Description

markshannon

opened on Apr 4, 2022

Issue body actions

BPO	47215
Nosy	@markshannon, @brandtbucher
PRs	bpo-47215: Add undocumented, unstable FrameStack API for use by greenlets and similar libraries. #32303

^{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 = 'https://github.com/markshannon'
closed_at = None
created_at = <Date 2022-04-04.11:59:07.553>
labels = ['expert-C-API', 'type-feature', '3.11']
title = 'Add "unstable" frame stack api'
updated_at = <Date 2022-04-04.12:09:47.075>
user = 'https://github.com/markshannon'

bugs.python.org fields:

activity = <Date 2022-04-04.12:09:47.075>
actor = 'Mark.Shannon'
assignee = 'Mark.Shannon'
closed = False
closed_date = None
closer = None
components = ['C API']
creation = <Date 2022-04-04.11:59:07.553>
creator = 'Mark.Shannon'
dependencies = []
files = []
hgrepos = []
issue_num = 47215
keywords = ['patch']
message_count = 1.0
messages = ['416665']
nosy_count = 2.0
nosy_names = ['Mark.Shannon', 'brandtbucher']
pr_nums = ['32303']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue47215'
versions = ['Python 3.11']

Linked PRs

• WIP: gh-91371: Add PyFrameStack C API #119596

Reacted by Hood Chatham

Activity

1. markshannon commented on Apr 4, 2022

   

   markshannon

   on Apr 4, 2022

   MemberAuthor

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   We need to provide an API to create, swap and free frame stacks for greenlets.

   Since this is primarily for greenlets (and any other stackful coroutines libraries that want to use it) it will be "unstable".

   In this case, by "unstable" I mean:

   1. Starts with an underscore
   2. Gets PyAPI_FUNC annotations, so we don't strip the symbols from the executable
   3. Undocumented, except for comments that say it is unstable.

   The API will be:

   typedef struct _frame_stack {
       _PyStackChunk *current_chunk;
       PyObject **top;
       PyObject **limit;
       int chunk_size;
   } _PyFrameStack;
   
   PyAPI_FUNC(void) _PyFrameStack_Init(_PyFrameStack *fs, int chunk_size);
   PyAPI_FUNC(void) _PyFrameStack_Swap(_PyFrameStack *fs);
   PyAPI_FUNC(void) _PyFrameStack_Free(_PyFrameStack *fs);
   
   
2. markshannon

   added

   3.11only security fixesonly security fixes

   on Apr 4, 2022
3. markshannon

   self-assigned this

   on Apr 4, 2022
4. markshannon

   added

   topic-C-API

   type-featureA feature request or enhancementA feature request or enhancement

   3.11only security fixesonly security fixes

   on Apr 4, 2022
5. markshannon

   self-assigned this

   on Apr 4, 2022
6. markshannon

   added

   topic-C-API

   type-featureA feature request or enhancementA feature request or enhancement

   on Apr 4, 2022
7. ezio-melotti

   transferred this issue fromon Apr 10, 2022
8. vstinner commented on May 27, 2024

   

   vstinner

   on May 27, 2024

   Member

   More actions

   greenlet code to save the Python thread state (C++): https://github.com/python-greenlet/greenlet/blob/937f150e07823ee03344aeeb5111c0bb371a831d/src/greenlet/TPythonState.cpp#L111

   greenlet is used by eventlet and gevent projects.

   PyOdide has similar code (in C): https://github.com/pyodide/pyodide/blob/d317e66d174efa203c59f094eb7714c0b90f7613/src/core/stack_switching/pystate.c#L161-L187
9. vstinner commented on May 27, 2024

   

   vstinner

   on May 27, 2024

   Member

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   cc @hoodmane

   Reacted by Donghee Na
10. vstinner

    added 3 commits that reference this issue on May 27, 2024

    WIP: pythongh-91371: Add PyFrameStack C API

    f495137

    WIP: pythongh-91371: Add PyFrameStack C API

    55eb346

    WIP: Draft PyFrameStack API

    8013b22
11. vstinner commented on May 28, 2024

    

    vstinner

    on May 28, 2024

    Member

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    Experimental greenlet change extracting the "save/restore" logic into a C API: python-greenlet/greenlet#407
12. vstinner commented on May 28, 2024

    

    vstinner

    on May 28, 2024

    Member

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    Members which should be saved/restored per Python version.

    Python 3.10 (4):

    • tstate->cframe
    • tstate->cframe->use_tracing
    • tstate->recursion_depth
    • tstate->trash_delete_nesting

    Python 3.11 (8):

    • tstate->cframe
    • tstate->cframe->current_frame
    • tstate->cframe->use_tracing
    • tstate->datastack_chunk
    • tstate->datastack_limit
    • tstate->datastack_top
    • tstate->recursion_remaining
    • tstate->trash_delete_nesting

    Python 3.12 (8):

    • tstate->c_recursion_remaining
    • tstate->cframe->current_frame
    • tstate->cframe
    • tstate->datastack_chunk
    • tstate->datastack_limit
    • tstate->datastack_top
    • tstate->py_recursion_remaining
    • tstate->trash.delete_nesting

    For Python 3.13, I'm not sure. I found 8 members:

    • tstate->c_recursion_remaining
    • tstate->context
    • tstate->current_frame (UPDATE)
    • tstate->datastack_chunk
    • tstate->datastack_limit
    • tstate->datastack_top
    • tstate->delete_later
    • tstate->py_recursion_remaining

    Reacted by Hood Chatham

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