[icanhasmath]

Summary

Backports upstream bpo-42825 (pythonGH-24098): Windows release builds now link with /OPT:REF,NOICF. The PR also bumps the version to 3.9.25.3.

The bug

On the Platform's Windows build of 3.9.25.2, + with an instance of a subclass of a built-in type returns NotImplemented instead of raising TypeError:

class I(int): pass
I(1) + "s"        # 3.9.25.2 Windows: NotImplemented; expected: TypeError

This also affects subclasses of datetime, date and timedelta, and it makes test_datetime's TestSubclassDateTime_Fast.test_computations fail.

Cause

• Objects/typeobject.c has two slot wrappers with identical bodies: wrap_binaryfunc and wrap_binaryfunc_l. update_one_slot() tells them apart by their address.
• The Windows builder now links with Visual Studio 2022 (MSC v.1944; 3.9.25 was built with v.1929). With identical-COMDAT folding on, that linker merges the two functions into one.
• With them merged, a heap subclass gets nb_add installed as its sq_concat too. PyNumber_Add then calls it as a fallback and returns its NotImplemented to the caller.
• Upstream fixed this in 3.10 by linking with /OPT:REF,NOICF. The commit message names these same two functions. 3.9 never got that change, while our 3.10 tags have it.

Evidence

• Platform build: reading wrapperbase.wrapper via ctypes shows int.__add__ and str.__add__ share a wrapper address on 3.9.25.2. On 3.9.25 and on 3.10.22.2 the addresses differ.
• Local builds on the EC2 Windows box, VS 2022 17.14, toolset v143:

Link options	I(1) + "s"	test_datetime
/OPT:REF,ICF, without this change	NotImplemented	—
with this change	TypeError	972 tests OK

• Windows regrtest: compared with 3.9.25, test_datetime was the only CPython regression in 3.9.25.2.

Release

After merge: tag v3.9.25.3, then add language/python 3.9.25.3 to the inventory and rebuild. The Windows QA suite then needs to re-run on the rebuilt runtime.

[ezequielp-activestate]

Approving. This is a clean backport and the diagnosis holds up.

• 38f8e73 is upstream b4af629 (bpo-42825, pythonGH-24098) with the same one-line PCbuild/pyproject.props change, character for character. Upstream's commit message names the same two functions (wrap_binaryfunc / wrap_binaryfunc_l).
• upstream/3.10 still carries /OPT:REF,NOICF today. Upstream only added /CGTHREADS:1 /PDBTHREADS:1 later for reproducible builds, which isn't needed for this fix.
• pythoncore.vcxproj imports pyproject.props, so the DLL that contains typeobject.c gets the flag. Nothing else in PCbuild sets EnableCOMDATFolding or another /OPT: value that would override it.
• The flag applies only to non-Debug builds, which is where ICF is on.
• The version bump has the same shape as the 3.9.25.2 one: PY_VERSION plus a whatsnew section.

I couldn't build on Windows here, so the behavior check relies on your before/after table. A useful check after the rebuild: class I(int): pass; I(1) + "s" raises TypeError and test_datetime passes.