Add offsets for dict introspection to _Py_DebugOffsets

[charles-dyfis-net]

Feature or enhancement

Proposal:

To use _Py_DebugOffsets to perform version-independent read-only introspection of a Python process, struct offsets are required that aren't currently exposed:

• tp_dictoffset -- where the dict pointer lives
• tp_basicsize -- where inline values start
• ht_cached_keys -- key ordering for inline values in heap types

The immediately motivating use case is implementing py-spy (read-only sampling profiler) support for Python 3.14 without continuing the prior practice of shipping bindgen wrappers for each supported version; dict introspection is required to read thread names from threading._active[tid]._name (which also requires looking through sys.modules to find the threading module), and for implementing --dump-locals.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

[picnixz]

cc @pablogsal (idk if this feature needs a pre-discussion)

[pablogsal]

It doesn't need discussion as is a good idea but we cannot backport this to 3.14 it would be 3.15 only

[pablogsal]

I will do it today