GH-115776: Embed the values array into the object, for "normal" Python objects. #116115

markshannon · 2024-02-29T11:43:12Z

A "normal" Python object is one that:

Doesn't inherit from a builtin class
Does not have __slots__

Issue: Inline values array into the object #115776

… of object.

DinoV

Looks awesome, just a few nits!

Objects/dictobject.c

Include/internal/pycore_object.h

Objects/dictobject.c

scoder · 2024-04-09T09:04:12Z

Include/internal/pycore_object.h

-    if (_PyType_HasFeature(typeobj, Py_TPFLAGS_HEAPTYPE)) {
-        Py_INCREF(typeobj);
-    }
+    assert(_PyType_HasFeature(typeobj, Py_TPFLAGS_HEAPTYPE) || _Py_IsImmortal(typeobj));


I now hit this assertion in Cython modules. The (static) extension type that we use for generators has tp_alloc = PyType_GenericAlloc and calls it in tp_new():

#6 0x00007ffff7cc2e96 in __GI___assert_fail (assertion=assertion@entry=0x5555559db4e0 "_PyType_HasFeature(typeobj, Py_TPFLAGS_HEAPTYPE) || _Py_IsImmortal(typeobj)", file=file@entry=0x5555559db468 "./Include/internal/pycore_object.h", line=line@entry=268, function=function@entry=0x555555a04ad8 <__PRETTY_FUNCTION__.140> "_PyObject_Init") at ./assert/assert.c:101 #7 0x0000555555774e33 in _PyObject_Init (typeobj=0x7ffff6c26d40 <__pyx_type_8buildenv___pyx_scope_struct__genexpr>, op=0x7ffff4f1e210) at ./Include/internal/pycore_object.h:268 #8 0x000055555577cec3 in _PyObject_Init (typeobj=<optimized out>, op=<optimized out>) at ./Include/object.h:430 #9 _PyType_AllocNoTrack (type=type@entry=0x7ffff6c26d40 <__pyx_type_8buildenv___pyx_scope_struct__genexpr>, nitems=0) at Objects/typeobject.c:1908 #10 0x000055555577cf09 in PyType_GenericAlloc (type=0x7ffff6c26d40 <__pyx_type_8buildenv___pyx_scope_struct__genexpr>, nitems=<optimized out>) at Objects/typeobject.c:1922 #11 0x00007ffff6c08100 in __pyx_tp_new_8buildenv___pyx_scope_struct__genexpr (t=<optimized out>, a=<optimized out>, k=k@entry=0x0) at buildenv.c:2954

Is this assertion simply wrong, or is there anything I can do to avoid it? The "immortal objects" API doesn't seem to be intended for public use.

#19474 sets the reference count to 1 for statically allocated objects unless Py_BUILD_CORE is defined.

As a workaround, I'd suggest making these classes immortal and making them immutable if you can.

The "immortal objects" API doesn't seem to be intended for public use.

That does seem to be the case. I don't know why. Want to open an issue for that?

Is there a reason why this new assertion exists? The previous if condition came from a conservative change that intended to avoid refcounting static types but wanted to make sure (heap) type objects are correctly kept alive as long as their objects. Now the code requires all non-heap types to be declared immortal. That seems a rather heavy change in requirements.

All non-heap types are immortal. Requiring that they are declared as such seems reasonable, and is probably necessary for memory safety.

I don't think you should need to do so explicitly though, PyObject_HEAD_INIT should do it.

Does #117673 fix the problem for you?

… Python objects. (pythonGH-116115)

python/cpython#116115 introduced a bug (python/cpython#125608) where changing the attributes of an object may not fire the dict watchers registered to the object's `__dict__`. It has been fixed by python/cpython#125611 but will only be in 3.13.1+. This PR disables the dict watcher guard shortcut for `__dict__`s on 3.13.0 and warns the user to try using 3.13.1+ instead. We also added a simple test to check for this functionality in the future. cc voznesenskym penguinwu EikanWang jgong5 Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng chauhang amjames rec [ghstack-poisoned]

