PyUnstable_Eval_RequestCodeExtraIndex freefunc may be called with a null pointer

Bug report

Bug description:

The PyUnstable_Code_SetExtra path checks for the previous value being null but code_dealloc does not.

This can lead to freefunc being called with null either through the extra value being explicitly set to null or through a value being set on an extra value with a later index, without a value being set on an earlier index.

This doesn't match the documentation, which says that freefunc is not called for null values.

CPython versions tested on:

3.11, CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-122492

Objects/codeobject.c の PyUnstable_Code_SetExtra のチェックと、報告でリンクされている code_dealloc パスから始めてください。両方のパスを、null 値に関する文書化された動作と比較し、その後、すでに進行中の作業とその検証アプローチについて、リンクされている PR gh-122492 を調べてください。