[3.13] gh-121794: Don't set ob_tid to zero in fast-path dealloc (GH-121799)
#121821
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…honGH-121799) We should maintain the invariant that a zero `ob_tid` implies the refcount fields are merged. * Move the assignment in `_Py_MergeZeroLocalRefcount` to immediately before the refcount merge. * Update `_PyTrash_thread_destroy_chain` to set `ob_ref_shared` to `_Py_REF_MERGED` when setting `ob_tid` to zero. Also check this invariant with assertions in the GC in debug builds. That uncovered a bug when running out of memory during GC. (cherry picked from commit d23be39) Co-authored-by: Sam Gross <colesbury@gmail.com>
This was referenced Jul 15, 2024
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We should maintain the invariant that a zero
ob_tidimplies therefcount fields are merged.
_Py_MergeZeroLocalRefcountto immediatelybefore the refcount merge.
_PyTrash_thread_destroy_chainto setob_ref_sharedto_Py_REF_MERGEDwhen settingob_tidto zero.Also check this invariant with assertions in the GC in debug builds.
That uncovered a bug when running out of memory during GC.
(cherry picked from commit d23be39)
Co-authored-by: Sam Gross colesbury@gmail.com
_Py_MergeZeroLocalRefcountshould not setob_tidto zero in fast-path dealloc #121794