python/cpython#116115 introduced a bug (python/cpython#125608) where changing the attributes of an object may not fire the dict watchers registered to the object's `__dict__`. It has been fixed by python/cpython#125611 but will only be in 3.13.1+. This PR disables the dict watcher guard shortcut for `__dict__`s on 3.13.0 and warns the user to try using 3.13.1+ instead. We also added a simple test to check for this functionality in the future. Pull Request resolved: #138284 Approved by: https://github.com/jansel ghstack dependencies: #138030

python/cpython#116115 introduced a bug (python/cpython#125608) where changing the attributes of an object may not fire the dict watchers registered to the object's `__dict__`. It has been fixed by python/cpython#125611 but will only be in 3.13.1+. This PR disables the dict watcher guard shortcut for `__dict__`s on 3.13.0 and warns the user to try using 3.13.1+ instead. We also added a simple test to check for this functionality in the future. Pull Request resolved: pytorch#138284 Approved by: https://github.com/jansel ghstack dependencies: pytorch#138030

markshannon added 28 commits February 3, 2024 23:56

Inline values work in progress

d5085db

Change layout of PyDictValue to make is suitable for appending to end…

0d88de4

… of object.

Add copy_values function

d922903

Tidy up _PyObject_Init

c03e6cb

Inline values -- Work in progress

621ea3b

Get inline values closer to working

67daab5

Further fixing

34c7171

Remove debug field

c237e79

Remove unused function

f80befa

Merge branch 'main' into inline-values

a0c11e4

Two tweaks

bc1ebc8

Rename dict-or-values to managed-dict

0dc68a4

Update object layout doc

084519c

Add news

3744f32

Fix a couple of compilation errors on Windows

75ee5a0

Update gdb support

162764c

Specialize LOAD_ATTR for (uninitialized) managed dicts

82ece1b

Allow extra allocation in JIT for tests.

6a762ed

Fix error from merge

9dbc8dd

Fix another mis-merge and update generated files

4a1f7b7

Fix formatting

09121f9

Fix up free threading

c384b05

Merge branch 'main' into inline-values

ee5cf2a

Remove incorrect assertion

005b42b

Merge branch 'main' into inline-values

48d849e

Remove some debug code

682217c

Fix off by one error.

0ff1709

Simplify PyObject_ClearManagedDict

895a944

markshannon requested review from gvanrossum and methane as code owners February 29, 2024 11:43

markshannon marked this pull request as ready for review March 26, 2024 17:14

bedevere-app bot added the awaiting core review label Mar 26, 2024

markshannon added 2 commits March 27, 2024 09:53

Review comment and compiler warnings

d441d7b

Update stats gathering.

3395bc2

DinoV approved these changes Mar 27, 2024

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bedevere-app bot added awaiting merge and removed awaiting core review labels Mar 27, 2024

markshannon added 2 commits March 28, 2024 11:18

Better type safety. Fewer downcasts, some more upcasts

ccceffb

Merge branch 'main' into inline-values

7700177

markshannon merged commit c32dc47 into python:main Apr 2, 2024
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bedevere-app bot removed the awaiting merge label Apr 2, 2024

scoder reviewed Apr 9, 2024

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markshannon mentioned this pull request Apr 9, 2024

GH-115776: Static object are immortal, so mark them as such. #117673

Merged

encukou mentioned this pull request Apr 11, 2024

_PyObject_StoreInstanceAttribute assertion fails in setattr after __dict__.clear() #117750

Closed

diegorusso pushed a commit to diegorusso/cpython that referenced this pull request Apr 17, 2024

pythonGH-115776: Embed the values array into the object, for "normal"…

735d3bf

… Python objects. (pythonGH-116115)

markshannon deleted the inline-values branch August 6, 2024 10:16

williamwen42 mentioned this pull request Oct 17, 2024

[dynamo] handle 3.13.0 __dict__ watcher bug pytorch/pytorch#138284

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GH-115776: Embed the values array into the object, for "normal" Python objects. #116115

GH-115776: Embed the values array into the object, for "normal" Python objects. #116115

markshannon commented Feb 29, 2024 •

edited by bedevere-app bot

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GH-115776: Embed the values array into the object, for "normal" Python objects. #116115

GH-115776: Embed the values array into the object, for "normal" Python objects. #116115

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markshannon commented Feb 29, 2024 •

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