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Incorrect pointer alignment in _PyVectorcall_Function() of cpython/abstract.h #84233

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cryptomilk mannequin opened this issue Mar 24, 2020 · 7 comments
Closed

Incorrect pointer alignment in _PyVectorcall_Function() of cpython/abstract.h #84233

cryptomilk mannequin opened this issue Mar 24, 2020 · 7 comments
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3.8 only security fixes build The build process and cross-build topic-C-API

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@cryptomilk
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Mannequin

cryptomilk mannequin commented Mar 24, 2020

BPO 40052
Nosy @mcepl, @encukou, @eamanu, @miss-islington, @cryptomilk
PRs
  • bpo-40052: Fix alignment issue in PyVectorcall_Function() #19133
  • bpo-40052: Replace misaligned type casting with proper unions. #19179
  • bpo-40052: Fix alignment issue in PyVectorcall_Function() #23999
  • [3.9] bpo-40052: Fix alignment issue in PyVectorcall_Function() (GH-23999) #24005
  • [3.8] bpo-40052: Fix alignment issue in PyVectorcall_Function() (GH-23999) #24120
    		•

    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 2021-01-14.12:19:39.772>
created_at = <Date 2020-03-24.06:58:12.620>
labels = ['expert-C-API', 'build', '3.8']
title = 'Incorrect pointer alignment in _PyVectorcall_Function() of cpython/abstract.h'
updated_at = <Date 2021-01-14.12:19:39.771>
user = 'https://github.com/cryptomilk'

    bugs.python.org fields:

    activity = <Date 2021-01-14.12:19:39.771>
actor = 'petr.viktorin'
assignee = 'none'
closed = True
closed_date = <Date 2021-01-14.12:19:39.772>
closer = 'petr.viktorin'
components = ['C API']
creation = <Date 2020-03-24.06:58:12.620>
creator = 'asn'
dependencies = []
files = []
hgrepos = []
issue_num = 40052
keywords = ['patch']
message_count = 7.0
messages = ['364919', '364954', '364963', '364977', '384033', '384410', '384945']
nosy_count = 6.0
nosy_names = ['mcepl', 'petr.viktorin', 'python-dev', 'eamanu', 'miss-islington', 'asn']
pr_nums = ['19133', '19179', '23999', '24005', '24120']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue40052'
versions = ['Python 3.8']
    @cryptomilk
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    cryptomilk mannequin commented Mar 24, 2020

    In file included from /builds/cryptomilk/pam_wrapper/src/python/pypamtest.c:21:
    In file included from /usr/include/python3.8/Python.h:147:
    In file included from /usr/include/python3.8/abstract.h:837:
    /usr/include/python3.8/cpython/abstract.h:91:11: error: cast from 'char *' to 'vectorcallfunc *' (aka 'struct _object *(**)(struct _object *, struct _object *const *, unsigned long, struct _object *)') increases required alignment from 1 to 8 [-Werror,-Wcast-align]
    ptr = (vectorcallfunc*)(((char *)callable) + offset);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    1 error generated.

    The correct way to do it would be:

    union {
   char *data;
   vectorcallfunc *ptr;
} vc;
    vc.data = (char *)callable + offset;
return *vc.ptr;

    @cryptomilk cryptomilk mannequin added topic-C-API 3.8 only security fixes build The build process and cross-build labels Mar 24, 2020
    @eamanu
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    eamanu mannequin commented Mar 24, 2020

    Hi! I cannot reproduce the error. Could you provide the way to reproduce?

    thanks

    @cryptomilk
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    cryptomilk mannequin commented Mar 24, 2020

    clang -Werror -Wcast-align ...

    rpm -q clang9
    clang9-9.0.1-8.1.x86_64

    Does that help? Found in CI of

    https://gitlab.com/cwrap/pam_wrapper

    @cryptomilk
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    cryptomilk mannequin commented Mar 25, 2020

    I forgot, for detecting alignment issues or strict aliasing and this also falls under strict aliasing, you need to turn on optimizations.

    clang -O2 -Werror -Wcast-align ...

    @miss-islington
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    New changeset 056c082 by Petr Viktorin in branch 'master':
    bpo-40052: Fix alignment issue in PyVectorcall_Function() (GH-23999)
    056c082

    @encukou
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    encukou commented Jan 5, 2021

    New changeset 6e72ab9 by Miss Islington (bot) in branch '3.9':
    [3.9] bpo-40052: Fix alignment issue in PyVectorcall_Function() (GH-23999) (GH-24005)
    6e72ab9

    @encukou
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    encukou commented Jan 12, 2021

    New changeset 187f76d by Petr Viktorin in branch '3.8':
    [3.8] bpo-40052: Fix alignment issue in PyVectorcall_Function() (GH-23999) (GH-24120)
    187f76d

    @encukou encukou closed this as completed Jan 14, 2021
    @encukou encukou closed this as completed Jan 14, 2021
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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