Assertion failure when marshalling buffer object with exception being set

[chgnrdv]

Bisected to 33d95c6. Appears only on debug builds, otherwise passes silently.

import marshal
x = ({int}, memoryview(b''))
marshal.dumps(x)

Output:

Fatal Python error: _Py_CheckSlotResult: Slot getbuffer of type memoryview succeeded with an exception set
Python runtime state: initialized
ValueError: unmarshallable object

Current thread 0x00007f213ea12280 (most recent call first):
  File "/home/radislav/repro.py", line 22 in <module>
Aborted (core dumped)

In w_complex_object, when PyMarshal_WriteObjectToString is called on set item that is unmarshallable (int type in this case), an exception gets set on current tstate. Attempt to marshal next tuple item that is memoryview instance leads to call to PyObject_GetBuffer with exception being set.

I'll submit a PR.

Linked PRs

• gh-106287: Improve error handling in marshalling code #106288
• gh-106287: do not write objects after an unmarshalling error #132715