Description

smontanaro

opened on Oct 28, 2026

Issue body actions

Bug report

The HAVE_PROTOTYPES macro disappeared recently (commit e4f7327c). While it's not used in Python proper, it seems to be used by some third-party packages. Removing it seems short-sighted. Without it, the pillow package fails to build, because it requires ANSI prototypes and no longer thinks Python provides them.

CPython versions tested on:

3.16

Operating systems tested on:

macOS

Activity

1. smontanaro

   added

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

   on Oct 28, 2026
2. smontanaro commented on Oct 28, 2026

   

   smontanaro

   on Oct 28, 2026

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   @methane @emmatyping
3. NekoAsakura

   added

   buildThe build process and cross-buildThe build process and cross-build

   on Oct 28, 2026
4. hugovk commented on Oct 28, 2026

   

   hugovk

   on Oct 28, 2026

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   Don't worry about Pillow, we've (this week!) already removed HAVE_PROTOTYPES and STDC_HEADERS, they were added 30 years ago and are no longer needed.

   • Remove HAVE_PROTOTYPES and STDC_HEADERS checks python-pillow/Pillow#10324
   • cp316 drops required macro for Pillow to compile python-pillow/Pillow#10323

   If it shows up in other libraries, let's see if they can also remove them. The alpha period is the right time for this, and we can always restore later on if it's really necessary.

   Reacted by Skip Montanaro and Emma Smith

   Reacted by Inada Naoki
5. smontanaro commented on Oct 28, 2026

   

   smontanaro

   on Oct 28, 2026

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   Thanks @hugovk. So I should be able to just reference the Pillow repo for the time being?
6. picnixz

   added

   extension-modulesC modules in the Modules dirC modules in the Modules dir

   3.16new features, bugs and security fixesnew features, bugs and security fixes

   and removed

   extension-modulesC modules in the Modules dirC modules in the Modules dir

   on Oct 28, 2026
7. Keith-S-Thompson commented on Oct 28, 2026

   

   Keith-S-Thompson

   on Oct 28, 2026

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   I don't see a commit e4f7327c. The relevant commit seems to be b26fc41.
8. hugovk commented on Oct 29, 2026

   

   hugovk

   on Oct 29, 2026

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   5. Thanks @hugovk. So I should be able to just reference the Pillow repo for the time being?

   Yes, I think so. Prototypes are C89, long required: https://peps.python.org/pep-0007/#c-standards

   From what I can tell, the oldest Python that no longer needs this macro is 2.0: if a compiler can't handle prototypes, it can't compile Python.h from 2.0 onwards. So if your library (somehow!) supports Python 2.0 up to 3.16, it's fine with these removals.

   Python 1.6 is the last release that needs this macro. So if your library (somehow!!!) supports Python 1.6 up to 3.16, then the macro is needed. I doubt there are any, and we don't need to support them :)

   Reacted by Emma Smith
9. hugovk

   added

   pendingThe issue will be closed if no feedback is providedThe issue will be closed if no feedback is provided

   on Oct 29, 2026

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