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GeezerVison is showing github.com — bpo-1635741: Fix unicode_dealloc() for mortal interned string by vstinner · Pull Request #21270 · python/cpython

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@vstinner

@vstinner vstinner commented Jul 1, 2020 •
edited by bedevere-bot
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When unicode_dealloc() is called on a mortal interned string, the
string reference counter is now reset at zero, rather than leaking
one reference.

https://bugs.python.org/issue1635741

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@vstinner
bpo-1635741: Fix unicode_dealloc() for mortal interned string
6bf611c 
When unicode_dealloc() is called on a mortal interned string, the
string reference counter is now reset at zero, rather than leaking
one reference.
@vstinner vstinner added the skip news label Jul 1, 2020
@the-knights-who-say-ni the-knights-who-say-ni added the CLA signed label Jul 1, 2020
@bedevere-bot bedevere-bot added the awaiting core review label Jul 1, 2020
@vstinner

vstinner commented Jul 1, 2020

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cc @shihai1991 @pablogsal
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shihai1991
shihai1991 reviewed Jul 2, 2020
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Comment thread Objects/unicodeobject.c
PyDict_DelItem(). */
assert(Py_REFCNT(unicode) == 0);
Py_SET_REFCNT(unicode, 3);
if (PyDict_DelItem(interned, unicode) != 0) {

@shihai1991 shihai1991 Jul 2, 2020

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Can we skip PyDict_DelItem() and set interned unicode's refcnt = 0 directly in here?

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@vstinner vstinner Jul 2, 2020

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We cannot remove the PyDict_DelItem() call.

PyUnicode_InternInPlace() uses black magic: it ignores 2 references (key and value) of the interned dictionary.

We must remove the string from the interned dictionary. Otherwise, the dictionary will contain a dangling pointer when unicode_dealloc() completes: using the dict is likely to crash in this case.

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@shihai1991 shihai1991 Jul 2, 2020

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got it, make sense, thanks.

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shihai1991
shihai1991 approved these changes Jul 2, 2020
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Thanks victor's PR, LGTM :)

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@vstinner
vstinner merged commit 3549ca3 into python:master Jul 3, 2020
@bedevere-bot bedevere-bot removed the awaiting core review label Jul 3, 2020
@vstinner
vstinner deleted the unicode_dealloc branch July 3, 2020 14:59
@vstinner

vstinner commented Jul 3, 2020

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Technically, this change is mostly a cleanup, since the object is destroyed anyway a few lines below.
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@kylotan kylotan mannequin mentioned this pull request Sep 19, 2022
Py_Finalize() doesn't clear all Python objects at exit #44470
Closed
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@shihai1991 shihai1991 shihai1991 approved these changes

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@vstinner @shihai1991 @the-knights-who-say-ni @bedevere-bot
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