Mailing List Archive: Python: Bugs

[Bug #126254] Traceback objects not properly garbage-collected

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noreply at sourceforge

Dec 18, 2000, 6:50 PM

Post #1 of 6 (230 views)
Permalink

[Bug #126254] Traceback objects not properly garbage-collected

Bug #126254, was updated on 2000-Dec-18 17:50
Here is a current snapshot of the bug.

Project: Python
Category: Python Interpreter Core
Status: Open
Resolution: None
Bug Group: None
Priority: 5
Submitted by: nobody
Assigned to : nobody
Summary: Traceback objects not properly garbage-collected

Details: System info:
============

Python 2.0 (#1, Dec 18 2000, 16:47:02)
[GCC 2.95.2 20000220 (Debian GNU/Linux)] on linux2

Linux phil 2.2.18 #1 Mon Dec 18 14:49:56 PST 2000 i686 unknown

Sample code:
============

import sys

class fooclass:
def __init__(self):
print 'CONSTRUCTED'

def withtb(self, doit=0):
try:
raise "foo"
except:
if doit:
tb = sys.exc_info()[2]

def __del__(self):
print 'DESTROYED'

if __name__ == '__main__':
foo = fooclass()
if len(sys.argv) > 1:
foo.withtb(1)
else:
foo.withtb(0)
del foo

How to reproduce:
=================

Run the above python script:

1. Without any argument: the withtb() method exception handler does
not retrieve any traceback object. The program prints
`CONSTRUCTED' and `DESTROYED'.

2. With some arguments: the withtb() method exception handler
retrieves a traceback object and stores it in the `tb' local
variable. However `DESTROYED' never gets printed out. I think
that the `foo' object will never be garbage collected anymore.

Workaround:
===========

Deleting the `tb' object seems to restore things:

if doit:
tb = sys.exc_info()[2]
del tb

Other:
======

I've found this problem also in python 1.5.2 and python 1.6.

Possible cause:
===============

I would tend to think that we're creating a circular loop which
cannot be garbage collected:

- `tb' holds a reference to the traceback object
- the traceback object holds a reference to the local scope
- the local scope holds a reference to the `tb' variable

The only way out is to break the circular reference by hand,
although it's annoying.

Phil - phil [at] commerceflow

For detailed info, follow this link:
http://sourceforge.net/bugs/?func=detailbug&bug_id=126254&group_id=5470

noreply at sourceforge

Dec 18, 2000, 9:21 PM

Post #2 of 6 (230 views)
Permalink

[Bug #126254] Traceback objects not properly garbage-collected [In reply to]

noreply at sourceforge

Dec 20, 2000, 7:49 PM

Post #3 of 6 (230 views)
Permalink

[Bug #126254] Traceback objects not properly garbage-collected [In reply to]

Bug #126254, was updated on 2000-Dec-18 17:50
Here is a current snapshot of the bug.

Project: Python
Category: Python Interpreter Core
Status: Closed
Resolution: Invalid
Bug Group: Not a Bug
Priority: 5
Submitted by: nobody
Assigned to : gvanrossum
Summary: Traceback objects not properly garbage-collected

Details: System info:
============

Python 2.0 (#1, Dec 18 2000, 16:47:02)
[GCC 2.95.2 20000220 (Debian GNU/Linux)] on linux2

Linux phil 2.2.18 #1 Mon Dec 18 14:49:56 PST 2000 i686 unknown

Sample code:
============

import sys

class fooclass:
def __init__(self):
print 'CONSTRUCTED'

def withtb(self, doit=0):
try:
raise "foo"
except:
if doit:
tb = sys.exc_info()[2]

def __del__(self):
print 'DESTROYED'

if __name__ == '__main__':
foo = fooclass()
if len(sys.argv) > 1:
foo.withtb(1)
else:
foo.withtb(0)
del foo

How to reproduce:
=================

Run the above python script:

1. Without any argument: the withtb() method exception handler does
not retrieve any traceback object. The program prints
`CONSTRUCTED' and `DESTROYED'.

2. With some arguments: the withtb() method exception handler
retrieves a traceback object and stores it in the `tb' local
variable. However `DESTROYED' never gets printed out. I think
that the `foo' object will never be garbage collected anymore.

Workaround:
===========

Deleting the `tb' object seems to restore things:

if doit:
tb = sys.exc_info()[2]
del tb

Other:
======

I've found this problem also in python 1.5.2 and python 1.6.

Possible cause:
===============

I would tend to think that we're creating a circular loop which
cannot be garbage collected:

- `tb' holds a reference to the traceback object
- the traceback object holds a reference to the local scope
- the local scope holds a reference to the `tb' variable

The only way out is to break the circular reference by hand,
although it's annoying.

Phil - phil [at] commerceflow

Follow-Ups:

Date: 2000-Dec-20 18:49
By: nobody

Comment:
Could I know why this was deemed to be `Invalid' ?

Phil - phil [at] commerceflow

-------------------------------------------------------

Date: 2000-Dec-18 20:21
By: gvanrossum

Comment:
This is not a bug. Saving the traceback as a local variable creates a circular reference that prevents garbage collection.

