avoid copying code objects for ki protected function

Author: graingert

src/trio/_core/_ki.py

@@ -226,9 +226,7 @@ def enable_ki_protection(f: _T_supports_code, /) -> _T_supports_code:
     if legacy_isasyncgenfunction(f):
         f = f.__wrapped__  # type: ignore
 
-    code = f.__code__.replace()
-    _CODE_KI_PROTECTION_STATUS_WMAP[code] = True
-    f.__code__ = code
+    _CODE_KI_PROTECTION_STATUS_WMAP[f.__code__] = True
     return orig
 
 
@@ -239,9 +237,7 @@ def disable_ki_protection(f: _T_supports_code, /) -> _T_supports_code:
     if legacy_isasyncgenfunction(f):
         f = f.__wrapped__  # type: ignore
 
-    code = f.__code__.replace()
-    _CODE_KI_PROTECTION_STATUS_WMAP[code] = False
-    f.__code__ = code
+    _CODE_KI_PROTECTION_STATUS_WMAP[f.__code__] = False
     return orig
 
 

src/trio/_core/_tests/test_ki.py

@@ -529,6 +529,14 @@ def _identity(v: _T) -> _T:
     return v
 
 
+@pytest.mark.xfail(
+    strict=True,
+    raises=AssertionError,
+    reason=(
+        "it was decided not to protect against this case, see discussion in: "
+        "https://github.com/python-trio/trio/pull/3110#discussion_r1802123644"
+    ),
+)
 async def test_ki_does_not_leak_accross_different_calls_to_inner_functions() -> None:
     assert not _core.currently_ki_protected()