gh-151515: Fix incorrect function pointer cast in asdl_c.py generator

[CoderSilicon]

Summary

This PR fixes an undefined behavior bug in the C code generated by Parser/asdl_c.py for get_ast_state().

The Problem

In the generated code, _PyOnceFlag_CallOnce is invoked like this:
_PyOnceFlag_CallOnce(&state->once, (_Py_once_fn_t *)&init_types, state)

Using &init_types passes a pointer to a function pointer (effectively a double pointer), rather than the function pointer itself. by forcing this with an explicit cast (_Py_once_fn_t *) silences the compiler but triggers a strict aliasing violation and undefined behavior at runtime when the pointer is dereferenced. This can lead to compiler-optimization-driven segmentation faults, particularly in free-threaded/GIL-disabled builds where one-time initialization flags are heavily relied upon.

The Fix

Updated Parser/asdl_c.py to pass init_types directly with a standard function pointer cast (_Py_once_fn_t)init_types (removing the extra & and *). Ran make regen-ast to cleanly update the generated files.

• Issue: gh-151515 Fix incorrect function pointer cast in asdl_c.py generator #151515

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[picnixz]

Plsease revert all cosmetic changes in this PR. Only change the part that may need to change.

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[CoderSilicon]

I have made the requested changes and applied the requested suggestions; please review again

[chris-eibl]

I don’t see how the original code produces undefined behaviour. However, why not just remove the cast?

I agree with @vadmium, I do not see undefined behaviour here and the cast could be removed.

All other occurences of _PyOnceFlag_CallOnce do not use the cast either, since their fn argument matches (like in this case).

I am unsure whether that removal is worth a PR. At best +0 from me ...

[chris-eibl]

@CoderSilicon : to get CI green, you'll need to run make regen-ast again ...

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