(1) Enabled support for building with VS 2015. (2) Added tunload to unload

tasks from command line. (3) Fixed memory leak in maps due to threadlocal
storage; replaced with spinlocks for thread-safe reads.

Bld/FormulaBuild/FormulaBuild/SourceDownloader.cs

@@ -264,6 +264,18 @@
                 var subKey = Environment.Is64BitOperatingSystem ? RegVS64SubKey : RegVS32SubKey;
 
                 string installDir = null;
+                //// Try to get version 14
+                if (installDir == null)
+                {
+                    using (var key = Registry.LocalMachine.OpenSubKey(string.Format(subKey, 14)))
+                    {
+                        if (key != null)
+                        {
+                            installDir = key.GetValue("ProductDir") as string;
+                        }
+                    }
+                }
+
                 //// Try to get version 12
                 if (installDir == null)
                 {

Src/CommandLine/CommandInterface.cs

@@ -36,8 +36,9 @@
         private const string SaveMsg = "Saves the module modname into file.";
         private const string LSInfoMsg = "Lists environment objects. Use: ls [vars | progs | tasks]";
         private const string LoadMsg = "Loads and compiles a file that is not yet loaded. Use: load filename";
-        private const string UnloadMsg = "Unloads and an installed program and all dependent programs. Use: unload [prog | *]";
-        private const string ReloadMsg = "Reloads and an installed program and all dependent programs. Use: reload [prog | *]";
+        private const string UnloadMsg = "Unloads an installed program and all dependent programs. Use: unload [prog | *]";
+        private const string TUnloadMsg = "Unloads a task. Use: tunload [id | *]";
+        private const string ReloadMsg = "Reloads an installed program and all dependent programs. Use: reload [prog | *]";
         private const string PrintMsg = "Prints the installed program with the given name. Use: print progname";
         private const string DetailsMsg = "Prints details about the compiled module with the given name. Use: det modname";
         private const string TypesMsg = "Prints inferred variable types. Use: types modname";
@@ -225,6 +226,10 @@
             cmdMap.Add(ulCmd.Name, ulCmd);
             cmdMap.Add(ulCmd.ShortName, ulCmd);
 
+            var tulCmd = new Command("tunload", "tul", DoTUnload, TUnloadMsg);
+            cmdMap.Add(tulCmd.Name, tulCmd);
+            cmdMap.Add(tulCmd.ShortName, tulCmd);
+
             var rlCmd = new Command("reload", "rl", DoReload, ReloadMsg);
             cmdMap.Add(rlCmd.Name, rlCmd);
             cmdMap.Add(rlCmd.ShortName, rlCmd);
@@ -505,6 +510,29 @@
             }
         }
 
+        private void DoTUnload(string s)
+        {
+            s = s.Trim();
+            int taskId;
+            if (!int.TryParse(s, out taskId) && s != "*")
+            {
+                sink.WriteMessageLine(TUnloadMsg, SeverityKind.Warning);
+            }
+            else if (s == "*")
+            {
+                var cnt = taskManager.UnloadTasks();
+                sink.WriteMessageLine(string.Format("Unloaded {0} tasks", cnt));
+            }
+            else if (taskManager.TryUnloadTask(taskId))
+            {
+                sink.WriteMessageLine(string.Format("Unloaded task {0}", taskId));
+            }
+            else
+            {
+                sink.WriteMessageLine(string.Format("No task with ID {0}", taskId), SeverityKind.Warning);
+            }
+        }
+
         private void DoStats(string s)
         {
             var cmdParts = s.Split(cmdSplitChars, 2, StringSplitOptions.RemoveEmptyEntries);

Src/CommandLine/TaskManager.cs

@@ -47,6 +47,26 @@
             return true;
         }
 
+        public int UnloadTasks()
+        {
+            var unloadCount = tasks.Count;
+            tasks.Clear();
+            GC.Collect();
+            return unloadCount;
+        }
+
+        public bool TryUnloadTask(int id)
+        {
+            if (!tasks.ContainsKey(id))
+            {
+                return false;
+            }
+
+            tasks.Remove(id);
+            GC.Collect();
+            return true;
+        }
+
         public bool TryGetStatistics(int id, out ExecuterStatistics stats)
         {
             TaskData data;

Src/Core/API/Base/Env.cs

@@ -1292,6 +1292,8 @@
             programDeps = nextDeps;
             FileRoot = newFileRoot;
             EnvRoot = newEnvRoot;
+
+            GC.Collect();
         }
 
         private IEnumerable<ProgramName> EnumeratePrograms(DependencyCollection<ProgramName, Unit>.IDependencyNode n)

Src/Core/Common/Map.cs

@@ -11,9 +11,10 @@
     /// </summary>
     public class Map<S, T> : IEnumerable<KeyValuePair<S, T>>
     {
-        private Comparison<S> comparer;
+        private SpinLock lastFoundLock = new SpinLock();
+        private Node lastFoundNode = null;
 
-        private ThreadLocal<Node> lastFound = new ThreadLocal<Node>();
+        private Comparison<S> comparer;
 
         private int numberOfKeys = 0;
 
@@ -21,6 +22,43 @@
 
         private Node root = null;
 
+        private Node LastFound
+        {
+            get
+            {
+                bool gotLock = false;
+                try
+                {
+                    lastFoundLock.Enter(ref gotLock);
+                    return lastFoundNode;
+                }
+                finally
+                {
+                    if (gotLock)
+                    {
+                        lastFoundLock.Exit();
+                    }
+                }
+            }
+
+            set
+            {
+                bool gotLock = false;
+                try
+                {
+                    lastFoundLock.Enter(ref gotLock);
+                    lastFoundNode = value;
+                }
+                finally
+                {
+                    if (gotLock)
+                    {
+                        lastFoundLock.Exit();
+                    }
+                }
+            }
+        }
+
         public Map(Comparison<S> comparer)
         {
             this.comparer = comparer;
@@ -187,7 +225,7 @@
             numberOfKeys = 0;
             phantomList.Clear();
             root = null;
-            lastFound.Value = null;
+            LastFound = null;
         }
 
         [Pure]
@@ -413,9 +451,11 @@
 
         public bool TryFindValue(S key, out T value)
         {
-            if (lastFound.Value != null && Compare(lastFound.Value, key) == 0)
+            var lastFound = LastFound;
+
+            if (lastFound != null && Compare(lastFound, key) == 0)
             {
-                value = lastFound.Value.Value;
+                value = lastFound.Value;
                 return true;
             }
 
@@ -427,7 +467,7 @@
                 if (cmp == 0)
                 {
                     value = checkNode.Value;
-                    lastFound.Value = checkNode;
+                    LastFound = checkNode;
                     return true;
                 }
                 else if (cmp > 0)
@@ -446,7 +486,7 @@
 
         public bool Remove(S key)
         {
-            lastFound.Value = null;
+            LastFound = null;
             Node deletePos = FindNearestNode(key);
             if (deletePos == null || Compare(deletePos, key) != 0)
             {

Src/Core/Common/Terms/SubtermMatcher.cs

@@ -73,8 +73,10 @@
 
         public SubtermMatcher(TermIndex index, bool onlyNewKinds, Term[] pattern)
         {
-            Contract.Requires(index != null);
             Contract.Requires(pattern != null && pattern.Length > 0);
+            //// Appears that Requires is triggering bug in Code Contracts 1.9.10714.2
+            Contract.Assert(index != null);
+
             this.pattern = pattern;
             IsMatchOnlyNewKinds = onlyNewKinds;
             matchingUnions = new AppFreeCanUnn[pattern.Length];