python / python/cpython

Bitfield Union does not work for bit widths greater than 8 bits

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extension-modules topic-ctypes type-bug
Dominant language
Python
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Description

BPO 39407
Nosy @vsajip, @amauryfa, @abalkin, @meadori
Files
  • python_struct_union_bug.py
  • 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 2020-01-21.09:20:46.369>
    labels = ['ctypes', 'type-bug', '3.7']
    title = 'Bitfield Union does not work for bit widths greater than 8 bits'
    updated_at = <Date 2020-01-23.07:49:15.925>
    user = 'https://bugs.python.org/jschulte'
    

    bugs.python.org fields:

    activity = <Date 2020-01-23.07:49:15.925>
    actor = 'ammar2'
    assignee = 'none'
    closed = False
    closed_date = None
    closer = None
    components = ['ctypes']
    creation = <Date 2020-01-21.09:20:46.369>
    creator = 'jschulte'
    dependencies = []
    files = ['48856']
    hgrepos = []
    issue_num = 39407
    keywords = []
    message_count = 1.0
    messages = ['360372']
    nosy_count = 5.0
    nosy_names = ['vinay.sajip', 'amaury.forgeotdarc', 'belopolsky', 'meador.inge', 'jschulte']
    pr_nums = []
    priority = 'normal'
    resolution = None
    stage = None
    status = 'open'
    superseder = None
    type = 'behavior'
    url = 'https://bugs.python.org/issue39407'
    versions = ['Python 3.7']
    

    Contributor guide

    Open the contributing guide

    First steps

    1. Read the whole issue, then the project's contributing guide.
    2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
    3. Fork the repository and make your change on a branch.
    4. Open a pull request that references the issue number.

    Research direction

    Start by running the attached python_struct_union_bug.py reproducer and then trace the ctypes implementation responsible for bitfield unions. Confirm the failure for bit widths greater than 8 bits and ensure the behavior is corrected without breaking the existing ctypes tests.

    Written by the indexing model from the issue text.

    Assessment

    Tech stack
    python
    Domain
    backend
    Issue type
    Bug
    Difficulty
    4/5
    Estimated time
    3-5 days
    Activity status
    Stale
    Clarity
    Mostly clear
    Newbie friendliness
    35/100

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