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signal module wrongly relies on small int singletons #90566

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tiran opened this issue Jan 17, 2022 · 3 comments
Closed

signal module wrongly relies on small int singletons #90566

tiran opened this issue Jan 17, 2022 · 3 comments
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3.9 only security fixes 3.10 only security fixes 3.11 only security fixes extension-modules C modules in the Modules dir type-bug An unexpected behavior, bug, or error

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@tiran
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tiran commented Jan 17, 2022

BPO 46408
Nosy @tiran, @serhiy-storchaka
Superseder
  • bpo-23325: Turn SIG_DFL and SIG_IGN into functions
    		•

    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 = <Date 2022-01-17.09:13:13.899>
created_at = <Date 2022-01-17.09:01:28.784>
labels = ['extension-modules', 'type-bug', '3.9', '3.10', '3.11']
title = 'signal module wrongly relies on small int singletons'
updated_at = <Date 2022-01-17.09:13:40.107>
user = 'https://github.com/tiran'

    bugs.python.org fields:

    activity = <Date 2022-01-17.09:13:40.107>
actor = 'christian.heimes'
assignee = 'none'
closed = True
closed_date = <Date 2022-01-17.09:13:13.899>
closer = 'christian.heimes'
components = ['Extension Modules']
creation = <Date 2022-01-17.09:01:28.784>
creator = 'christian.heimes'
dependencies = []
files = []
hgrepos = []
issue_num = 46408
keywords = []
message_count = 3.0
messages = ['410747', '410748', '410750']
nosy_count = 2.0
nosy_names = ['christian.heimes', 'serhiy.storchaka']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '23325'
type = 'behavior'
url = 'https://bugs.python.org/issue46408'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']
    @tiran
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    tiran commented Jan 17, 2022

    The signal.signal() function directly compares PyObject *handler with PyObject *modstate->ignore_handler. This works on most platforms because they are both small ints and Python uses singletons for cached small ints.

    The assumption breaks when Python is built without small int cache or a platform has SIG_IGN / SIG_DFL that is outside the range of small int cache. The wasm32-emscripten platform uses "((void (*)(int))-2)" (4294967294) for SIG_IGN. The wrong comparison breaks several tests on WASM32. The function should use PyObject_RichCompareBool(handler, modstate->ignore_handler, Py_EQ) instead.

        if (handler == modstate->ignore_handler) {
        func = SIG_IGN;
    }
    else if (handler == modstate->default_handler) {
        func = SIG_DFL;
    }

    cpython/Modules/signalmodule.c

    Lines 530 to 534 in 7f4b69b

    if (handler == modstate->ignore_handler) {
    func = SIG_IGN;
    }
    else if (handler == modstate->default_handler) {
    func = SIG_DFL;

    @tiran tiran added 3.9 only security fixes 3.10 only security fixes 3.11 only security fixes extension-modules C modules in the Modules dir type-bug An unexpected behavior, bug, or error labels Jan 17, 2022
    @serhiy-storchaka
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    See msg234768 and bpo-23325. I propose to close this as a duplicate of bpo-23325.

    @tiran tiran closed this as completed Jan 17, 2022
    @tiran tiran closed this as completed Jan 17, 2022
    @tiran
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    tiran commented Jan 17, 2022

    Yes, it's a duplicate.

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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