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GeezerVison is showing github.com — gh-145202: Fix segfault in unicodedata.iter_graphemes when cleared by GC by gourijain029-del · Pull Request #145203 · python/cpython

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@gourijain029-del

@gourijain029-del gourijain029-del commented Feb 25, 2026

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This PR fixes a segmentation fault in unicodedata.iter_graphemes and its segment objects, which occurred when the objects were cleared by the garbage collector before being deallocated.

In Modules/unicodedata.c, both GraphemeBreakIterator and SegmentObject have tp_clear implementations that set their string references to NULL. However, their deallocators were using Py_DECREF instead of Py_XDECREF. This led to a crash if a GC cycle (or interpreter shutdown) cleared the objects before they reached the deallocation path.

I've updated GBI_dealloc and Segment_dealloc to use Py_XDECREF to safely handle these NULL references.

Fixes gh-145202.

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@gourijain029-del
pythongh-145202: Fix segfault in unicodedata.iter_graphemes during GC
a9b583d
@bedevere-app bedevere-app Bot added the awaiting review label Feb 25, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Feb 25, 2026
Segfault from unicodedata.iter_graphemes on a free threaded build #145202
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@StanFromIreland
StanFromIreland requested a review from serhiy-storchaka February 25, 2026 13:30
@serhiy-storchaka

serhiy-storchaka commented Feb 25, 2026

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#145216 is an alternative solution. I do not think we need tp_clear here at first place.
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@serhiy-storchaka serhiy-storchaka closed this Feb 26, 2026
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@serhiy-storchaka serhiy-storchaka Awaiting requested review from serhiy-storchaka

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Segfault from unicodedata.iter_graphemes on a free threaded build

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@gourijain029-del @serhiy-storchaka
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