ctypes: Deprecate SetPointerType() and ARRAY() functions

[vstinner]

The ctypes module has two undocumented functions: SetPointerType() and ARRAY(). These functions are marked as XXX Deprecated, but only in comments.

I propose to deprecate ctypes.SetPointerType() and ctypes.ARRAY() by emitting a DeprecationWarning warning.

These functions are not documented and not used in Python, but there are tested.

Linked PRs

• gh-105733: Deprecate ctypes SetPointerType() and ARRAY() #105734
• gh-105733: Fix ctypes What's New entry #106576
• gh-105733: Soft-deprecate ctypes.ARRAY, rather than hard-deprecating it. #122281
• [3.13] gh-105733: Soft-deprecate ctypes.ARRAY, rather than hard-deprecating it. (GH-122281) #122440

[encukou]

I disagree with the proposal. (And with taking one hour between a proposal and merge.)

The plan to remove ARRAY in 3.15 goes against PEP 387:

If the expected maintenance overhead and security risk of the deprecated behavior is small (e.g. an old function is reimplemented in terms of a new, more general one), it can stay indefinitely (or until the situation changes).

(I'll note that this clarification got added a few days after this proposal, though.)

The function is two lines long, and has tests. It has no maintenance overhead or additional security risk.
It's also used in third-party projects (some of which test with alphas/betas and have now switched to multiplication).

I propose to restore it and soft-deprecate instead. Would you be OK with that, @vstinner?

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As for SetPointerType, yeah, no one should be using that, and hardly anyone is.

[encukou]

(anecdotally: at EuroPython I've seen a person use ARRAY in the REPL. This is not worth them re-learning how to make array types.)