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.

5 files changed, 27 insertions, 1 deletions

diff --git a/python/modules/IcePy/Communicator.cpp b/python/modules/IcePy/Communicator.cpp
index 7d7931e5f09..6ad3b3c2cf1 100644
--- a/python/modules/IcePy/Communicator.cpp
+++ b/python/modules/IcePy/Communicator.cpp
@@ -286,6 +286,9 @@ communicatorInit(CommunicatorObject* self, PyObject* args, PyObject* /*kwds*/)
 
     data.compactIdResolver = new IdResolver;
 
+    // Always accept cycles in Python
+    data.properties->setProperty("Ice.AcceptClassCycles", "1");
+
     Ice::CommunicatorPtr communicator;
     try
     {
diff --git a/python/test/Ice/admin/AllTests.py b/python/test/Ice/admin/AllTests.py
index 1e8e1cb72d9..a6ac1fcb2f8 100644
--- a/python/test/Ice/admin/AllTests.py
+++ b/python/test/Ice/admin/AllTests.py
@@ -183,12 +183,14 @@ def allTests(helper, communicator):
     # Test: PropertiesAdmin::getProperties()
     #
     pd = pa.getPropertiesForPrefix("")
-    test(len(pd) == 5)
+    test(len(pd) == 6)
     test(pd["Ice.Admin.Endpoints"] == "tcp -h 127.0.0.1")
     test(pd["Ice.Admin.InstanceName"] == "Test")
     test(pd["Prop1"] == "1")
     test(pd["Prop2"] == "2")
     test(pd["Prop3"] == "3")
+    # Ice for Python always sets Ice.AcceptClassCycles
+    test(pd["Ice.AcceptClassCycles"] == "1")
 
     changes = {}
 
diff --git a/python/test/Ice/objects/AllTests.py b/python/test/Ice/objects/AllTests.py
index 13dcef18c27..0cdcbd7d48d 100644
--- a/python/test/Ice/objects/AllTests.py
+++ b/python/test/Ice/objects/AllTests.py
@@ -357,4 +357,16 @@ def allTests(helper, communicator):
         test(f32.f2.ice_getIdentity().name == "F22")
     print("ok")
 
+    sys.stdout.write("testing sending class cycle... ")
+    sys.stdout.flush()
+    rec = Test.Recursive()
+    rec.v = rec
+    acceptsCycles = initial.acceptsClassCycles()
+    try:
+        initial.setCycle(rec)
+        test(acceptsCycles)
+    except Ice.UnknownLocalException:
+        test(not acceptsCycles)
+    print("ok")
+
     return initial
diff --git a/python/test/Ice/objects/Test.ice b/python/test/Ice/objects/Test.ice
index e6e4828ffb9..0acc2fd52a5 100644
--- a/python/test/Ice/objects/Test.ice
+++ b/python/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();
 
diff --git a/python/test/Ice/objects/TestI.py b/python/test/Ice/objects/TestI.py
index 7bebf279f22..82d868f0143 100644
--- a/python/test/Ice/objects/TestI.py
+++ b/python/test/Ice/objects/TestI.py
@@ -126,6 +126,12 @@ class InitialI(Test.Initial):
     def supportsClassGraphDepthMax(self, current):
         return True
 
+    def setCycle(self, r, current):
+        pass
+
+    def acceptsClassCycles(self, current):
+        return True
+
     def getMB(self, current):
         return Test.Initial.GetMBMarshaledResult(self._b1, current)