pythonnet · BadSingleton · Feb 11, 2021 · Feb 26, 2021 · Mar 4, 2021 · Mar 5, 2021
diff --git a/src/domain_tests/test_domain_reload.py b/src/domain_tests/test_domain_reload.py
@@ -56,7 +56,6 @@ def test_property_visibility_change():
 def test_class_visibility_change():
     _run_test("class_visibility_change")
 
-@pytest.mark.skip(reason='FIXME: Domain reload fails when Python points to a .NET object which points back to Python objects')
 def test_method_parameters_change():
     _run_test("method_parameters_change")
 

diff --git a/src/runtime/classbase.cs b/src/runtime/classbase.cs
@@ -517,5 +517,11 @@ public static int mp_ass_subscript(IntPtr ob, IntPtr idx, IntPtr v)
 
             return 0;
         }
+
+        public override string ToString()
+        {
+            return $"<ClassBase of {type}>";
+        }
+
     }
 }
diff --git a/src/runtime/clrobject.cs b/src/runtime/clrobject.cs
@@ -103,5 +103,10 @@ protected override void OnLoad(InterDomainContext context)
             GCHandle gc = AllocGCHandle(TrackTypes.Wrapper);
             Marshal.WriteIntPtr(pyHandle, ObjectOffset.magic(tpHandle), (IntPtr)gc);
         }
+
+        public override string ToString()
+        {
+            return $"<CLRObject: {inst}>";
+        }
     }
 }
diff --git a/src/runtime/exceptions.cs b/src/runtime/exceptions.cs
@@ -85,6 +85,26 @@ internal static Exception ToException(IntPtr ob)
             }
             return Runtime.PyUnicode_FromString(message);
         }
+
+        static void ClearOffsetHelper(IntPtr ob, int offset)
+        {
+            var field = Marshal.ReadIntPtr(ob, offset);
+            Runtime.XDecref(field);
+            Marshal.WriteIntPtr(ob, offset, IntPtr.Zero);
+        }
+
+        // As seen in exceptions.c, every derived type must also clean the base.
+        // TODO: once the call tp_traverse and tp_clear on the instance and not
+        // the type, implement those.
+        public new static void tp_dealloc(IntPtr self)
+        {
+            ClearOffsetHelper(self, ExceptionOffset.dict);
+            ClearOffsetHelper(self, ExceptionOffset.args);
+            ClearOffsetHelper(self, ExceptionOffset.traceback);
+            ClearOffsetHelper(self, ExceptionOffset.context);
+            ClearOffsetHelper(self, ExceptionOffset.cause);
+            ClassBase.tp_dealloc(self);
+        }
     }
 
     /// <summary>
@@ -183,7 +203,7 @@ internal static void SetArgsAndCause(IntPtr ob)
             {
                 // Note: For an AggregateException, InnerException is only the first of the InnerExceptions.
                 IntPtr cause = CLRObject.GetInstHandle(e.InnerException);
-                Marshal.WriteIntPtr(ob, ExceptionOffset.cause, cause);
+                Runtime.PyException_SetCause(ob, cause);
             }
         }
 
@@ -279,10 +299,7 @@ public static void SetError(Exception e)
             var pe = e as PythonException;
             if (pe != null)
             {
-                Runtime.XIncref(pe.PyType);
-                Runtime.XIncref(pe.PyValue);
-                Runtime.XIncref(pe.PyTB);
-                Runtime.PyErr_Restore(pe.PyType, pe.PyValue, pe.PyTB);
+                pe.Restore();
                 return;
             }
 
@@ -399,6 +416,7 @@ internal static IntPtr RaiseTypeError(string message)
             if (previousException != null)
             {
                 SetCause(previousException);
+                previousException.Dispose();
             }
             return IntPtr.Zero;
         }

diff --git a/src/runtime/importhook.cs b/src/runtime/importhook.cs
@@ -368,6 +368,7 @@ public static IntPtr __import__(IntPtr self, IntPtr argsRaw, IntPtr kw)
                 }
 
