[Python-Dev] subtype_dealloc causes segfaults on c heap type subclasses

Hi everyone, I found a bug in subtype_dealloc causing segfaults when used with C heap types. Given that it modifies the deallocation routine of every instance, I thought it was important to surface this in here as well. Also worth noting, this blocks the adoption of PEP384 in C Extension modules that depend on subclassable types. The bug and the fix are explained in detail in the PR: https://github.com/python/cpython/pull/15323