TraceRefs build triggers assertion errors

[Yhg1s]

In a --with-trace-refs --with-pydebug build of 3.12 and main, even a simple test like test_int triggers an assertion error in the refchain handling. I expect it's caused by @ericsnowcurrently's PR #107567.

cpython-tracerefs % ../../cpython/configure -C --with-trace-refs --with-pydebug
[...]
cpython-tracerefs % make
[...]
cpython-tracerefs % ./python -m test test_int
0:00:00 load avg: 2.79 Run tests sequentially
0:00:00 load avg: 2.79 [1/1] test_int

== Tests result: SUCCESS ==

1 test OK.

Total duration: 477 ms
Tests result: SUCCESS
../../cpython/Objects/object.c:2234: _Py_ForgetReference: Assertion failed: invalid object chain
Enable tracemalloc to get the memory block allocation traceback

object address  : 0x7ff86d998050
object refcount : 0
object type     : 0x55fbc49aba60
object type name: dict
object repr     : <refcnt 0 at 0x7ff86d998050>

Fatal Python error: _PyObject_AssertFailed: _PyObject_AssertFailed
Python runtime state: finalizing (tstate=0x000055fbc4b27e88)

Current thread 0x00007ff86daec740 (most recent call first):
  <no Python frame>
Aborted

Linked PRs

• [3.12] gh-107630: Revert "[3.12] gh-107080: Fix Py_TRACE_REFS Crashes Under Isolated Subinterpreters (gh-107567) (#107599)" #107648
• gh-107630: Initialize Each Interpreter's refchain Properly #107733
• [3.12] gh-107080: Fix Py_TRACE_REFS Crashes Under Isolated Subinterpreters #107737
• gh-107630: Fix Remaining Subinterpreters Crashes on Py_TRACE_REFS Builds #107750

[Yhg1s]

FWIW, if the fix for this is too involved or too complicated, I'd rather roll back #107567 and leave tracerefs broken when using isolated subinterpreters than leaving tracerefs broken for everything.

[ericsnowcurrently]

I'm okay with a revert on 3.12. You're right that the previous state of affairs was better.

FWIW, there's an object leaking between interpreters somewhere and tracking that down is a big pain. I don't know how long it will take, so reverting now makes sense. I would like to un-revert once I've tracked down the culprit though.

[sunmy2019]

Confirmed it is fixed on the 3.12 branch. The issue would remain open for the main branch.

[ericsnowcurrently]

Once gh-107751 lands, this can be closed.