Sep 14, 2021 · Sep 5, 2021
diff --git a/src/embed_tests/Inheritance.cs b/src/embed_tests/Inheritance.cs
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Runtime.InteropServices;

 using NUnit.Framework;

            int actual = scope.Eval<int>($"{nameof(instance)}.{nameof(Inherited.XProp)}");
            Assert.AreEqual(expected: Inherited.X, actual);
        }

        // https://github.com/pythonnet/pythonnet/issues/1476
        [Test]
        public void BaseClearIsCalled()
        {
            using var scope = Py.CreateScope();
            scope.Set("exn", new Exception("42"));
            var msg = scope.Eval("exn.args[0]");
            Assert.AreEqual(2, msg.Refcount);
            scope.Set("exn", null);
            Assert.AreEqual(1, msg.Refcount);
        }
    }

    class ExtraBaseTypeProvider : IPythonBaseTypeProvider
diff --git a/src/runtime/classbase.cs b/src/runtime/classbase.cs
 using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Runtime.InteropServices;

 namespace Python.Runtime
 {
            if (!isTypeObject)
            {
                ClearObjectDict(ob);

                int baseClearResult = BaseUnmanagedClear(ob);
                if (baseClearResult != 0)
                {
                    return baseClearResult;
                }
            }
            if (self is not null) self.tpHandle = IntPtr.Zero;
            return 0;
        }

        static unsafe int BaseUnmanagedClear(IntPtr ob)
        {
            var type = Runtime.PyObject_TYPE(new BorrowedReference(ob));
            var unmanagedBase = GetUnmanagedBaseType(type);
            var clearPtr = Marshal.ReadIntPtr(unmanagedBase.DangerousGetAddress(), TypeOffset.tp_clear);
            if (clearPtr == IntPtr.Zero)
            {
                return 0;
            }
            var clear = (delegate* unmanaged[Cdecl]<IntPtr, int>)clearPtr;
            return clear(ob);
        }

        protected override void OnSave(InterDomainContext context)
        {
            base.OnSave(context);
diff --git a/src/runtime/managedtype.cs b/src/runtime/managedtype.cs
            return (flags & TypeFlags.HasClrInstance) != 0;
        }

        internal static BorrowedReference GetUnmanagedBaseType(BorrowedReference managedType)
        {
            Debug.Assert(managedType != null && IsManagedType(managedType));
            do
            {
                managedType = PyType.GetBase(managedType);
            } while (IsManagedType(managedType));
            return managedType;
        }

        public bool IsClrMetaTypeInstance()
        {
            Debug.Assert(Runtime.PyCLRMetaType != IntPtr.Zero);
diff --git a/src/runtime/pytype.cs b/src/runtime/pytype.cs
 #nullable enable
 using System;
 using System.Diagnostics;
 using System.Runtime.InteropServices;

 using Python.Runtime.Native;

            return Runtime.PyType_Check(value.obj);
        }
        /// <summary>Checks if specified object is a Python type.</summary>
        internal static bool IsType(BorrowedReference value)
        {
            return Runtime.PyType_Check(value.DangerousGetAddress());
        }

        /// <summary>
        /// Gets <see cref="PyType"/>, which represents the specified CLR type.

        internal BorrowedReference BaseReference
        {
            get
            {
                return new(Marshal.ReadIntPtr(Handle, TypeOffset.tp_base));
            }
            get => GetBase(Reference);
            set
            {
                var old = BaseReference.DangerousGetAddressOrNull();
            return Exceptions.ErrorCheckIfNull(result);
        }

        internal static BorrowedReference GetBase(BorrowedReference type)
        {
            Debug.Assert(IsType(type));
            IntPtr basePtr = Marshal.ReadIntPtr(type.DangerousGetAddress(), TypeOffset.tp_base);
            return new BorrowedReference(basePtr);
        }

        private static IntPtr EnsureIsType(in StolenReference reference)
        {
            IntPtr address = reference.DangerousGetAddressOrNull();
Original file line number	Diff line number	Diff line change
		@@ -1,7 +1,5 @@
		using System;
		using System.Collections.Generic;
		using System.Diagnostics;
		using System.Runtime.InteropServices;

		using NUnit.Framework;

