Add class cycle detection during unmarshaling (#946)

Add support for detection of class cycles during unmarshaling in
languages which do no have garbage collection: C++, Swift, and Objective-C.
A `MarshalException` is thrown when a cycle is detected.

The property `Ice.AcceptClassCycles` can be set to a value greater than `0`
to change this behavior.

4 files changed, 33 insertions, 1 deletions

diff --git a/csharp/src/Ice/PropertyNames.cs b/csharp/src/Ice/PropertyNames.cs
index a4b0440ead6..d8926852333 100644
--- a/csharp/src/Ice/PropertyNames.cs
+++ b/csharp/src/Ice/PropertyNames.cs
@@ -1,7 +1,7 @@
 //
 // Copyright (c) ZeroC, Inc. All rights reserved.
 //
-// Generated by makeprops.py from file ./config/PropertyNames.xml, Fri Sep  6 18:11:04 2019
+// Generated by makeprops.py from file ./config/PropertyNames.xml, Thu Jul  2 14:55:02 2020
 
 // IMPORTANT: Do not edit this file -- any edits made here will be lost!
 
@@ -11,6 +11,7 @@ namespace IceInternal
     {
         public static Property[] IceProps =
         {
+             new Property(@"^Ice\.AcceptClassCycles$", false, null),
              new Property(@"^Ice\.ACM\.Client$", true, null),
              new Property(@"^Ice\.ACM\.Server$", true, null),
              new Property(@"^Ice\.ACM\.Timeout$", false, null),
diff --git a/csharp/test/Ice/objects/AllTests.cs b/csharp/test/Ice/objects/AllTests.cs
index d0cfb08c6ba..abfa3785dc0 100644
--- a/csharp/test/Ice/objects/AllTests.cs
+++ b/csharp/test/Ice/objects/AllTests.cs
@@ -538,6 +538,25 @@ namespace Ice
                     }
                     output.WriteLine("ok");
 
+                    output.Write("testing sending class cycle... ");
+                    output.Flush();
+                    {
+                        var rec = new Test.Recursive();
+                        rec.v = rec;
+                        var acceptsCycles = initial.acceptsClassCycles();
+                        try
+                        {
+                            initial.setCycle(rec);
+                            test(acceptsCycles);
+                        }
+                        catch(Ice.UnknownLocalException)
+                        {
+                            test(!acceptsCycles);
+                        }
+
+                    }
+                    output.WriteLine("ok");
+
                     return initial;
                 }
             }
diff --git a/csharp/test/Ice/objects/InitialI.cs b/csharp/test/Ice/objects/InitialI.cs
index 19e34a228d8..0aa1a0451f6 100644
--- a/csharp/test/Ice/objects/InitialI.cs
+++ b/csharp/test/Ice/objects/InitialI.cs
@@ -123,6 +123,15 @@ namespace Ice
                 return true;
             }
 
+            public override void setCycle(Test.Recursive r, Ice.Current current)
+            {
+            }
+
+            public override bool acceptsClassCycles(Ice.Current current)
+            {
+                return true;
+            }
+
             public override Test.D1 getD1(Test.D1 d1, Ice.Current current)
             {
                 return d1;
diff --git a/csharp/test/Ice/objects/Test.ice b/csharp/test/Ice/objects/Test.ice
index 9fda575741c..9bcea5b2eaa 100644
--- a/csharp/test/Ice/objects/Test.ice
+++ b/csharp/test/Ice/objects/Test.ice
@@ -216,6 +216,9 @@ interface Initial
     void setRecursive(Recursive p);
     bool supportsClassGraphDepthMax();
 
+    void setCycle(Recursive r);
+    bool acceptsClassCycles();
+
     ["marshaled-result"] B getMB();
     ["amd", "marshaled-result"] B getAMDMB();