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GeezerVison is showing github.com — PY_SSIZE_T_MIN negate UB in unicode_format.c and bytesobject.c · Issue #151847 · python/cpython

PY_SSIZE_T_MIN negate UB in unicode_format.c and bytesobject.c #151847

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PY_SSIZE_T_MIN negate UB in unicode_format.c and bytesobject.c#151847
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interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

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@aisk
aisk
opened on Jun 21, 2026
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Bug report

Bug description:

Original gist: https://gist.github.com/devdanzin/577421b083bad6802aa391b909d1a725

unicode_format_arg_parse (line 563): -PY_SSIZE_T_MIN is undefined behavior in C. Benign on two's-complement but technically UB. bytesobjects.c have the same problem.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

  • gh-151847: Avoid undefined behaviour negating PY_SSIZE_T_MIN width in str/bytes formatting #151849

Activity

  1. aisk
    added a parent issue on Jun 21, 2026
    • Umbrella issue: bugs found using cpython-review-toolkit #146102
  2. aisk
    added
    type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error
    on Jun 21, 2026
  3. picnixz
    added
    interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)
    on Jun 21, 2026
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    interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

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