If you don't understand this answer, please write help [at] python

-------------------------------------------------------

For detailed info, follow this link:
http://sourceforge.net/bugs/?func=detailbug&bug_id=126254&group_id=5470

noreply at sourceforge

Dec 20, 2000, 7:50 PM

Post #4 of 6 (230 views)
Permalink

[Bug #126254] Traceback objects not properly garbage-collected [In reply to]

Bug #126254, was updated on 2000-Dec-18 17:50
Here is a current snapshot of the bug.

Project: Python
Category: Python Interpreter Core
Status: Closed
Resolution: Invalid
Bug Group: Not a Bug
Priority: 5
Submitted by: nobody
Assigned to : gvanrossum
Summary: Traceback objects not properly garbage-collected

Details: System info:
============

Python 2.0 (#1, Dec 18 2000, 16:47:02)
[GCC 2.95.2 20000220 (Debian GNU/Linux)] on linux2

Linux phil 2.2.18 #1 Mon Dec 18 14:49:56 PST 2000 i686 unknown

Sample code:
============

import sys

class fooclass:
def __init__(self):
print 'CONSTRUCTED'

def withtb(self, doit=0):
try:
raise "foo"
except:
if doit:
tb = sys.exc_info()[2]

def __del__(self):
print 'DESTROYED'

if __name__ == '__main__':
foo = fooclass()
if len(sys.argv) > 1:
foo.withtb(1)
else:
foo.withtb(0)
del foo

How to reproduce:
=================

Run the above python script:

1. Without any argument: the withtb() method exception handler does
not retrieve any traceback object. The program prints
`CONSTRUCTED' and `DESTROYED'.

2. With some arguments: the withtb() method exception handler
retrieves a traceback object and stores it in the `tb' local
variable. However `DESTROYED' never gets printed out. I think
that the `foo' object will never be garbage collected anymore.

Workaround:
===========

Deleting the `tb' object seems to restore things:

if doit:
tb = sys.exc_info()[2]
del tb

Other:
======

I've found this problem also in python 1.5.2 and python 1.6.

Possible cause:
===============

I would tend to think that we're creating a circular loop which
cannot be garbage collected:

- `tb' holds a reference to the traceback object
- the traceback object holds a reference to the local scope
- the local scope holds a reference to the `tb' variable

The only way out is to break the circular reference by hand,
although it's annoying.

Phil - phil [at] commerceflow

Follow-Ups:

Date: 2000-Dec-20 18:50
By: nobody

Comment:
oops, didn't see you comment.
Forget about my question...

Phil - phil [at] commerceflow
-------------------------------------------------------

Date: 2000-Dec-20 18:49
By: nobody

Comment:
Could I know why this was deemed to be `Invalid' ?

Phil - phil [at] commerceflow

-------------------------------------------------------

Date: 2000-Dec-18 20:21
By: gvanrossum

Comment:
This is not a bug. Saving the traceback as a local variable creates a circular reference that prevents garbage collection.

If you don't understand this answer, please write help [at] python

-------------------------------------------------------

For detailed info, follow this link:
http://sourceforge.net/bugs/?func=detailbug&bug_id=126254&group_id=5470

noreply at sourceforge

Dec 20, 2000, 7:59 PM

Post #5 of 6 (230 views)
Permalink

[Bug #126254] Traceback objects not properly garbage-collected [In reply to]

Bug #126254, was updated on 2000-Dec-18 17:50
Here is a current snapshot of the bug.

Project: Python
Category: Python Interpreter Core
Status: Closed
Resolution: Invalid
Bug Group: Not a Bug
Priority: 5
Submitted by: nobody
Assigned to : gvanrossum
Summary: Traceback objects not properly garbage-collected

Details: System info:
============

Python 2.0 (#1, Dec 18 2000, 16:47:02)
[GCC 2.95.2 20000220 (Debian GNU/Linux)] on linux2

Linux phil 2.2.18 #1 Mon Dec 18 14:49:56 PST 2000 i686 unknown

Sample code:
============

import sys

class fooclass:
def __init__(self):
print 'CONSTRUCTED'

def withtb(self, doit=0):
try:
raise "foo"
except:
if doit:
tb = sys.exc_info()[2]

def __del__(self):
print 'DESTROYED'

if __name__ == '__main__':
foo = fooclass()
if len(sys.argv) > 1:
foo.withtb(1)
else:
foo.withtb(0)
del foo

How to reproduce:
=================

Run the above python script:

1. Without any argument: the withtb() method exception handler does
not retrieve any traceback object. The program prints
`CONSTRUCTED' and `DESTROYED'.

2. With some arguments: the withtb() method exception handler
retrieves a traceback object and stores it in the `tb' local
variable. However `DESTROYED' never gets printed out. I think
that the `foo' object will never be garbage collected anymore.

Workaround:
===========

Deleting the `tb' object seems to restore things:

if doit:
tb = sys.exc_info()[2]
del tb

Other:
======

I've found this problem also in python 1.5.2 and python 1.6.