Expand DownExpand Up		@@ -100,6 +98,18 @@ public void SetAdHocAttributes_WhenExtraBasePresent()
		int actual = scope.Eval<int>($"{nameof(instance)}.{nameof(Inherited.XProp)}");
		Assert.AreEqual(expected: Inherited.X, actual);
		}

		// https://github.com/pythonnet/pythonnet/issues/1476
		[Test]
		public void BaseClearIsCalled()
		{
		using var scope = Py.CreateScope();
		scope.Set("exn", new Exception("42"));
		var msg = scope.Eval("exn.args[0]");
		Assert.AreEqual(2, msg.Refcount);
		scope.Set("exn", null);
		Assert.AreEqual(1, msg.Refcount);
		}
		}

		class ExtraBaseTypeProvider : IPythonBaseTypeProvider
Expand Down
Original file line number	Diff line number	Diff line change
		@@ -1,6 +1,7 @@
		using System;
		using System.Collections;
		using System.Collections.Generic;
		using System.Runtime.InteropServices;

		namespace Python.Runtime
		{
Expand DownExpand Up		@@ -365,11 +366,30 @@ public static int tp_clear(IntPtr ob)
		if (!isTypeObject)
		{
		ClearObjectDict(ob);

		int baseClearResult = BaseUnmanagedClear(ob);
		if (baseClearResult != 0)
		{
		return baseClearResult;
		}
		}
		if (self is not null) self.tpHandle = IntPtr.Zero;
		return 0;
		}

		static unsafe int BaseUnmanagedClear(IntPtr ob)
		{
		var type = Runtime.PyObject_TYPE(new BorrowedReference(ob));
		var unmanagedBase = GetUnmanagedBaseType(type);
		var clearPtr = Marshal.ReadIntPtr(unmanagedBase.DangerousGetAddress(), TypeOffset.tp_clear);
		if (clearPtr == IntPtr.Zero)
		{
		return 0;
		}
		var clear = (delegate* unmanaged[Cdecl]<IntPtr, int>)clearPtr;
		return clear(ob);
		}

		protected override void OnSave(InterDomainContext context)
		{
		base.OnSave(context);
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -149,6 +149,16 @@ internal static bool IsManagedType(BorrowedReference type)
		return (flags & TypeFlags.HasClrInstance) != 0;
		}

		internal static BorrowedReference GetUnmanagedBaseType(BorrowedReference managedType)
		{
		Debug.Assert(managedType != null && IsManagedType(managedType));
		do
		{
		managedType = PyType.GetBase(managedType);
		} while (IsManagedType(managedType));
		return managedType;
		}

		public bool IsClrMetaTypeInstance()
		{
		Debug.Assert(Runtime.PyCLRMetaType != IntPtr.Zero);
Expand Down
Original file line number	Diff line number	Diff line change
		@@ -1,5 +1,6 @@
		#nullable enable
		using System;
		using System.Diagnostics;
		using System.Runtime.InteropServices;

		using Python.Runtime.Native;
Expand DownExpand Up		@@ -60,6 +61,11 @@ public static bool IsType(PyObject value)

		return Runtime.PyType_Check(value.obj);
		}
		/// <summary>Checks if specified object is a Python type.</summary>
		internal static bool IsType(BorrowedReference value)
		{
		return Runtime.PyType_Check(value.DangerousGetAddress());
		}

		/// <summary>
		/// Gets <see cref="PyType"/>, which represents the specified CLR type.
Expand All		@@ -78,10 +84,7 @@ internal static PyType Get(Type clrType)

		internal BorrowedReference BaseReference
		{
		get
		{
		return new(Marshal.ReadIntPtr(Handle, TypeOffset.tp_base));
		}
		get => GetBase(Reference);
		set
		{
		var old = BaseReference.DangerousGetAddressOrNull();
Expand All		@@ -100,6 +103,13 @@ internal IntPtr GetSlot(TypeSlotID slot)
		return Exceptions.ErrorCheckIfNull(result);
		}

		internal static BorrowedReference GetBase(BorrowedReference type)
		{
		Debug.Assert(IsType(type));
		IntPtr basePtr = Marshal.ReadIntPtr(type.DangerousGetAddress(), TypeOffset.tp_base);
		return new BorrowedReference(basePtr);
		}

		private static IntPtr EnsureIsType(in StolenReference reference)
		{
		IntPtr address = reference.DangerousGetAddressOrNull();
Expand Down