                 Runtime.XIncref(mod.pyHandle);
+                originalException.Dispose();
                 return mod.pyHandle;
             }
         }

diff --git a/src/testing/exceptiontest.cs b/src/testing/exceptiontest.cs
@@ -1,3 +1,4 @@
+using Python.Runtime;
 using System;
 using System.Collections;
 using System.Collections.Generic;
@@ -81,6 +82,38 @@ public static void ThrowChainedExceptions()
                 throw new Exception("Outer exception", exc2);
             }
         }
+        public static IntPtr DoThrowSimple()
+        {
+            using (Py.GIL())
+            {
+                // Set a python TypeError.
+                Exceptions.SetError(Exceptions.TypeError, "type error, The first.");
+                var pyerr = new PythonException();
+                // PyErr_Fetch() it and set it as the cause of an ArgumentException (and raise).
+                throw new ArgumentException("Bogus bad parameter", pyerr);
+            }
+        }
+
+        public static void DoThrowWithInner()
+        {
+            using(Py.GIL())
+            {
+                // Set a python TypeError.
+                Exceptions.SetError(Exceptions.TypeError, "type error, The first.");
+                var pyerr = new PythonException();
+                // PyErr_Fetch() it and set it as the cause of an ArgumentException (and raise).
+                Exceptions.SetError(new ArgumentException("Bogus bad parameter", pyerr));
+                // But we want Python error.. raise a TypeError and set the cause to the 
+                // previous ArgumentError.
+                PythonException previousException = new PythonException();
+                Exceptions.SetError(Exceptions.TypeError, "type error, The second.");
+                Exceptions.SetCause(previousException);
+                previousException.Dispose();
+                // Then throw-raise the TypeError.
+                throw new PythonException();
+            }
+        }
+
     }
 
 

diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
@@ -9,6 +9,53 @@
 import pickle
 
 
+# begin code from https://utcc.utoronto.ca/~cks/space/blog/python/GetAllObjects
+import gc
+# Recursively expand slist's objects
+# into olist, using seen to track
+# already processed objects.
+
+def _getr(slist, olist, seen):
+    for e in slist:
+      if id(e) in seen:
+        continue
+      seen[id(e)] = None
+      olist.append(e)
+      tl = gc.get_referents(e)
+      if tl:
+        _getr(tl, olist, seen)
+
+# The public function.
+def get_all_objects():
+    gcl = gc.get_objects()
+    olist = []
+    seen = {}
+    # Just in case:
+    seen[id(gcl)] = None
+    seen[id(olist)] = None
+    seen[id(seen)] = None
+    # _getr does the real work.
+    _getr(gcl, olist, seen)
+    return olist
+# end code from https://utcc.utoronto.ca/~cks/space/blog/python/GetAllObjects
+
+def leak_check(func):
+    def do_leak_check():
+        func()
+        gc.collect()
+        exc = {x for x in get_all_objects() if isinstance(x, Exception) and not isinstance(x, pytest.PytestDeprecationWarning)}
+        print(len(exc))
+        if len(exc):
+            for x in exc:
+                print('-------')
+                print(repr(x))
+                print(gc.get_referrers(x))
+                print(len(gc.get_referrers(x)))
+            assert False
+    gc.collect()
+    return do_leak_check
+
+
 def test_unified_exception_semantics():
     """Test unified exception semantics."""
     e = System.Exception('Something bad happened')
@@ -375,3 +422,31 @@ def test_iteration_innerexception():
     # after exception is thrown iterator is no longer valid
     with pytest.raises(StopIteration):
         next(val)
+
+def leak_test(func):
+    def do_test_leak():
+        # PyTest leaks things, gather the current state
+        orig_exc = {x for x in get_all_objects() if isinstance(x, Exception)}
+        func()
+        exc = {x for x in get_all_objects() if isinstance(x, Exception)}
+        possibly_leaked = exc - orig_exc
+        assert not possibly_leaked
+
+    return do_test_leak
+
+@leak_test
+def test_dont_leak_exceptions_simple():
+    from Python.Test import ExceptionTest
+
+    try:
+        ExceptionTest.DoThrowSimple()
+    except System.ArgumentException:
+        print('type error, as expected')
+
+@leak_test
+def test_dont_leak_exceptions_inner():
+    from Python.Test import ExceptionTest
+    try:
+        ExceptionTest.DoThrowWithInner()
+    except TypeError:
+        print('type error, as expected')
-Original file line number
+Diff line change
@@ Expand Up @@
                     }
                     Runtime.XIncref(mod.pyHandle);
+                    originalException.Dispose();
                     return mod.pyHandle;
                 }
             }
@@ Expand Down @@