java.util.ConcurrentModificationException
   at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
   at java.util.ArrayList$Itr.next(ArrayList.java:851)
   at org.netbeans.modules.cnd.debugger.gdb2.GdbDebuggerImpl.retryWatches(GdbDebuggerImpl.java:3115)
   at org.netbeans.modules.cnd.debugger.gdb2.GdbDebuggerImpl.updateWatches(GdbDebuggerImpl.java:3128)
   at org.netbeans.modules.cnd.debugger.gdb2.GdbDebuggerImpl.genericStoppedWithSrc(GdbDebuggerImpl.java:3964)
   at org.netbeans.modules.cnd.debugger.gdb2.GdbDebuggerImpl.access$5900(GdbDebuggerImpl.java:150)
   at org.netbeans.modules.cnd.debugger.gdb2.GdbDebuggerImpl$40.onDone(GdbDebuggerImpl.java:4194)
   at org.netbeans.modules.cnd.debugger.gdb2.mi.MICommandManager.dispatch(MICommandManager.java:194)
   at org.netbeans.modules.cnd.debugger.gdb2.mi.MIProxy.dispatch(MIProxy.java:188)
   at org.netbeans.modules.cnd.debugger.gdb2.Gdb$MyMIProxy.dispatch(Gdb.java:697)
   at org.netbeans.modules.cnd.debugger.gdb2.mi.MIProxy.result(MIProxy.java:193)
   at org.netbeans.modules.cnd.debugger.gdb2.mi.MIProxy.processLine(MIProxy.java:157)
Caused: java.lang.Exception: when processing line: 631^done,stack=[frame={level="0",addr="0x000000000040b9d8",func="Movable::world",file="Movable.cpp",fullname="/home/al/dev/cpp/workspace/Mark III/Movable.cpp",line="34"},frame={level="1",addr="0x00007fffffff43ff",func="<function called from gdb>"},frame={level="2",addr="0x000000000040b9d8",func="Movable::world",file="Movable.cpp",fullname="/home/al/dev/cpp/workspace/Mark III/Movable.cpp",line="34"},frame={level="3",addr="0x00007fffffff449f",func="<function called from gdb>"},frame={level="4",addr="0x000000000040b9d8",func="Movable::world",file="Movable.cpp",fullname="/home/al/dev/cpp/workspace/Mark III/Movable.cpp",line="34"},frame={level="5",addr="0x00007fffffff453f",func="<function called from gdb>"},frame={level="6",addr="0x000000000040b9d8",func="Movable::world",file="Movable.cpp",fullname="/home/al/dev/cpp/workspace/Mark III/Movable.cpp",line="34"},frame={level="7",addr="0x00007fffffff45df",func="<function called from gdb>"},frame={level="8",addr="0x000000000040
   at org.netbeans.modules.cnd.debugger.gdb2.Tap$4.run(Tap.java:355)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1443)
   at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:68)
   at org.openide.util.lookup.Lookups.executeWith(Lookups.java:303)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2058)