Implement Py_UNUSED() for Windows MSVC compiler

[vstinner]

The Py_UNUSED() is not implemented for the Windows MSVC compiler.

Example with this function included by Python.h: see #107239 (comment)

static inline unsigned int
PyUnicode_IS_READY(PyObject* Py_UNUSED(op))
{ return 1; }

Without my change, building a C program with cl /W4 which just includes Python.h emits the warning:

Include\cpython/unicodeobject.h(199): warning C4100: '_unused_op': unreferenced formal parameter

With my change, no warnings are emitted!

Linked PRs

• gh-107249: Implement Py_UNUSED() for MSVC #107250
• [3.12] gh-107249: Implement Py_UNUSED() for MSVC (GH-107250) #127907