Description

gaogaotiantian

opened on Mar 21, 2023

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This issue is related to #101673 , where f_locals being accessed during the debugging clears the changes of local variables. We need to only do one access of f_locals before giving back control.

def f():
    a = 1
    breakpoint()
    print(a)

f()

> /home/gaogaotiantian/programs/mycpython/example.py(4)f()
-> print(a)
(Pdb) p a
1
(Pdb) !a = 2
(Pdb) p a
2
(Pdb) u
> /home/gaogaotiantian/programs/mycpython/example.py(6)<module>()
-> f()
(Pdb) d
> /home/gaogaotiantian/programs/mycpython/example.py(4)f()
-> print(a)
(Pdb) p a
1

The worst part is, print_stack_entry calls format_stack_entry which is a bdb function, and it accesses f_locals. To keep the maximum compatibility of bdb, I decided to leave it alone and only fix pdb.

Linked PRs

• gh-102864: Remove access to f_locals in pdb #102865
• gh-102864: Add switching frame test for pdb #119564

Activity

1. gaogaotiantian

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Mar 21, 2023
2. gaogaotiantian commented on Mar 21, 2023

   

   gaogaotiantian

   on Mar 21, 2023

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   @iritkatriel could you take a look at the issue when you have some time as you reviewed the related one so you might already know the fundamental problem.
3. gaogaotiantian

   changed the title [-]Switching frame will erase the local variable changes[/-] [+]Switching frame will erase the local variable changes in pdb[/+] on Mar 21, 2023
4. iritkatriel commented on Mar 21, 2023

   

   iritkatriel

   on Mar 21, 2023

   Member

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   When was this issue introduced? Is it part of the 3.10/3.11 changes to frames?
5. gaogaotiantian commented on Mar 21, 2023

   

   gaogaotiantian

   on Mar 21, 2023

   MemberAuthor

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   Unfortunately no. This issue has been there for a long time. As far as I can tell, you can repro it on 3.8. If I had to guess, it's probably when Python started using FAST instead of local variable dict.
6. arhadthedev

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   on Mar 22, 2023
7. gaogaotiantian commented on May 5, 2024

   

   gaogaotiantian

   on May 5, 2024

   MemberAuthor

   More actions

   This is fixed by PEP 667.

   Reacted by John Jones
8. gaogaotiantian

   closed this as completedon May 5, 2024
9. iritkatriel

   added a commit that references this issue on May 26, 2024

   gh-102864: Add switching frame test for pdb (#119564)

   5d04cc5
10. estyxx

    added a commit that references this issue on Jul 17, 2024

    pythongh-102864: Add switching frame test for pdb (python#119564)

    a85ce6a

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