gh-111178: Generate correct signature for self converters

[erlend-aasland]

• Issue: UBSan: Calling a function through pointer to incorrect function type is undefined behavior #111178

[erlend-aasland]

WDYT, @picnixz?

[picnixz]

I think this is what I had in mind. I'm no more on my dev session but I'll pick your branch, create a branch with all my known UBSan fixes branches and then I'll need to manually address the remaining ones.

AFAICT, no new _impl functions were added so performances shouldn't be affected I think? (it's only pointer casts for the compiler). I'll review more in details tomorrow but thank you for the work!

[erlend-aasland]

Yeah, this PR only makes sure we're using PyObject pointers in the PyMethodDef "entries". No new [clinic input] sections, no new _impl functions. Performance should not be affected.

[erlend-aasland]

I'll leave this in draft so we don't create a review rush.