Hey Victor
First of all, I would like to thank Victor for all his efforts to resolve
this issue.
And I want to thank the other contributors to this issue as well!
I am very happy to hear that we can close bpo-1635741.
This has been a long mission requiring patience and
I'm proud to finally be able to put an end to it.
Let's move forward to the next step!
Warm regards,
Dong-hee
2022년 1월 28일 (금) 오전 12:37, Victor Stinner 님이 작성:
> Hi,
>
> tl; dr Python no longer leaks memory at exit on the "python -c pass"
> command ;-)
>
>
> == Bug report ==
>
> In 2007, the bpo-1635741 issue was reported on SourceForge:
> "Interpreter seems to leak references after finalization".
>
> This bug is 15 years old. It saw the bugs migration from SourceForge
> to Roundup (bugs.python.org) in 2007, the code migration from
> Subversion to Mercurial in 2009, and the second code migration from
> Mercurial to Git in 2016!
>
> Link to the main issue: https://bugs.python.org/issue1635741
>
> Some people reported similar issues seen by WinCRT debug (bpo-6741),
> MSVC Debug C Runtime (bpo-32026), GCC AddressSanitzer (bpo-26888), or
> LeakSanitizer and Valgrind (bpo-21387).
>
> In general, "leaking memory" at Python exit doesn't matter, since the
> operating system releases all memory when a process completes. It
> matters when Python is embedded in an application. For example, Python
> can be used by a plugin which is unloaded and reloaded multiple times.
> It also matters for sub-interpreters.
>
>
> == Tedious task ==
>
> In the last 3 years, many people helped fixing this old issue by
> converting static types to heap types, adding a module state to C
> extension modules, converting extensions to the multi-phase
> initialization API (PEP 489), fix many memory leaks, fix bugs, etc.
>
> When it became possible to cleanly unload an extension module (thanks
> for the multi-phase init), tests on sub-intepreters (which load and
> unload extension modules) showed many *old* reference leaks: all of
> them have been fixed! When a test is run in sub-interpreters, Python
> is able to detect leaks, whereas currently it doesn't check for memory
> leaks at Python exit.
>
>
> == Python 3.10 regressions ==
>
> During the Python 3.10 development, we identified and fixed 3 major
> regressions caused by this work:
>
> * Converting static types to heap types make them mutable: the
> Py_TPFLAGS_IMMUTABLETYPE flag was added; 68 types use it in Python
> 3.11 (bpo-43908).
>
> * It became possible to create uninitialized objects by instanciating
> types (which should not be instanciated directly): the
> Py_TPFLAGS_DISALLOW_INSTANTIATION was added; 41 types use it in Python
> 3.11 (bpo-43916). For example, you cannot create an instance of
> type(sys.flags).
>
> * Heap types must implement the full GC protocol: Py_TPFLAGS_HAVE_GC
> flag, traverse and clear functions. Otherwise, the GC is unable to
> break reference cycles, whereas a type contains (multiple) strong
> references to itself (in the MRO tuple and in methods). All heap types
> have been fixed to fully implement the GC protocol (bpo-40217).
>
>
> == PEPs ==
>
> The work relies on multiple PEPs:
>
> * PEP 489: Multi-phase extension module initialization
> * PEP 573: Module State Access from C Extension Methods
> * PEP 630: Isolating Extension Modules
>
>
> == Persons who helped fixing the issue ==
>
> Incomplete list of people who helped to fix this issue:
>
> * Christian Heimes (modules: symtable, _hashlib, ,_random, grp, pwd,
> _queue, spwd, _struct, gc, _posixshmem, _posixsubprocess, select,
> resource)
> * Dong-hee Na (modules: _statistics, itertools, _heapq, _collections,
> _uuid, math, _stat, syslog, errno, fcntl, mmap, _dbm, _gdbm, _lzma,
> faulthandler, _bisect)
> * Eric Snow (PEP 573)
> * Erlend Egeberg Aasland (modules: _sqlite3, _sre, _multibytecodec)
> * Hai Shi (modules: _json, _codecs, _crypt, _contextvars, _abc, _bz2,
> _locale, audioop, _ctypes_test, _weakref, _locale)
> * Marcel Plch (PEP 573)
> * Martin von Löwis (PEP 3121)
> * Mohamed Koubaa (modules: sha256, multiprocessing, _winapi, _blake2,
> _sha3, _signal, _sha1, _sha512, _md5, zlib, _opcode, _overlapped,
> _curses_panel, termios, _sha256, scproxy, cmath, _lsprof, unicodedata)
> * Nick Coghlan (PEP 489, PEP 573)
> * Paulo Henrique Silva (modules: time, operator, _functools)
> * Petr Viktorin (PEP 489, PEP 573, PEP 630)
> * Stefan Behnel (PEP 489)
> * Victor Stinner (modules _string, mashal,_imp, _warnings, _thread)
>
> The work was scatted into many sub-issues, it was hard for me to track
> all persons who contributed, sorry about that! I only searched for
> "New changeset" in bpo-1635741.
>
> For me, it was a very pleasant collaborative work :-) Contributors
> wrote pull requests, I reviewed and merged them. Slowly, contributors
> started to review each others and shared some recipes for these tasks.
>
>
> == Close the very old bpo-1635741 issue ==
>
> Today, in the main development branch, Python no longer leaks memory
> at
