libc_r.so.4 rather than libc_r.so.5. So
maybe that is where the secret lies. Interestingly,
the size of that library has gone from 664784 to 108988.
That suggests that there were some rather major changes
there, doesn't it?
----------------------------------------------------------------------
Comment By: Marc Culler (marcculler)
Date: 2001-12-11 15:11
Message:
Logged In: YES
user_id=392704
Yes, I thought it looked like it was a FreeBSD bug too.
Unfortunately, though, my little test program produced
a nice listing of my / directory. I still think it is
FreeBSD's problem, but it is at least a little bit subtle.
I suppose I should build the latest FreeBSD sources before
proceeding any further with this.
#include <stdio.h>
int main(){
int c;
FILE *fp;
fp = popen("ls /", "r");
if (fp == NULL) {
fprintf(stderr, "popen returned NULL\n");
exit(-1);
}
while ((c = getc(fp)) != EOF) {
putchar(c);
}
printf("\nDone\n");
exit(0);
}
----------------------------------------------------------------------
Comment By: Guido van Rossum (gvanrossum)
Date: 2001-12-11 14:28
Message:
Logged In: YES
user_id=6380
Marc, the Python popen code (if you can see through the
#ifdefs for non-Unix platforms :-) is a pretty
straightforward call of the C library popen(). The crash you
receive suggests that it has nothing to do with Python. Can
you try a C program containing the same call? Something like
#include <stdio.h>
main()
{
popen("ls -l", "r");
}
Does this crash in the same way? If so, you may close this
bug report and report it to the FreeBSD folks instead...
----------------------------------------------------------------------
Comment By: Marc Culler (marcculler)
Date: 2001-12-11 14:14
Message:
Logged In: YES
user_id=392704
All I know so far is that, according to the stack trace, the
crash seems to occur in _fcntl in libc_r.so:
(gdb) run
Starting program: /usr/local/src/Python211/python
Python 2.1.1 (#14, Dec 11 2001, 15:55:41)
[GCC 2.95.3 20010315 (release)] on freebsd5
Type "copyright", "credits" or "license" for more
information.
>>> import os
>>> x = os.popen('ls /')
Program received signal SIGSEGV, Segmentation fault.
0x280e32ee in _fcntl () from /usr/lib/libc_r.so.5
(gdb) backtrace
#0 0x280e32ee in _fcntl () from /usr/lib/libc_r.so.5
#1 0x28391c99 in fdopen () from /usr/lib/libc.so.5
#2 0x2834bf30 in popen () from /usr/lib/libc.so.5
#3 0x80735b1 in posix_popen (self=0x0, args=0x80f488c)
at ./Modules/posixmodule.c:2936
#4 0x805921e in call_cfunction (func=0x80d0820,
arg=0x80f488c, kw=0x0)
at Python/ceval.c:2845
#5 0x8057cb1 in eval_code2 (co=0x8159ac0,
globals=0x80e0ccc, locals=0x80e0ccc,
args=0x0, argcount=0, kws=0x0, kwcount=0, defs=0x0,
defcount=0, closure=0x0)
at Python/ceval.c:1948
#6 0x8055171 in PyEval_EvalCode (co=0x8159ac0,
globals=0x80e0ccc,
locals=0x80e0ccc) at Python/ceval.c:341
#7 0x806ca8f in run_node (n=0x8158280, filename=0x80a202d
"<stdin>",
globals=0x80e0ccc, locals=0x80e0ccc, flags=0xbfbff70c)
at Python/pythonrun.c:1045
#8 0x806bc86 in PyRun_InteractiveOneFlags (fp=0x80c93a0,
filename=0x80a202d "<stdin>", flags=0xbfbff70c) at
Python/pythonrun.c:570
#9 0x806bae6 in PyRun_InteractiveLoopFlags (fp=0x80c93a0,
filename=0x80a202d "<stdin>", flags=0xbfbff70c) at
Python/pythonrun.c:510
#10 0x806b9db in PyRun_AnyFileExFlags (fp=0x80c93a0,
filename=0x80a202d "<stdin>", closeit=0,
flags=0xbfbff70c)
at Python/pythonrun.c:473
#11 0x805222c in Py_Main (argc=0, argv=0xbfbff784) at
Modules/main.c:320
#12 0x8051d04 in main (argc=1, argv=0xbfbff784) at
Modules/python.c:10
#13 0x8051c35 in _start ()
----------------------------------------------------------------------
Comment By: Martin v. Löwis (loewis)
Date: 2001-12-11 12:58
Message:
Logged In: YES
user_id=21627
Can't reproduce this on FreeBSD 4.4, either, using the
current CVS.
----------------------------------------------------------------------
Comment By: Guido van Rossum (gvanrossum)
Date: 2001-12-08 09:18
Message:
Logged In: YES
user_id=6380
I can't reproduce this, and I don't have access to a FreeBSD
5 machine. Can you debug this yourself? We'd welcome a
patch.
----------------------------------------------------------------------
You can respond by visiting:
http://sourceforge.net/tracker/?func=detail&atid=105470&aid=488730&group_id=5470