Added inline comment about dangers of multidomain usage

JanKrivanek · filmor · commit 677281e3d115 · 2018-10-16T11:24:17.000+02:00
As requested here: #538 (comment)
diff --git a/AUTHORS.md b/AUTHORS.md
@@ -26,6 +26,7 @@
 -   Dmitriy Se ([@dmitriyse](https://github.com/dmitriyse))
 -   He-chien Tsai ([@t3476](https://github.com/t3476))
 -   Ivan Cronyn ([@cronan](https://github.com/cronan))
+-   Jan Krivanek ([@jakrivan](https://github.com/jakrivan))
 -   Jeff Reback ([@jreback](https://github.com/jreback))
 -   Joe Frayne ([@jfrayne](https://github.com/jfrayne))
 -   John Burnett ([@johnburnett](https://github.com/johnburnett))
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -19,6 +19,7 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
 -   Catches exceptions thrown in C# iterators (yield returns) and rethrows them in python ([#475][i475])([#693][p693])
 -   Implemented GetDynamicMemberNames() for PyObject to allow dynamic object members to be visible in the debugger ([#443][i443])([#690][p690])
 -   Incorporated reference-style links to issues and pull requests in the CHANGELOG ([#608][i608])
+-   Added detailed comments about aproaches and dangers to handle multi-app-domains ([#625][p625])
 
 ### Changed
 
@@ -683,4 +684,5 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
 [p225]: https://github.com/pythonnet/pythonnet/pull/225
 [p78]: https://github.com/pythonnet/pythonnet/pull/78
 [p163]: https://github.com/pythonnet/pythonnet/pull/163
+[p625]: https://github.com/pythonnet/pythonnet/pull/625
 [i131]: https://github.com/pythonnet/pythonnet/issues/131
diff --git a/src/runtime/assemblymanager.cs b/src/runtime/assemblymanager.cs
@@ -17,7 +17,15 @@ internal class AssemblyManager
     {
         // modified from event handlers below, potentially triggered from different .NET threads
         // therefore this should be a ConcurrentDictionary
+        //
+        // WARNING: Dangerous if cross-app domain usage is ever supported
+        //    Reusing the dictionary with assemblies accross multiple initializations is problematic. 
+        //    Loading happens from CurrentDomain (see line 53). And if the first call is from AppDomain that is later unloaded, 
+        //    than it can end up referring to assemblies that are already unloaded (default behavior after unload appDomain - 
+        //     unless LoaderOptimization.MultiDomain is used);
+        //    So for multidomain support it is better to have the dict. recreated for each app-domain initialization
         private static ConcurrentDictionary<string, ConcurrentDictionary<Assembly, string>> namespaces;
+
         //private static Dictionary<string, Dictionary<string, string>> generics;
         private static AssemblyLoadEventHandler lhandler;
         private static ResolveEventHandler rhandler;
