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warning: dereferencing type-punned pointer will break strict-aliasing rules #72304

Closed as not planned
Closed as not planned
warning: dereferencing type-punned pointer will break strict-aliasing rules#72304
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3.7 (EOL)end of lifebuildThe build process and cross-buildextension-modulesC modules in the Modules dir

Description

@serhiy-storchaka
serhiy-storchaka
opened on Sep 13, 2016
BPO 28117
Nosy @mdickinson, @tiran, @serhiy-storchaka, @ma8ma, @ekul00
Dependencies
  • bpo-16113: Add SHA-3 and SHAKE (Keccak) support
    		•
    Files
  • keccak_warnings.patch
    		•

    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 2016-09-13.07:11:54.190>
labels = ['extension-modules', 'build', '3.7']
title = 'warning: dereferencing type-punned pointer will break strict-aliasing rules'
updated_at = <Date 2018-09-26.10:24:44.124>
user = 'https://github.com/serhiy-storchaka'

    bugs.python.org fields:

    activity = <Date 2018-09-26.10:24:44.124>
actor = 'ekul'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Extension Modules']
creation = <Date 2016-09-13.07:11:54.190>
creator = 'serhiy.storchaka'
dependencies = ['16113']
files = ['44847']
hgrepos = []
issue_num = 28117
keywords = ['patch']
message_count = 5.0
messages = ['276193', '276210', '277546', '306005', '326439']
nosy_count = 5.0
nosy_names = ['mark.dickinson', 'christian.heimes', 'serhiy.storchaka', 'masamoto', 'ekul']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue28117'
versions = ['Python 3.6', 'Python 3.7']

    Activity

    1. serhiy-storchaka commented on Sep 13, 2016

      @serhiy-storchaka
      serhiy-storchaka
      on Sep 13, 2016
      MemberAuthor

      In file included from /home/serhiy/py/cpython/Modules/_sha3/sha3module.c:113:0:
      /home/serhiy/py/cpython/Modules/_sha3/kcp/KeccakP-1600-inplace32BI.c: In function ‘_PySHA3_KeccakP1600_SetBytesInLaneToZero’:
      /home/serhiy/py/cpython/Modules/_sha3/kcp/KeccakP-1600-inplace32BI.c:97:5: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
      low = *((UINT32*)(laneAsBytes+0));
      ^
      In file included from /home/serhiy/py/cpython/Modules/_sha3/sha3module.c:113:0:
      /home/serhiy/py/cpython/Modules/_sha3/kcp/KeccakP-1600-inplace32BI.c: In function ‘_PySHA3_KeccakP1600_AddBytesInLane’:
      /home/serhiy/py/cpython/Modules/_sha3/kcp/KeccakP-1600-inplace32BI.c:152:5: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
      low = *((UINT32*)(laneAsBytes+0));
      ^
      /home/serhiy/py/cpython/Modules/_sha3/kcp/KeccakP-1600-inplace32BI.c: In function ‘_PySHA3_KeccakP1600_ExtractBytesInLane’:
      /home/serhiy/py/cpython/Modules/_sha3/kcp/KeccakP-1600-inplace32BI.c:296:5: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
      *((UINT32*)(laneAsBytes+0)) = low;
      ^
      /home/serhiy/py/cpython/Modules/_sha3/kcp/KeccakP-1600-inplace32BI.c: In function ‘_PySHA3_KeccakP1600_ExtractAndAddBytesInLane’:
      /home/serhiy/py/cpython/Modules/_sha3/kcp/KeccakP-1600-inplace32BI.c:369:5: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
      *((UINT32*)(laneAsBytes+0)) = low;
      ^

    2. serhiy-storchaka
      added
      3.7 (EOL)end of life
      extension-modulesC modules in the Modules dir
      buildThe build process and cross-build
      on Sep 13, 2016

    3. tiran commented on Sep 13, 2016

      @tiran
      tiran
      on Sep 13, 2016
      Member

      The compile warning occurs on 32bit builds only: http://buildbot.python.org/all/builders/x86%20Gentoo%20Non-Debug%20with%20X%203.x

    4. serhiy-storchaka commented on Sep 27, 2016

      @serhiy-storchaka
      serhiy-storchaka
      on Sep 27, 2016
      MemberAuthor

      Proposed patch eliminates warnings.

    5. ma8ma commented on Nov 10, 2017

      @ma8ma
      ma8mamannequin
      on Nov 10, 2017
      Mannequin

      Serhiy, would you open a PR? Your patch looks good to me.
      I've been looking at the warning on my machine (ubuntu 16.04 x86), it's a bit annoying to me.

    6. ekul00 commented on Sep 26, 2018

      @ekul00
      ekul00mannequin
      on Sep 26, 2018
      Mannequin

      I just got this set of warnings while building 3.6.6 on RasPi Debian9/ARM. Good to know the warning is spurious.

      Just finding my way here - is Serhiy's patch above a working 2016 fix for this that got stuck in review? I couldn't find a PR for it. If the warning _is_ spurious it would be great to patch it.

    7. ezio-melotti
      transferred this issue fromon Apr 10, 2022

    8. serhiy-storchaka commented on Aug 5, 2026

      @serhiy-storchaka
      serhiy-storchaka
      on Aug 5, 2026
      MemberAuthor

      Modules/_sha3/kcp/ no longer exists: the Keccak Code Package was replaced with tiny_sha3 in bpo-47098 (GH-32060), and SHA-3 is now implemented with HACL*. The warning is gone with the code that caused it.

    9. serhiy-storchaka
      closed this as not plannedon Aug 5, 2026
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