Added call to this.set.deepNormalize() to align with pattern generally

found in overwrites of Value#deepNormalize.


This omission surfaced through a race condition that led to a spurious
safety violation (#361):

1) A TLA+ spec defines a (zero-arity) operator s.a. "Foo == UNION {...}"
that appears in an invariant.

2) SpecProcessor#processConstantDefns eagerly evaluates the operator Foo
at startup and inserts its Value result UV into the corresponding node
of the semantic graph.

3) Two workers check if two states violate the invariant which triggers
UnionValue#member, which internally causes this.set to be normalized.
Since Value instances are not thread-safe because they are expected to
be fully normalized during state space exploration, the two workers race
to normalize this.set.

4) Worker A gets ahead and loops over the elements in UV#member while
worker B still normalizes UV. Worker A reads inconsistent data and thus
reports the invariant to be violated.

Thanks to Calvin Loncaric for suggesting this fix.

Fixes Github issue #361: UnionValue#deepNormalize omits to normalize set
leading to parallel TLC nondeterministically reporting spurious safety
violation
#361

[Bug][TLC]

tlatools/src/tlc2/TLC.java

@@ -78,7 +78,7 @@ public class TLC
 	private String metadir;
     /**
 	 * If instantiated with a non-Noop* instance, the trace will be written to the
-	 * user provided file (-dump paramter).
+	 * user provided file (-dump parameter).
 	 * <p>
 	 * Contrary to plain -dump, -dot will also write out transitions from state s to
 	 * s' if s' is already known. Thus, the resulting graph shows all successors of

tlatools/src/tlc2/value/impl/UnionValue.java

@@ -160,6 +160,23 @@ public final Value normalize() {
   @Override
   public final void deepNormalize() {
 	    try {
+			// MAK 09/17/2019: Added call to this.set.deepNormalize() to align with pattern
+			// generally found in overwrites of Value#deepNormalize.
+	    	// This omission surfaced through a race condition that led to a spurious
+	    	// safety violation (https://github.com/tlaplus/tlaplus/issues/361):
+	    	// 1) A TLA+ spec defines a (zero-arity) operator s.a. "Foo == UNION { ... }"
+	    	//    that appears in an invariant.
+	    	// 2) SpecProcessor#processConstantDefns eagerly evaluates the operator Foo at startup
+	    	//    and inserts its Value result UV into the corresponding node of the semantic graph.
+	    	// 3) Two workers check if two states violate the invariant which triggers UnionValue#member,
+	    	//    which internally causes this.set to be normalized.  Since Value instances are not thread-safe
+	    	//    because they are expected to be fully normalized during state space exploration, the
+	    	//    two workers race to normalize this.set.
+	    	// 4) Worker A gets ahead and loops over the elements in UV#member while worker B still normalizes UV.
+	    	//    Worker A reads inconsistent data and thus reports the invariant to be violated.
+	    	// Thanks to Calvin Loncaric for suggesting this fix.
+	    	this.set.deepNormalize();
+
       if (realSet == null) {
         realSet = SetEnumValue.DummyEnum;
       }

tlatools/test/tlc2/value/impl/DeepNormalizeValueTest.java

@@ -0,0 +1,54 @@
+/*******************************************************************************
+ * Copyright (c) 2019 Microsoft Research. All rights reserved. 
+ *
+ * The MIT License (MIT)
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy 
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is furnished to do
+ * so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software. 
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Contributors:
+ *   Markus Alexander Kuppe - initial API and implementation
+ ******************************************************************************/
+package tlc2.value.impl;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class DeepNormalizeValueTest {
+
+	/**
+	 * Test method for {@link tlc2.value.impl.UnionValue#deepNormalize()}.
+	 */
+	@Test
+	public void uv() {
+		final ValueVec vec = new ValueVec();
+		vec.addElement(new SetEnumValue(new IntValue[] {IntValue.gen(42)}, false));
+		vec.addElement(new SetEnumValue(new IntValue[] {IntValue.gen(23)}, false));
+		vec.addElement(new SetEnumValue(new IntValue[] {IntValue.gen(4711)}, false));
+		vec.addElement(new SetEnumValue(new IntValue[] {IntValue.gen(1)}, false));
+
+		final UnionValue uv = new UnionValue(new SetEnumValue(vec, false));
+		assertFalse(uv.isNormalized());
+		assertFalse(uv.set.isNormalized());
+
+		uv.deepNormalize();
+
+		assertTrue(uv.set.isNormalized());
+	}
+}