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Unable to exit pdb when script becomes invalid #75304

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jaraco opened this issue Aug 4, 2017 · 5 comments
Closed

Unable to exit pdb when script becomes invalid #75304

jaraco opened this issue Aug 4, 2017 · 5 comments
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stdlib Python modules in the Lib dir

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@jaraco
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jaraco commented Aug 4, 2017

BPO 31121
Nosy @jaraco, @xdegaye, @hexagonrecursion

Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2017-08-04.14:03:56.661>
labels = ['library']
title = 'Unable to exit pdb when script becomes invalid'
updated_at = <Date 2020-11-17.07:28:13.884>
user = 'https://github.com/jaraco'

bugs.python.org fields:

activity = <Date 2020-11-17.07:28:13.884>
actor = 'hexagonrecursion'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2017-08-04.14:03:56.661>
creator = 'jaraco'
dependencies = []
files = []
hgrepos = []
issue_num = 31121
keywords = []
message_count = 2.0
messages = ['299748', '381214']
nosy_count = 3.0
nosy_names = ['jaraco', 'xdegaye', 'hexagonrecursion']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue31121'
versions = ['Python 3.6']
@jaraco
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jaraco commented Aug 4, 2017

Similar to bpo-16180 and possible a duplicate of bpo-14743, if the script being run under pdb becomes invalid such as through a chdir operation, pdb will get trapped in a loop, catching its own exception.

$ mkdir foo
$ cat > foo/script.py
import os
os.chdir('foo')
$ python -m pdb foo/script.py
> /Users/jaraco/Dropbox/code/privacymate/harvester/foo/script.py(1)<module>()
-> import os
(Pdb) c
The program finished and will be restarted
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pdb.py", line 1667, in main
    pdb._runscript(mainpyfile)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pdb.py", line 1545, in _runscript
    with open(filename, "rb") as fp:
FileNotFoundError: [Errno 2] No such file or directory: 'foo/script.py'
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> /Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pdb.py(1545)_runscript()
-> with open(filename, "rb") as fp:
(Pdb) q
Post mortem debugger finished. The foo/script.py will be restarted
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pdb.py", line 1667, in main
    pdb._runscript(mainpyfile)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pdb.py", line 1545, in _runscript
    with open(filename, "rb") as fp:
FileNotFoundError: [Errno 2] No such file or directory: 'foo/script.py'
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> /Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pdb.py(1545)_runscript()
-> with open(filename, "rb") as fp:
(Pdb) q
Post mortem debugger finished. The foo/script.py will be restarted
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pdb.py", line 1667, in main
    pdb._runscript(mainpyfile)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pdb.py", line 1545, in _runscript
    with open(filename, "rb") as fp:
FileNotFoundError: [Errno 2] No such file or directory: 'foo/script.py'
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> /Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/pdb.py(1545)_runscript()
-> with open(filename, "rb") as fp:
(Pdb)

I suggest PDB should always pass exceptions when the stack trace terminates in the pdb module.

@jaraco jaraco added the stdlib Python modules in the Lib dir label Aug 4, 2017
@hexagonrecursion
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hexagonrecursion mannequin commented Nov 17, 2020

Another way to reproduce this that will continue to work once bpo-42383 is fixed is to delete or move the script while it's being debugged.

@ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
@erlend-aasland erlend-aasland mentioned this issue Jan 16, 2024
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@gaogaotiantian
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This does not reproduce in main anymore because the script path is remembered before it's being executed. chdir will not trap pdb anymore.

@jaraco
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jaraco commented Feb 6, 2024

I believe the issue is still reproducible. I reproduced in on Python 3.12.1, this time using the technique of deleting the file:

