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Add "unstable" frame stack api #91371

Open markshannon opened 2 years ago

markshannon commented 2 years ago
BPO 47215
Nosy @markshannon, @brandtbucher
PRs
  • python/cpython#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: ```python assignee = 'https://github.com/markshannon' closed_at = None created_at = labels = ['expert-C-API', 'type-feature', '3.11'] title = 'Add "unstable" frame stack api' updated_at = user = 'https://github.com/markshannon' ``` bugs.python.org fields: ```python activity = actor = 'Mark.Shannon' assignee = 'Mark.Shannon' closed = False closed_date = None closer = None components = ['C API'] creation = 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

    markshannon commented 2 years ago

    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);
    vstinner commented 4 months ago

    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

    vstinner commented 4 months ago

    cc @hoodmane

    vstinner commented 4 months ago

    Experimental greenlet change extracting the "save/restore" logic into a C API: https://github.com/python-greenlet/greenlet/pull/407

    vstinner commented 4 months ago

    Members which should be saved/restored per Python version.

    Python 3.10 (4):

    Python 3.11 (8):

    Python 3.12 (8):

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