CC@Fidget-Spinner@colesbury@sergey-miryanov

If this PR will be merged we can removePyStackRef_FromPyObjectStealMortal at all.
OTOH, I'd like to provide this change in a separate PR.

This is another attempt to provide the same StackRef flagging scheme for all builds (GIL, FT, STACKREF_DEBUG). Instead of adding_Py_IsImmortal check toPyStackRef_FromPyObjectSteal for FR builds as in#141675, we make no checks at all in this function. As a result, immortal objects will be DECREF'ed with no effect at reference closing.

• Issue:Add tests on basicPyStackRef functions #139716

We can't rely on Py_DECREF to do the immortal check, as that is more expensive than simply checking a bit on a pointer. You have to do an atomic read of memory now.

We can't rely on Py_DECREF to do the immortal check, as that is more expensive than simply checking a bit on a pointer. You have to do an atomic read of memory now.

It seems that I'm not quite understand, when we will do additional atomic reads.
Do you mean FT builds? For those nothing changes sincePy_DECREF_MORTAL isPy_DECREF on them.
And there's no atomic reads atPy_DECREF on GIL builds.

Sorry I think I'm misunderstanding. This PR moves the immortal check from the stackref to the Py_DECREF right?

Sorry I think I'm misunderstanding. This PR moves the immortal check from the stackref to the Py_DECREF right?

Yes. If we steal stack reference from the immortal object then there will be no actual decrefing atPy_DECREF.