Restrict first garbage collection

Otherwise, collecting all at this earlier point results in corrupt memory for derived types.

Author: Frawak

src/runtime/Finalizer.cs

@@ -191,7 +191,7 @@ internal static void Shutdown()
             Instance.started = false;
         }
 
-        internal nint DisposeAll()
+        internal nint DisposeAll(bool disposeObj = true, bool disposeDerived = true, bool disposeBuffer = true)
         {
             if (_objQueue.IsEmpty && _derivedQueue.IsEmpty && _bufferQueue.IsEmpty)
                 return 0;
@@ -216,7 +216,7 @@ internal nint DisposeAll()
 
                 try
                 {
-                    while (!_objQueue.IsEmpty)
+                    if (disposeObj) while (!_objQueue.IsEmpty)
                     {
                         if (!_objQueue.TryDequeue(out var obj))
                             continue;
@@ -240,7 +240,7 @@ internal nint DisposeAll()
                         }
                     }
 
-                    while (!_derivedQueue.IsEmpty)
+                    if (disposeDerived) while (!_derivedQueue.IsEmpty)
                     {
                         if (!_derivedQueue.TryDequeue(out var derived))
                             continue;
@@ -258,7 +258,7 @@ internal nint DisposeAll()
                         collected++;
                     }
 
-                    while (!_bufferQueue.IsEmpty)
+                    if (disposeBuffer) while (!_bufferQueue.IsEmpty)
                     {
                         if (!_bufferQueue.TryDequeue(out var buffer))
                             continue;

src/runtime/Runtime.cs

@@ -278,7 +278,8 @@ internal static void Shutdown()
             ClearClrModules();
             RemoveClrRootModule();
 
-            TryCollectingGarbage(MaxCollectRetriesOnShutdown, forceBreakLoops: true);
+            TryCollectingGarbage(MaxCollectRetriesOnShutdown, forceBreakLoops: true,
+                                 obj: true, derived: false, buffer: false);
 
             NullGCHandles(ExtensionType.loadedExtensions);
             ClassManager.RemoveClasses();
@@ -329,7 +330,8 @@ internal static void Shutdown()
 
         const int MaxCollectRetriesOnShutdown = 20;
         internal static int _collected;
-        static bool TryCollectingGarbage(int runs, bool forceBreakLoops)
+        static bool TryCollectingGarbage(int runs, bool forceBreakLoops,
+                                         bool obj = true, bool derived = true, bool buffer = true)
         {
             if (runs <= 0) throw new ArgumentOutOfRangeException(nameof(runs));
 
@@ -342,7 +344,9 @@ static bool TryCollectingGarbage(int runs, bool forceBreakLoops)
                     GC.Collect();
                     GC.WaitForPendingFinalizers();
                     pyCollected += PyGC_Collect();
-                    pyCollected += Finalizer.Instance.DisposeAll();
+                    pyCollected += Finalizer.Instance.DisposeAll(disposeObj: obj,
+                                                                 disposeDerived: derived,
+                                                                 disposeBuffer: buffer);
                 }
                 if (Volatile.Read(ref _collected) == 0 && pyCollected == 0)
                 {