Bring back blob disposal checks

src/Avalonia.Base/Platform/Internal/UnmanagedBlob.cs

@@ -1,5 +1,8 @@
 using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
+using System.Threading;
 
 namespace Avalonia.Platform.Internal;
 
@@ -7,7 +10,30 @@ internal class UnmanagedBlob : IUnmanagedBlob
 {
     private IntPtr _address;
     private readonly object _lock = new object();
-    
+#if DEBUG
+    private static readonly List<string> Backtraces = new List<string>();
+    private static Thread? GCThread;
+    private readonly string _backtrace;
+    private static readonly object _btlock = new object();
+
+    class GCThreadDetector
+    {
+        ~GCThreadDetector()
+        {
+            GCThread = Thread.CurrentThread;
+        }
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static void Spawn() => new GCThreadDetector();
+
+    static UnmanagedBlob()
+    {
+        Spawn();
+        GC.WaitForPendingFinalizers();
+    }
+#endif
+
     public UnmanagedBlob(int size)
     {
         try
@@ -23,14 +49,23 @@ internal class UnmanagedBlob : IUnmanagedBlob
             GC.SuppressFinalize(this);
             throw;
         }
+#if DEBUG
+        _backtrace = Environment.StackTrace;
+        lock (_btlock)
+            Backtraces.Add(_backtrace);
+#endif
     }
-    
-    private void DoDispose()
+
+    void DoDispose()
     {
         lock (_lock)
         {
             if (!IsDisposed)
             {
+#if DEBUG
+                lock (_btlock)
+                    Backtraces.Remove(_backtrace);
+#endif
                 Marshal.FreeHGlobal(_address);
                 GC.RemoveMemoryPressure(Size);
                 IsDisposed = true;
@@ -39,18 +74,35 @@ internal class UnmanagedBlob : IUnmanagedBlob
             }
         }
     }
-    
+
     public void Dispose()
     {
+#if DEBUG
+        if (Thread.CurrentThread.ManagedThreadId == GCThread?.ManagedThreadId)
+        {
+            lock (_lock)
+            {
+                if (!IsDisposed)
+                {
+                    Console.Error.WriteLine("Native blob disposal from finalizer thread\nBacktrace: "
+                                         + Environment.StackTrace
+                                         + "\n\nBlob created by " + _backtrace);
+                }
+            }
+        }
+#endif
         DoDispose();
         GC.SuppressFinalize(this);
     }
-    
+
     ~UnmanagedBlob()
     {
+#if DEBUG
+        Console.Error.WriteLine("Undisposed native blob created by " + _backtrace);
+#endif
         DoDispose();
     }
-    
+
     public IntPtr Address => IsDisposed ? throw new ObjectDisposedException("UnmanagedBlob") : _address;
     public int Size { get; private set; }
     public bool IsDisposed { get; private set; }