Merge pull request #3976 from ngoldbaum/free-threaded-random-fix

Do not warn about possibly unreferenced RNGs on free-threaded CPython

AUTHORS.rst

@@ -130,6 +130,7 @@ their individual contributions.
 * `Michel Alexandre Salim <https://github.com/michel-slm>`_ (michel@michel-slm.name)
 * `mulkieran <https://www.github.com/mulkieran>`_
 * `Munir Abdinur <https://www.github.com/mabdinur>`_
+* `Nathan Goldbaum <https://www/github.com/ngoldbaum>`_
 * `Nicholas Chammas <https://www.github.com/nchammas>`_
 * `Nick Anyos <https://www.github.com/NickAnyos>`_
 * `Nick Collins <https://github.com/nickcollins>` _

hypothesis-python/RELEASE.rst

@@ -0,0 +1,8 @@
+RELEASE_TYPE: patch
+
+This patch turns off a check in :func:`~hypothesis.register_random` for possibly
+unreferenced RNG instances on the free-threaded build of CPython 3.13 because
+this check has a much higher false positive rate in the free-threaded build
+(:issue:`3965`).
+
+Thanks to Nathan Goldbaum for this patch.

hypothesis-python/src/hypothesis/internal/compat.py

@@ -14,6 +14,7 @@
 import inspect
 import platform
 import sys
+import sysconfig
 import typing
 from functools import partial
 from typing import Any, ForwardRef, List, Optional, get_args
@@ -43,6 +44,8 @@
 PYPY = platform.python_implementation() == "PyPy"
 GRAALPY = platform.python_implementation() == "GraalVM"
 WINDOWS = platform.system() == "Windows"
+# First defined in CPython 3.13, defaults to False
+FREE_THREADED_CPYTHON = bool(sysconfig.get_config_var("Py_GIL_DISABLED"))
 
 
 def add_note(exc, note):

hypothesis-python/src/hypothesis/internal/entropy.py

@@ -19,7 +19,7 @@
 
 import hypothesis.core
 from hypothesis.errors import HypothesisWarning, InvalidArgument
-from hypothesis.internal.compat import GRAALPY, PYPY
+from hypothesis.internal.compat import FREE_THREADED_CPYTHON, GRAALPY, PYPY
 
 if TYPE_CHECKING:
     from typing import Protocol
@@ -116,7 +116,7 @@ def my_WORKING_hook():
         return
 
     if not (PYPY or GRAALPY):  # pragma: no branch
-        # PYPY and GRAALPY do not have `sys.getrefcount`
+        # PYPY and GRAALPY do not have `sys.getrefcount`.
         gc.collect()
         if not gc.get_referrers(r):
             if sys.getrefcount(r) <= _PLATFORM_REF_COUNT:
@@ -127,7 +127,12 @@ def my_WORKING_hook():
                     "PRNG. See the docs for `register_random` for more "
                     "details."
                 )
-            else:
+            elif not FREE_THREADED_CPYTHON:
+                # On CPython, check for the free-threaded build because
+                # gc.get_referrers() ignores objects with immortal refcounts
+                # and objects are immortalized in the Python 3.13
+                # free-threading implementation at runtime.
+
                 warnings.warn(
                     "It looks like `register_random` was passed an object that could "
                     "be garbage collected immediately after `register_random` creates "