Don't choke as much on malformed data

Author: SamboyCoding

UMS.Analysis/SnapshotFile.cs

@@ -134,15 +134,21 @@ public RawManagedObjectInfo ParseManagedObjectInfo(ulong address)
                 return new();
 
             info.TypeInfoAddress = ReadPointer(typeInfoSpan);
-            TypeIndicesByPointer.TryGetValue(info.TypeInfoAddress, out info.TypeDescriptionIndex);
-
-            if (!info.IsKnownType)
-                throw new($"Failed to resolve type for object at {address:X}");
+            if (!TypeIndicesByPointer.TryGetValue(info.TypeInfoAddress, out info.TypeDescriptionIndex) || !info.IsKnownType)
+            {
+                Console.WriteLine($"WARNING: Failed to resolve type for object at {address:X}");
+                
+                //Cache the failure - let's not waste time.
+                ret = _managedObjectInfoCache[address] = new();
+                return ret;
+            }
         }
 
         var typeIndex = info.TypeDescriptionIndex;
         info.Flags = GetTypeFlagsByIndex(typeIndex);
         info.Size = SizeOfObjectInBytes(info, heap);
+        if (info.Size == 0)
+            throw new("Size 0?");
         info.Data = heap[..info.Size].ToArray();
         info.SelfAddress = address;
 
@@ -190,8 +196,8 @@ private int GetObjectSizeFromArrayInBytes(RawManagedObjectInfo info, Span<byte>
 
         if (arrayLength > heap.Length)
         {
-            Console.WriteLine($"Warning: Skipping unreasonable array length {arrayLength}");
-            return VirtualMachineInformation.ArrayHeaderSize; //Sanity bailout
+            Console.WriteLine($"Warning: Reducing array length {arrayLength} to {heap.Length} because the heap doesn't contain all the data.");
+            return heap.Length; //Sanity bailout
         }
 
         //Need to check if the array element type is a value type

UMS.Analysis/Structures/Objects/ManagedClassInstance.cs

@@ -100,6 +100,8 @@ public ManagedClassInstance(SnapshotFile file, RawManagedObjectInfo info, Manage
             var elementTypeSize = (elementFlags & TypeFlags.ValueType) != 0 ? file.GetTypeDescriptionSizeBytes(elementType.TypeIndex) : 8;
             var arrayData = info.Data.AsSpan(file.VirtualMachineInformation.ArrayHeaderSize..);
 
+            arrayElementCount = Math.Min(arrayElementCount, arrayData.Length / elementTypeSize); //Just in case the array length is wrong
+
             Fields = new IFieldValue[arrayElementCount];
             for (var i = 0; i < arrayElementCount; i++)
             {
@@ -304,7 +306,7 @@ public bool IsLeakedManagedShell(SnapshotFile file)
             var basicFieldInfoCache = fields[fieldNumber];
             var name = file.GetFieldName(basicFieldInfoCache.FieldIndex);
 
-            if (name == "m_CachedPtr")
+            if (name == "m_CachedPtr" && Fields.Length > fieldNumber)
             {
                 var value = Fields[fieldNumber];