`co_lnotab` must be removed in 3.12 according to PEP 626

[sobolevn]

The co_lnotab attribute will be deprecated in 3.10 and removed in 3.12.

https://peps.python.org/pep-0626/#backwards-compatibility

It was documented as deprecated in 3.10 and to-be-removed in 3.12: https://docs.python.org/3/whatsnew/3.10.html#pep-626-precise-line-numbers-for-debugging-and-other-tools

Original issue: #86412

Right now CPython does not use co_lnotab in its source code.
But, there are two mentions of it:

1. In gdb:

   cpython/Misc/gdbinit

   Lines 60 to 61 in 6ef6915

   	set $__sz = ((PyVarObject *)$__co->co_lnotab)->ob_size/2
   	set $__p = (unsigned char *)((PyBytesObject *)$__co->co_lnotab)->ob_sval

   And I have no idea how it works! Some weird mix of C and some kind of a DSL / scripting language
2. In clinic.test:

   cpython/Lib/test/clinic.test

   Line 3575 in 6ef6915

   co_lnotab: PyBytesObject(c_default="(PyBytesObject *)self->co_lnotab") = None

   But, this is just a string-based test. So, I think it can stay there

If that's fine - I would like to do the honours.

CC @markshannon

Linked PRs

• gh-101865: Deprecate co_lnotab from code objects as per PEP 626 #101866
• gh-101865: Docs: Keep co_lnotab deprecation for at least 3.14 #126392
• [3.13] gh-101865: Docs: Keep co_lnotab deprecation for at least 3.14 (GH-126392) #126403
• [3.12] gh-101865: Docs: Keep co_lnotab deprecation for at least 3.14 (GH-126392) #126404

[markshannon]

I don't get any warning when using co_lnotab in 3.11, so I don't think we can remove it yet.
Don't assume everyone has read PEP 626.

We should at least warn when using it for a couple of versions, before removing it.

It isn't causing us any problems either, so there is not rush to remove it. It can wait for 3.14 or so.

[sobolevn]

Ok then, so DeprecationWarning it is! 👍