Make `warnings.catch_warnings()` use a context variable for holding
the warning filtering state if the `sys.flags.context_aware_warnings`
flag is set to true. This makes using the context manager thread-safe in
multi-threaded programs.
Add the `sys.flags.thread_inherit_context` flag. If true, starting a new
thread with `threading.Thread` will use a copy of the context
from the caller of `Thread.start()`.
Both these flags are set to true by default for the free-threaded build
and false for the default build.
Move the Python implementation of warnings.py into _py_warnings.py.
Make _contextvars a builtin module.
Co-authored-by: Kumar Aditya <kumaraditya@python.org>
* Add `_PyDictKeys_StringLookupSplit` which does locking on dict keys and
use in place of `_PyDictKeys_StringLookup`.
* Change `_PyObject_TryGetInstanceAttribute` to use that function
in the case of split keys.
* Add `unicodekeys_lookup_split` helper which allows code sharing
between `_Py_dict_lookup` and `_PyDictKeys_StringLookupSplit`.
* Fix locking for `STORE_ATTR_INSTANCE_VALUE`. Create
`_GUARD_TYPE_VERSION_AND_LOCK` uop so that object stays locked and
`tp_version_tag` cannot change.
* Pass `tp_version_tag` to `specialize_dict_access()`, ensuring
the version we store on the cache is the correct one (in case of
it changing during the specalize analysis).
* Split `analyze_descriptor` into `analyze_descriptor_load` and
`analyze_descriptor_store` since those don't share much logic.
Add `descriptor_is_class` helper function.
* In `specialize_dict_access`, double check `_PyObject_GetManagedDict()`
in case we race and dict was materialized before the lock.
* Avoid borrowed references in `_Py_Specialize_StoreAttr()`.
* Use `specialize()` and `unspecialize()` helpers.
* Add unit tests to ensure specializing happens as expected in FT builds.
* Add unit tests to attempt to trigger data races (useful for running under TSAN).
* Add `has_split_table` function to `_testinternalcapi`.
* Replace uses of `PyCell_GET` and `PyCell_SET`. These macros are not
safe to use in the free-threaded build. Use `PyCell_GetRef()` and
`PyCell_SetTakeRef()` instead.
* Since `PyCell_GetRef()` returns a strong rather than borrowed ref, some
code restructuring was required, e.g. `frame_get_var()` returns a strong
ref now.
* Add critical sections to `PyCell_GET` and `PyCell_SET`.
* Move critical_section.h earlier in the Python.h file.
* Add `PyCell_GET` to the free-threading howto table of APIs that return
borrowed refs.
* Add additional unit tests for free-threading.
Neil Schemenauer