From ffdf1273de812a45f240f21ed17e040f40b6142d Mon Sep 17 00:00:00 2001
From: Sam Harwell <sam@tunnelvisionlabs.com>
Date: Fri, 20 Feb 2015 07:39:31 -0600
Subject: [PATCH] Fix expression evaluation when toString() returns null

Fixes #29
---
 .../ObjectReference.cs                        |  4 +++
 .../Debugger/JavaDebugProperty.cs             | 26 +++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/Tvl.Java.DebugInterface.Client/ObjectReference.cs b/Tvl.Java.DebugInterface.Client/ObjectReference.cs
index bbf4ebb2..a72e83b8 100644
--- a/Tvl.Java.DebugInterface.Client/ObjectReference.cs
+++ b/Tvl.Java.DebugInterface.Client/ObjectReference.cs
@@ -118,6 +118,10 @@ public IStrongValueHandle<IValue> InvokeMethod(IThreadReference thread, IMethod
                 throw new NotImplementedException();
             }
 
+            Value returnValueMirror = VirtualMachine.GetMirrorOf(returnValue);
+            if (returnValueMirror == null)
+                return null;
+
             return new StrongValueHandle<Value>(VirtualMachine.GetMirrorOf(returnValue));
         }
 
diff --git a/Tvl.VisualStudio.Language.Java/Debugger/JavaDebugProperty.cs b/Tvl.VisualStudio.Language.Java/Debugger/JavaDebugProperty.cs
index aa36a794..0b7b780c 100644
--- a/Tvl.VisualStudio.Language.Java/Debugger/JavaDebugProperty.cs
+++ b/Tvl.VisualStudio.Language.Java/Debugger/JavaDebugProperty.cs
@@ -629,6 +629,32 @@ public int GetPropertyInfo(enum_DEBUGPROP_INFO_FLAGS dwFields, uint dwRadix, uin
                                                 displayValue = stringReference.GetValue();
                                         }
                                     }
+
+                                    if (displayValue == null)
+                                    {
+                                        IClassType objectClass = classType;
+                                        while (true)
+                                        {
+                                            IClassType parentClass = objectClass.GetSuperclass();
+                                            if (parentClass != null)
+                                                objectClass = parentClass;
+                                            else
+                                                break;
+                                        }
+
+                                        IMethod objectToStringMethod = objectClass.GetConcreteMethod("toString", "()Ljava/lang/String;");
+
+                                        // fall back to a non-virtual call
+                                        using (IStrongValueHandle<IValue> result = objectReference.InvokeMethod(null, objectToStringMethod, InvokeOptions.NonVirtual | InvokeOptions.SingleThreaded))
+                                        {
+                                            if (result != null)
+                                            {
+                                                stringReference = result.Value as IStringReference;
+                                                if (stringReference != null)
+                                                    displayValue = stringReference.GetValue();
+                                            }
+                                        }
+                                    }
                                 }
 
                                 pPropertyInfo[0].bstrValue = "{" + displayValue + "}";