Bugfix for concurrent Context creation in Java and .NET.

Relates to #205 #245

src/api/dotnet/Context.cs

@@ -36,10 +36,13 @@ namespace Microsoft.Z3
         /// </summary>
         public Context()
             : base()
+        {
+            lock (creation_lock)
             {
                 m_ctx = Native.Z3_mk_context_rc(IntPtr.Zero);
                 InitContext();
             }
+        }
 
         /// <summary>
         /// Constructor.
@@ -64,6 +67,8 @@ namespace Microsoft.Z3
         {
             Contract.Requires(settings != null);
 
+            lock (creation_lock)
+            {
                 IntPtr cfg = Native.Z3_mk_config();
                 foreach (KeyValuePair<string, string> kv in settings)
                     Native.Z3_set_param_value(cfg, kv.Key, kv.Value);
@@ -71,6 +76,7 @@ namespace Microsoft.Z3
                 Native.Z3_del_config(cfg);
                 InitContext();
             }
+        }
         #endregion
 
         #region Symbols
@@ -4381,6 +4387,7 @@ namespace Microsoft.Z3
         #region Internal
         internal IntPtr m_ctx = IntPtr.Zero;
         internal Native.Z3_error_handler m_n_err_handler = null;
+        internal static Object creation_lock = new Object();
         internal IntPtr nCtx { get { return m_ctx; } }
 
         internal void NativeErrorHandler(IntPtr ctx, Z3_error_code errorCode)

src/api/java/Context.java

@@ -32,9 +32,11 @@ public class Context extends IDisposable
     public Context()
     {        
         super();
+        synchronized (creation_lock) {            
             m_ctx = Native.mkContextRc(0);
             initContext();
         }
+    }
 
     /**
      * Constructor.
@@ -56,6 +58,7 @@ public class Context extends IDisposable
     public Context(Map<String, String> settings)
     {
         super();
+        synchronized (creation_lock) {            
             long cfg = Native.mkConfig();
             for (Map.Entry<String, String> kv : settings.entrySet())
                 Native.setParamValue(cfg, kv.getKey(), kv.getValue());
@@ -63,6 +66,7 @@ public class Context extends IDisposable
             Native.delConfig(cfg);
             initContext();
         }
+    }
 
     /**
      * Creates a new symbol using an integer. 
@@ -3638,7 +3642,8 @@ public class Context extends IDisposable
         Native.updateParamValue(nCtx(), id, value);
     }
 
-    long m_ctx = 0;
+    protected long m_ctx = 0;
+    protected static Object creation_lock = new Object();
 
     long nCtx()
     {

src/api/java/InterpolationContext.java

@@ -35,9 +35,12 @@ public class InterpolationContext extends Context
      **/
     public InterpolationContext()
     {
+        super();
+        synchronized(creation_lock) {
             m_ctx = Native.mkInterpolationContext(0);
             initContext(); 
         }
+    }
 
     /** 
      * Constructor.
@@ -48,6 +51,8 @@ public class InterpolationContext extends Context
      **/
     public InterpolationContext(Map<String, String> settings)
     { 
+        super();
+        synchronized(creation_lock) {
             long cfg = Native.mkConfig();
             for (Map.Entry<String, String> kv : settings.entrySet())
                 Native.setParamValue(cfg, kv.getKey(), kv.getValue());
@@ -55,6 +60,7 @@ public class InterpolationContext extends Context
             Native.delConfig(cfg);
             initContext();
         }
+    }
 
     /** 
       * Create an expression that marks a formula position for interpolation.