Possible cause:
===============

I would tend to think that we're creating a circular loop which
cannot be garbage collected:

- `tb' holds a reference to the traceback object
- the traceback object holds a reference to the local scope
- the local scope holds a reference to the `tb' variable

The only way out is to break the circular reference by hand,
although it's annoying.

Phil - phil [at] commerceflow

Follow-Ups:

Date: 2000-Dec-20 18:59
By: tim_one

Comment:
"Invalid" is a just a word -- it comes with SF bug system and isn't defined anywhere. By convention, we pair Not-A-Bug with Invalid, for lack of something better to do. Not-A-Bug means it's not a bug <wink>: you may not like the answer, but Guido is saying it's functioning as designed and he has no plans to change that.
-------------------------------------------------------

Date: 2000-Dec-20 18:50
By: nobody

Comment:
oops, didn't see you comment.
Forget about my question...

Phil - phil [at] commerceflow
-------------------------------------------------------

Date: 2000-Dec-20 18:49
By: nobody

Comment:
Could I know why this was deemed to be `Invalid' ?

Phil - phil [at] commerceflow

-------------------------------------------------------

Date: 2000-Dec-18 20:21
By: gvanrossum

Comment:
This is not a bug. Saving the traceback as a local variable creates a circular reference that prevents garbage collection.

If you don't understand this answer, please write help [at] python

-------------------------------------------------------

For detailed info, follow this link:
http://sourceforge.net/bugs/?func=detailbug&bug_id=126254&group_id=5470

noreply at sourceforge

Dec 27, 2000, 3:21 PM

Post #6 of 6 (230 views)
Permalink

[Bug #126254] Traceback objects not properly garbage-collected [In reply to]

Bug #126254, was updated on 2000-Dec-18 17:50
Here is a current snapshot of the bug.

Project: Python
Category: Python Interpreter Core
Status: Closed
Resolution: Invalid
Bug Group: Not a Bug
Priority: 5
Submitted by: nobody
Assigned to : gvanrossum
Summary: Traceback objects not properly garbage-collected

Details: System info:
============

Python 2.0 (#1, Dec 18 2000, 16:47:02)
[GCC 2.95.2 20000220 (Debian GNU/Linux)] on linux2

Linux phil 2.2.18 #1 Mon Dec 18 14:49:56 PST 2000 i686 unknown

Sample code:
============

import sys

class fooclass:
def __init__(self):
print 'CONSTRUCTED'

def withtb(self, doit=0):
try:
raise "foo"
except:
if doit:
tb = sys.exc_info()[2]

def __del__(self):
print 'DESTROYED'

if __name__ == '__main__':
foo = fooclass()
if len(sys.argv) > 1:
foo.withtb(1)
else:
foo.withtb(0)
del foo

How to reproduce:
=================

Run the above python script:

1. Without any argument: the withtb() method exception handler does
not retrieve any traceback object. The program prints
`CONSTRUCTED' and `DESTROYED'.

2. With some arguments: the withtb() method exception handler
retrieves a traceback object and stores it in the `tb' local
variable. However `DESTROYED' never gets printed out. I think
that the `foo' object will never be garbage collected anymore.

Workaround:
===========

Deleting the `tb' object seems to restore things:

if doit:
tb = sys.exc_info()[2]
del tb

Other:
======

I've found this problem also in python 1.5.2 and python 1.6.

Possible cause:
===============

I would tend to think that we're creating a circular loop which
cannot be garbage collected:

- `tb' holds a reference to the traceback object
- the traceback object holds a reference to the local scope
- the local scope holds a reference to the `tb' variable

The only way out is to break the circular reference by hand,
although it's annoying.

Phil - phil [at] commerceflow

Follow-Ups:

Date: 2000-Dec-27 14:21
By: gvanrossum

Comment:
Note that the bug report was about 1.5.2 and 1.6. This should be fixed by
the cycle collection in 2.0, shouldn't it?

-------------------------------------------------------

Date: 2000-Dec-20 18:59
By: tim_one

Comment:
"Invalid" is a just a word -- it comes with SF bug system and isn't defined
anywhere. By convention, we pair Not-A-Bug with Invalid, for lack of
something better to do. Not-A-Bug means it's not a bug <wink>: you may
not like the answer, but Guido is saying it's functioning as designed and
he has no plans to change that.
-------------------------------------------------------

Date: 2000-Dec-20 18:50
By: nobody

Comment:
oops, didn't see you comment.
Forget about my question...

Phil - phil [at] commerceflow
-------------------------------------------------------

Date: 2000-Dec-20 18:49
By: nobody

Comment:
Could I know why this was deemed to be `Invalid' ?

Phil - phil [at] commerceflow

-------------------------------------------------------

Date: 2000-Dec-18 20:21
By: gvanrossum

Comment:
This is not a bug. Saving the traceback as a local variable creates a
circular reference that prevents garbage collection.

If you don't understand this answer, please write help [at] python

-------------------------------------------------------

For detailed info, follow this link:
http://sourceforge.net/bugs/?func=detailbug&bug_id=126254&group_id=5470

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