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gh-94673: Clarify About Runtime State Related to Static Builtin Types #117761

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Merged
ericsnowcurrently merged 8 commits into from
Apr 12, 2024
Merged

gh-94673: Clarify About Runtime State Related to Static Builtin Types #117761

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c0b035e
Add a note about the static builtin types to struct types_state.
ericsnowcurrently Apr 11, 2024
a73483b
Add asserts for static builtin type initialization constraints.
ericsnowcurrently Apr 11, 2024
b8d622e
Add _PyRuntimeState.types.next_builtin_index.
ericsnowcurrently Apr 11, 2024
00feed6
Revert "Add _PyRuntimeState.types.next_builtin_index."
ericsnowcurrently Apr 12, 2024
6e1853b
Describe the correct type for tp_subclasses.
ericsnowcurrently Apr 12, 2024
7b029d9
Clarify that tp_subclasses is PyObject* for other type objects.
ericsnowcurrently Apr 12, 2024
7cf7c04
Flip around the condition in static_builtin_state_init().
ericsnowcurrently Apr 12, 2024
f668cf1
Drop an unnecessary line escape.
ericsnowcurrently Apr 12, 2024
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Add a note about the static builtin types to struct types_state.
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@ericsnowcurrently
ericsnowcurrently committed Apr 11, 2024
commit c0b035e86ac4d9ac23c4fc4b23d450b5ee28e8df
34 changes: 34 additions & 0 deletions Include/internal/pycore_typeobject.h
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Expand Up @@ -68,6 +68,40 @@ struct types_state {
unsigned int next_version_tag;

struct type_cache type_cache;

/* Every static builtin type is initialized for each interpreter
during its own initialization, including for the main interpreter
during global runtime initialization. This is done by calling
_PyStaticType_InitBuiltin().

The first time a static builtin type is initialized, all the
normal PyType_Ready() stuff happens. The only difference from
normal is that there are three PyTypeObject fields holding
objects which are stored here (on PyInterpreterState) rather
than in the corresponding PyTypeObject fields. Those are:
tp_dict (cls.__dict__), tp_subclasses (cls.__subclasses__),
and tp_weaklist.

When a subinterpreter is initialized, each static builtin type
is still initialized, but only the interpreter-specific portion,
namely those three objects.

Those objects are stored in the PyInterpreterState.types.builtins
array, at the index corresponding to each specific static builtin
type. That index (a size_t value) is stored in the tp_subclasses
field (defined as PyObject*). We re-purposed the now-unused
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@gvanrossum gvanrossum Apr 12, 2024

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Actually, it's void *.

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@ericsnowcurrently ericsnowcurrently Apr 12, 2024

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fixed

tp_subclasses to avoid adding another field to PyTypeObject.

The index for each static builtin type isn't statically assigned.
Instead it is calculated the first time a type is initialized
(by the main interpreter). The index matches the order in which
the type was initialized relative to the others. The actual
value comes from the current value of num_builtins_initialized,
as each type is initialized for the main interpreter.

num_builtins_initialized is incremented once for each static
builtin type. Once initialization is over for a subinterpreter,
the value will be the same as for all other interpreters. */
size_t num_builtins_initialized;
static_builtin_state builtins[_Py_MAX_STATIC_BUILTIN_TYPES];
PyMutex mutex;
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