Added PYTHONNET_GC_DEBUG environment variable option for debugging GC…

… related errors.
pythonnet · dmitriyse · Aug 31, 2017 · Sep 2, 2017 · Sep 2, 2017 · Sep 2, 2017
commit 66fc91b9eb946e41d7c355bfa1fbbac73baedf3d
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -24,6 +24,8 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
 
 ### Fixed
 -   Fixed memory leaks, caused by non-working PyObject, PythonException, DelecateManager->Dispatcher finalizers.
+    Set environment variable PYTHONNET_GC_DEBUG=1 to force full GC on each PythonEngine.Shutdown, this allows 
+    to esily detect GC related bugs.
 -   Fixed secondary PythonEngine.Initialize call, all sensitive static variables now reseted.
     This is a hidden bug. Once python cleaning up enough memory, objects from previous engine run becomes corrupted.
 -   Fixed Visual Studio 2017 compat (#434) for setup.py

diff --git a/src/runtime/pythonengine.cs b/src/runtime/pythonengine.cs
@@ -4,6 +4,7 @@
 using System.Linq;
 using System.Reflection;
 using System.Runtime.InteropServices;
+using System.Threading;
 
 namespace Python.Runtime
 {
@@ -17,6 +18,12 @@ public class PythonEngine : IDisposable
         private static IntPtr _pythonHome = IntPtr.Zero;
         private static IntPtr _programName = IntPtr.Zero;
         private static IntPtr _pythonPath = IntPtr.Zero;
+        private static bool _isGcDebugEnabled;
+
+        static PythonEngine()
+        {
+            _isGcDebugEnabled = !String.IsNullOrWhiteSpace(Environment.GetEnvironmentVariable("PYTHONNET_GC_DEBUG"));
+        }
 
         public PythonEngine()
         {
@@ -298,9 +305,25 @@ public static void Shutdown()
         {
             if (initialized)
             {
+
+                if (_isGcDebugEnabled)
+                {
+                    GC.Collect();
+                    GC.WaitForPendingFinalizers();
+                    Thread.Sleep(100);
+                }
+
                 CurrentRefDecrementer?.Dispose();
                 CurrentRefDecrementer = null;
 
+                if (_isGcDebugEnabled)
+                {
+                    GC.Collect();
+                    GC.WaitForPendingFinalizers();
+                    Thread.Sleep(100);
+                }
+
+
                 PyScopeManager.Global.Clear();
                 // We should not release memory for variables that can be used without initialized python engine.
                 // It's assumed that Py_GetPythonHome returns valid string without engine initialize. Py_GetPythonHome will always return the