Fixed the adjustment of the instance in cases of multiple inheritance.

Fixes https://github.com/mono/CppSharp/issues/707.

Signed-off-by: Dimitar Dobrev <dpldobrev@protonmail.com>

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -2513,7 +2513,12 @@ namespace CppSharp.Generators.CSharp
         private void GetVirtualCallDelegate(Method method, Class @class,
             out string delegateId)
         {
-            var i = VTables.GetVTableIndex(method.OriginalFunction ?? method, @class);
+            Function @virtual = method;
+            if (method.OriginalFunction != null &&
+                !((Class) method.OriginalFunction.Namespace).IsInterface)
+                @virtual = method.OriginalFunction;
+
+            var i = VTables.GetVTableIndex(@virtual, @class);
             int vtableIndex = 0;
             if (Context.ParserOptions.IsMicrosoftAbi)
                 vtableIndex = @class.Layout.VFTables.IndexOf(@class.Layout.VFTables.Where(
@@ -2526,7 +2531,7 @@ namespace CppSharp.Generators.CSharp
                 WriteStartBraceIndent();
             }
 
-            var @delegate = GetVTableMethodDelegateName(method.OriginalFunction ?? method);
+            var @delegate = GetVTableMethodDelegateName(@virtual);
             delegateId = Generator.GeneratedIdentifier(@delegate);
 
             WriteLine("var {0} = ({1}) Marshal.GetDelegateForFunctionPointer(new IntPtr({2}), typeof({1}));",
@@ -2823,11 +2828,14 @@ namespace CppSharp.Generators.CSharp
                 WriteCloseBraceIndent();
         }
 
-        private static string GetInstanceParam(Function function)
+        private string GetInstanceParam(Function function)
         {
             var from = (Class) function.Namespace;
-            var to = function.OriginalFunction == null ? @from.BaseClass :
-                (Class) function.OriginalFunction.Namespace;
+            var to = function.OriginalFunction == null ||
+                // we don't need to offset the instance with Itanium if there's an existing interface impl
+                (Context.ParserOptions.IsItaniumLikeAbi &&
+                 !((Class) function.OriginalNamespace).IsInterface) ?
+                @from.BaseClass : (Class) function.OriginalFunction.Namespace;
 
             var baseOffset = 0u;
             if (to != null)

src/Generator/Passes/MultipleInheritancePass.cs

@@ -160,15 +160,20 @@ namespace CppSharp.Passes
             return interfaceProperty;
         }
 
-        private static void ImplementInterfaceMethods(Class @class, Class @interface)
+        private void ImplementInterfaceMethods(Class @class, Class @interface)
         {
             foreach (var method in @interface.Methods)
             {
-                if (@class.Methods.Any(m => m.OriginalName == method.OriginalName &&
+                var existingImpl = @class.Methods.FirstOrDefault(
+                    m => m.OriginalName == method.OriginalName &&
                     m.Parameters.Where(p => !p.Ignore).SequenceEqual(
                         method.Parameters.Where(p => !p.Ignore),
-                            ParameterTypeComparer.Instance)))
+                        ParameterTypeComparer.Instance));
+                if (existingImpl != null)
+                {
+                    existingImpl.OriginalFunction = method;
                     continue;
+                }
                 var impl = new Method(method)
                     {
                         Namespace = @class,

tests/CSharp/CSharp.Tests.cs

@@ -647,6 +647,8 @@ public unsafe class CSharpTests : GeneratorTestFixture
         {
             Assert.That(implementsAbstractsFromPrimaryAndSecondary.AbstractInPrimaryBase, Is.EqualTo(101));
             Assert.That(implementsAbstractsFromPrimaryAndSecondary.AbstractInSecondaryBase, Is.EqualTo(5));
+            Assert.That(implementsAbstractsFromPrimaryAndSecondary.AbstractReturnsFieldInPrimaryBase, Is.EqualTo(201));
+            Assert.That(implementsAbstractsFromPrimaryAndSecondary.AbstractReturnsFieldInSecondaryBase, Is.EqualTo(202));
         }
     }
 

tests/CSharp/CSharp.cpp

@@ -1222,7 +1222,15 @@ void HasMissingObjectOnVirtualCall::setMissingObjectOnVirtualCall(MissingObjectO
     stackOverflowOnVirtualCall = value;
 }
 
-ImplementsAbstractsFromPrimaryAndSecondary::ImplementsAbstractsFromPrimaryAndSecondary()
+AbstractPrimaryBase::~AbstractPrimaryBase()
+{
+}
+
+AbstractSecondaryBase::~AbstractSecondaryBase()
+{
+}
+
+ImplementsAbstractsFromPrimaryAndSecondary::ImplementsAbstractsFromPrimaryAndSecondary() : field(200)
 {
 }
 
@@ -1239,3 +1247,13 @@ int ImplementsAbstractsFromPrimaryAndSecondary::abstractInSecondaryBase()
 {
     return 5;
 }
+
+int ImplementsAbstractsFromPrimaryAndSecondary::abstractReturnsFieldInPrimaryBase()
+{
+    return field + 1;
+}
+
+int ImplementsAbstractsFromPrimaryAndSecondary::abstractReturnsFieldInSecondaryBase()
+{
+    return field + 2;
+}

tests/CSharp/CSharp.h

@@ -1095,20 +1095,28 @@ private:
 class DLL_API AbstractPrimaryBase
 {
 public:
+    virtual ~AbstractPrimaryBase();
     virtual int abstractInPrimaryBase() = 0;
+    virtual int abstractReturnsFieldInPrimaryBase() = 0;
 };
 
 class DLL_API AbstractSecondaryBase
 {
 public:
+    virtual ~AbstractSecondaryBase();
     virtual int abstractInSecondaryBase() = 0;
+    virtual int abstractReturnsFieldInSecondaryBase() = 0;
 };
 
 class DLL_API ImplementsAbstractsFromPrimaryAndSecondary : public AbstractPrimaryBase, public AbstractSecondaryBase
 {
 public:
     ImplementsAbstractsFromPrimaryAndSecondary();
-    ~ImplementsAbstractsFromPrimaryAndSecondary();
+    virtual ~ImplementsAbstractsFromPrimaryAndSecondary();
     virtual int abstractInPrimaryBase();
     virtual int abstractInSecondaryBase();
+    virtual int abstractReturnsFieldInPrimaryBase();
+    virtual int abstractReturnsFieldInSecondaryBase();
+private:
+    int field;
 };