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gh-117953: Other Cleanups in the Extensions Machinery (gh-118206)
This change will make some later changes simpler.
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‎Lib/test/test_import/__init__.py

Lines changed: 109 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -2285,6 +2285,107 @@ def test_disallowed_reimport(self):
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class TestSinglePhaseSnapshot(ModuleSnapshot):
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"""A representation of a single-phase init module for testing.
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Fields from ModuleSnapshot:
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* id - id(mod)
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* module - mod or a SimpleNamespace with __file__ & __spec__
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* ns - a shallow copy of mod.__dict__
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* ns_id - id(mod.__dict__)
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* cached - sys.modules[name] (or None if not there or not snapshotable)
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* cached_id - id(sys.modules[name]) (or None if not there)
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Extra fields:
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* summed - the result of calling "mod.sum(1, 2)"
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* lookedup - the result of calling "mod.look_up_self()"
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* lookedup_id - the object ID of self.lookedup
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* state_initialized - the result of calling "mod.state_initialized()"
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* init_count - (optional) the result of calling "mod.initialized_count()"
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Overridden methods from ModuleSnapshot:
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* from_module()
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* parse()
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Other methods from ModuleSnapshot:
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* build_script()
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* from_subinterp()
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----
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There are 5 modules in Modules/_testsinglephase.c:
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* _testsinglephase
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* has global state
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* extra loads skip the init function, copy def.m_base.m_copy
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* counts calls to init function
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* _testsinglephase_basic_wrapper
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* _testsinglephase by another name (and separate init function symbol)
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* _testsinglephase_basic_copy
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* same as _testsinglephase but with own def (and init func)
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* _testsinglephase_with_reinit
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* has no global or module state
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* mod.state_initialized returns None
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* an extra load in the main interpreter calls the cached init func
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* an extra load in legacy subinterpreters does a full load
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* _testsinglephase_with_state
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* has module state
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* an extra load in the main interpreter calls the cached init func
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* an extra load in legacy subinterpreters does a full load
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(See Modules/_testsinglephase.c for more info.)
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For all those modules, the snapshot after the initial load (not in
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the global extensions cache) would look like the following:
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* initial load
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* id: ID of nww module object
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* ns: exactly what the module init put there
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* ns_id: ID of new module's __dict__
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* cached_id: same as self.id
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* summed: 3 (never changes)
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* lookedup_id: same as self.id
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* state_initialized: a timestamp between the time of the load
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and the time of the snapshot
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* init_count: 1 (None for _testsinglephase_with_reinit)
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For the other scenarios it varies.
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For the _testsinglephase, _testsinglephase_basic_wrapper, and
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_testsinglephase_basic_copy modules, the snapshot should look
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like the following:
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* reloaded
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* id: no change
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* ns: matches what the module init function put there,
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including the IDs of all contained objects,
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plus any extra attributes added before the reload
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* ns_id: no change
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* cached_id: no change
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* lookedup_id: no change
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* state_initialized: no change
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* init_count: no change
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* already loaded
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* (same as initial load except for ns and state_initialized)
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* ns: matches the initial load, incl. IDs of contained objects
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* state_initialized: no change from initial load
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For _testsinglephase_with_reinit:
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* reloaded: same as initial load (old module & ns is discarded)
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* already loaded: same as initial load (old module & ns is discarded)
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For _testsinglephase_with_state:
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* reloaded
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* (same as initial load (old module & ns is discarded),
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except init_count)
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* init_count: increase by 1
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* already loaded: same as reloaded
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"""
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@classmethod
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def from_module(cls, mod):
@@ -2901,17 +3002,18 @@ def test_basic_multiple_interpreters_deleted_no_reset(self):
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# * module's global state was initialized but cleared
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# Start with an interpreter that gets destroyed right away.
2904-
base = self.import_in_subinterp(postscript='''
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# Attrs set after loading are not in m_copy.
2906-
mod.spam = 'spam, spam, mash, spam, eggs, and spam'
2907-
''')
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base = self.import_in_subinterp(
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postscript='''
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# Attrs set after loading are not in m_copy.
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mod.spam = 'spam, spam, mash, spam, eggs, and spam'
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''')
29083010
self.check_common(base)
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self.check_fresh(base)
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29113013
# At this point:
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# * alive in 0 interpreters
29133015
# * module def in _PyRuntime.imports.extensions
2914-
# * mod init func ran again
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# * mod init func ran for the first time (since reset)
29153017
# * m_copy is NULL (claered when the interpreter was destroyed)
29163018
# * module's global state was initialized, not reset
29173019

@@ -2923,7 +3025,7 @@ def test_basic_multiple_interpreters_deleted_no_reset(self):
29233025
# At this point:
29243026
# * alive in 1 interpreter (interp1)
29253027
# * module def still in _PyRuntime.imports.extensions
2926-
# * mod init func ran again
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# * mod init func ran for the second time (since reset)
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# * m_copy was copied from interp1 (was NULL)
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# * module's global state was updated, not reset
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@@ -2935,7 +3037,7 @@ def test_basic_multiple_interpreters_deleted_no_reset(self):
29353037
# At this point:
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# * alive in 2 interpreters (interp1, interp2)
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# * module def still in _PyRuntime.imports.extensions
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# * mod init func ran again
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# * mod init func did not run again
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# * m_copy was copied from interp2 (was from interp1)
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# * module's global state was updated, not reset
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‎Modules/_testsinglephase.c

Lines changed: 167 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,172 @@
11