 draft @ mkdir foo
 draft @ cat > foo/script.py
import os
os.remove('foo/script.py')
raise ValueError()
 draft @ py -3.12 -m pdb foo/script.py
> /Users/jaraco/draft/foo/script.py(1)<module>()
-> import os
(Pdb) c
Traceback (most recent call last):
  File "/opt/homebrew/Cellar/python@3.12/3.12.1_1/Frameworks/Python.framework/Versions/3.12/lib/python3.12/pdb.py", line 1925, in main
    pdb._run(target)
  File "/opt/homebrew/Cellar/python@3.12/3.12.1_1/Frameworks/Python.framework/Versions/3.12/lib/python3.12/pdb.py", line 1719, in _run
    self.run(target.code)
  File "/opt/homebrew/Cellar/python@3.12/3.12.1_1/Frameworks/Python.framework/Versions/3.12/lib/python3.12/bdb.py", line 600, in run
    exec(cmd, globals, locals)
  File "<string>", line 1, in <module>
  File "/Users/jaraco/draft/foo/script.py", line 3, in <module>
ValueError
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> /Users/jaraco/draft/foo/script.py(3)<module>()
(Pdb) q
Post mortem debugger finished. The /Users/jaraco/draft/foo/script.py will be restarted
Traceback (most recent call last):
  File "/opt/homebrew/Cellar/python@3.12/3.12.1_1/Frameworks/Python.framework/Versions/3.12/lib/python3.12/pdb.py", line 1925, in main
    pdb._run(target)
  File "/opt/homebrew/Cellar/python@3.12/3.12.1_1/Frameworks/Python.framework/Versions/3.12/lib/python3.12/pdb.py", line 1719, in _run
    self.run(target.code)
             ^^^^^^^^^^^
  File "/opt/homebrew/Cellar/python@3.12/3.12.1_1/Frameworks/Python.framework/Versions/3.12/lib/python3.12/pdb.py", line 160, in code
    with io.open_code(self) as fp:
         ^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '/Users/jaraco/draft/foo/script.py'
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> /opt/homebrew/Cellar/python@3.12/3.12.1_1/Frameworks/Python.framework/Versions/3.12/lib/python3.12/pdb.py(160)code()
-> with io.open_code(self) as fp:
(Pdb) q
Post mortem debugger finished. The /Users/jaraco/draft/foo/script.py will be restarted
Traceback (most recent call last):
  File "/opt/homebrew/Cellar/python@3.12/3.12.1_1/Frameworks/Python.framework/Versions/3.12/lib/python3.12/pdb.py", line 1925, in main
    pdb._run(target)
  File "/opt/homebrew/Cellar/python@3.12/3.12.1_1/Frameworks/Python.framework/Versions/3.12/lib/python3.12/pdb.py", line 1719, in _run
    self.run(target.code)
             ^^^^^^^^^^^
  File "/opt/homebrew/Cellar/python@3.12/3.12.1_1/Frameworks/Python.framework/Versions/3.12/lib/python3.12/pdb.py", line 160, in code
    with io.open_code(self) as fp:
         ^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '/Users/jaraco/draft/foo/script.py'
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> /opt/homebrew/Cellar/python@3.12/3.12.1_1/Frameworks/Python.framework/Versions/3.12/lib/python3.12/pdb.py(160)code()
-> with io.open_code(self) as fp:

I've tested on main as well, at 7fdd423, and indeed the repro with deleting the file no longer falls into the loop:

 cpython main @ mkdir foo
 cpython main @ cat > foo/script.py
import os
os.remove('foo/script.py')
raise ValueError()
 cpython main @ ./python.exe -m pdb foo/script.py
> /Users/jaraco/code/python/cpython/foo/script.py(1)<module>()
-> import os
(Pdb) c
Traceback (most recent call last):
  File "/Users/jaraco/code/python/cpython/Lib/pdb.py", line 2294, in main
    pdb._run(target)
    ~~~~~~~~^^^^^^^^
  File "/Users/jaraco/code/python/cpython/Lib/pdb.py", line 2058, in _run
    self.run(target.code)
    ~~~~~~~~^^^^^^^^^^^^^
  File "/Users/jaraco/code/python/cpython/Lib/bdb.py", line 607, in run
    exec(cmd, globals, locals)
    ~~~~^^^^^^^^^^^^^^^^^^^^^^
  File "<string>", line 1, in <module>
  File "/Users/jaraco/code/python/cpython/foo/script.py", line 3, in <module>
ValueError
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> /Users/jaraco/code/python/cpython/foo/script.py(3)<module>()
(Pdb) q
Post mortem debugger finished. The /Users/jaraco/code/python/cpython/foo/script.py will be restarted

@gaogaotiantian
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Yeah it's fixed in main but not 3.12. It's also not a trivial fix so I'm not sure if we will backport the fix. The issue has been there for more than 6 years anyway.

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