Description

yuyichao

opened on May 1, 2025

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Documentation

The document for PyUnicode_InternFromString currently claimed that

CPython implementation detail: Strings interned this way are made immortal.

However, testing with simple code like,

        auto v = PyUnicode_InternFromString("abcdefg_aaaaa");
        // PyUnicode_InternImmortal(&v);
        printf("immortalized? %d\n", _Py_IsImmortal(v));

suggests that the returned value is not, which is expected based on the code since it calls _PyUnicode_InternMortal rather than _PyUnicode_InternImmortal. If a call to the internal API PyUnicode_InternImmortal was added (as in the commented out code above), then the string is indeed immortalized.

This document was added in #121364 but that PR did not change the behavior of this function. AFAICT, PyUnicode_InternFromString never immortalize the string ever since it was added in #120520.

The only public API that ever immortalized the input string appears to be PyUnicode_InternInPlace and that was changed in #121364 (the one that added the wrong doc) and there doesn't seem to be any public API that immortalize the string anymore. Although this is technically a document issue, I think it might be better to change the behavior of the function instead to match the document.

Linked PRs

• gh-133260: Remove claim that PyUnicode_InternFromString immortalizes #134213
• [3.14] gh-133260: Remove claim that PyUnicode_InternFromString immortalizes (GH-134213) #134883
• [3.13] gh-133260: Remove claim that PyUnicode_InternFromString immortalizes (GH-134213) #134884

Reacted by Kamil Monicz

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1. yuyichao

   added

   docsDocumentation in the Doc dirDocumentation in the Doc dir

   on May 1, 2025
2. github-project-automation

   added this to docs issueson May 1, 2025
3. github-project-automation

   moved this to Todo in docs issueson May 1, 2025
4. picnixz

   added

   topic-C-API

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   and removed

   docsDocumentation in the Doc dirDocumentation in the Doc dir

   on May 1, 2025
5. picnixz commented on May 4, 2025

   

   picnixz

   on May 4, 2025

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   Either it's a doc issue or it's an implementation issue. So I'll let both tags.
6. picnixz

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   docsDocumentation in the Doc dirDocumentation in the Doc dir

   on May 4, 2025
7. neonene commented on May 5, 2025

   

   neonene

   on May 5, 2025

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   cc @encukou
8. encukou

   added a commit that references this issue on May 19, 2025

   pythongh-133260: Remove claim that PyUnicode_InternFromString immorta…

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9. encukou commented on May 19, 2025

   

   encukou

   on May 19, 2025

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   Oh, good catch! Thanks! I did miss that in #121364 :/
   Given that 3.13 is in bugfix-only mode, I'll remove the docs note and backport that.

   @colesbury: PyUnicode_InternFromString can start immortalizing the string in main and possibly 3.14. Will it help free-threading?
10. encukou

    added a commit that references this issue on May 29, 2025

    gh-133260: Remove claim that PyUnicode_InternFromString immortalizes (G…

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11. miss-islington

    added 2 commits that reference this issue on May 29, 2025

    pythongh-133260: Remove claim that PyUnicode_InternFromString immorta…

    52f53f0

    pythongh-133260: Remove claim that PyUnicode_InternFromString immorta…

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12. encukou

    added 2 commits that reference this issue on May 29, 2025

    [3.14] gh-133260: Remove claim that PyUnicode_InternFromString immort…

    2d40dd0

    [3.13] gh-133260: Remove claim that PyUnicode_InternFromString immort…

    a9ba2ec
13. encukou commented on Jun 9, 2025

    

    encukou

    on Jun 9, 2025

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    The docs now allow either behaviour. Closing.
    Later we can make PyUnicode_InternFromString immortalize, if it's helpful.

    Thank you for the report, @yuyichao!
14. encukou

    closed this as completedon Jun 9, 2025
15. Pranjal095

    added a commit that references this issue on Jul 12, 2025

    pythongh-133260: Remove claim that PyUnicode_InternFromString immorta…

    defe241
16. taegyunkim

    added a commit that references this issue on Aug 4, 2025

    pythongh-133260: Remove claim that PyUnicode_InternFromString immorta…

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17. gostak-dd

    added a commit that references this issue on Jun 2, 2026

    pythongh-133260: Remove claim that PyUnicode_InternFromString immorta…

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