22
/* Testing module for single-phase initialization of extension modules
3-
*/
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This file contains 5 distinct modules, meaning each as its own name
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and its own init function (PyInit_...). The default import system will
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only find the one matching the filename: _testsinglephase. To load the
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others you must do so manually. For example:
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```python
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name = '_testsinglephase_base_wrapper'
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filename = _testsinglephase.__file__
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loader = importlib.machinery.ExtensionFileLoader(name, filename)
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spec = importlib.util.spec_from_file_location(name, filename, loader=loader)
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mod = importlib._bootstrap._load(spec)
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```
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Here are the 5 modules:
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* _testsinglephase
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* def: _testsinglephase_basic,
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* m_name: "_testsinglephase"
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* m_size: -1
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* state
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* process-global
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* <int> initialized_count (default to -1; will never be 0)
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* <module_state> module (see module state below)
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* module state: no
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* initial __dict__: see common initial __dict__ below
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* init function
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1. create module
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2. clear <global>.module
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3. initialize <global>.module: see module state below
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4. initialize module: set initial __dict__
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5. increment <global>.initialized_count
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* functions
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* (3 common, see below)
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* initialized_count() - return <global>.module.initialized_count
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* import system
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* caches
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* global extensions cache: yes
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* def.m_base.m_copy: yes
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* def.m_base.m_init: no
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* per-interpreter cache: yes (all single-phase init modules)
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* load in main interpreter
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* initial (not already in global cache)
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1. get init function from shared object file
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2. run init function
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3. copy __dict__ into def.m_base.m_copy
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4. set entry in global cache
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5. set entry in per-interpreter cache
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6. set entry in sys.modules
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* reload (already in sys.modules)
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1. get def from global cache
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2. get module from sys.modules
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3. update module with contents of def.m_base.m_copy
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* already loaded in other interpreter (already in global cache)
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* same as reload, but create new module and update *it*
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* not in any sys.modules, still in global cache
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* same as already loaded
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* load in legacy (non-isolated) interpreter
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* same as main interpreter
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* unload: never (all single-phase init modules)
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* _testsinglephase_basic_wrapper
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* identical to _testsinglephase except module name
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* _testsinglephase_basic_copy
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* def: static local variable in init function
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* m_name: "_testsinglephase_basic_copy"
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* m_size: -1
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* state: same as _testsinglephase
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* init function: same as _testsinglephase
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* functions: same as _testsinglephase
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* import system: same as _testsinglephase
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* _testsinglephase_with_reinit
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* def: _testsinglephase_with_reinit,
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* m_name: "_testsinglephase_with_reinit"
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* m_size: 0
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* state
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* process-global state: no
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* module state: no
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* initial __dict__: see common initial __dict__ below
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* init function
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1. create module
83+
2. initialize temporary module state (local var): see module state below
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3. initialize module: set initial __dict__
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* functions: see common functions below
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* import system
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* caches
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* global extensions cache: only if loaded in main interpreter
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* def.m_base.m_copy: no
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* def.m_base.m_init: only if loaded in the main interpreter
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* per-interpreter cache: yes (all single-phase init modules)
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* load in main interpreter
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* initial (not already in global cache)
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* (same as _testsinglephase except step 3)
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1. get init function from shared object file
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2. run init function
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3. set def.m_base.m_init to the init function
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4. set entry in global cache
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5. set entry in per-interpreter cache
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6. set entry in sys.modules
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* reload (already in sys.modules)
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1. get def from global cache
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2. call def->m_base.m_init to get a new module object
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3. replace the existing module in sys.modules
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* already loaded in other interpreter (already in global cache)
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* same as reload (since will only be in cache for main interp)
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* not in any sys.modules, still in global cache
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* same as already loaded
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* load in legacy (non-isolated) interpreter
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* initial (not already in global cache)
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* (same as main interpreter except skip steps 3 & 4 there)
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1. get init function from shared object file
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2. run init function
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...
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5. set entry in per-interpreter cache
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6. set entry in sys.modules
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* reload (already in sys.modules)
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* same as initial (load from scratch)
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* already loaded in other interpreter (already in global cache)
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* same as initial (load from scratch)
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* not in any sys.modules, still in global cache
122+
* same as initial (load from scratch)
123+
* unload: never (all single-phase init modules)
124+
* _testsinglephase_with_state
125+
* def: _testsinglephase_with_state,
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* m_name: "_testsinglephase_with_state"
127+
* m_size: sizeof(module_state)
128+
* state
129+
* process-global: no
130+
* module state: see module state below
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* initial __dict__: see common initial __dict__ below
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* init function
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1. create module
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3. initialize module state: see module state below
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4. initialize module: set initial __dict__
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5. increment <global>.initialized_count
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* functions: see common functions below
138+
* import system: same as _testsinglephase_basic_copy
139+
140+
Module state:
141+
142+
* fields
143+
* <PyTime_t> initialized - when the module was first initialized
144+
* <PyObject> *error
145+
* <PyObject> *int_const
146+
* <PyObject> *str_const
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* initialization
148+
1. set state.initialized to the current time
149+
2. set state.error to a new exception class
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3. set state->int_const to int(1969)
151+
4. set state->str_const to "something different"
152+
153+
Common initial __dict__:
154+
155+
* error: state.error
156+
* int_const: state.int_const
157+
* str_const: state.str_const
158+
* _module_initialized: state.initialized
159+
160+
Common functions:
161+
162+
* look_up_self() - return the module from the per-interpreter "by-index" cache
163+
* sum() - return a + b
164+
* state_initialized() - return state->initialized (or None if m_size == 0)
165+
166+
See Python/import.c, especially the long comments, for more about
167+
single-phase init modules.
168+
*/
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4170
#ifndef Py_BUILD_CORE_BUILTIN
5171
# define Py_BUILD_CORE_MODULE 1
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#endif

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