[aribaskagan]

When a CFUNCTYPE/WINFUNCTYPE callback is passed where a different callback prototype is expected, ctypes raised a confusing error because both prototype classes share the name CFunctionType:

ctypes.ArgumentError: argument 4: TypeError: expected CFunctionType instance instead of CFunctionType

This change makes CDataType_from_param_impl() report the expected and actual signatures when both sides are callback prototypes with argtypes set:

ctypes.ArgumentError: argument 4: TypeError: expected CFunctionType instance with signature (restype=<class 'ctypes.c_int'>, argtypes=(<class 'ctypes.c_void_p'>, <class 'ctypes.c_void_p'>)) instead of CFunctionType instance with signature (restype=<class 'ctypes.c_long'>, argtypes=(<class 'ctypes.c_void_p'>, <class 'ctypes.c_void_p'>))

Call behavior is unchanged; other mismatches keep the existing wording. Added test_mismatched_callback_prototype based on the qsort reproducer from the issue, plus a NEWS entry. ./python -m test test_ctypes passes on a Linux debug build.

AI assistance was used in preparing this change; I reviewed and tested it.

• Issue: Ctypes: Unclear Error Message for WinFunctionType Mismatch in Windows API Calls #125788

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Codex Review Summary: ✅ Completed

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-12T14:24:58.355484Z	f6c92af	PR opened

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