Fix Null Pointer Exception in EnhancedUnitGraph soot-oss#618

Author: ftc

src/main/java/soot/toolkits/graph/pdg/EnhancedUnitGraph.java

@@ -34,8 +34,8 @@
 import soot.jimple.ThrowStmt;
 import soot.jimple.internal.JNopStmt;
 import soot.toolkits.graph.DominatorNode;
-import soot.toolkits.graph.MHGDominatorsFinder;
 import soot.toolkits.graph.MHGPostDominatorsFinder;
+import soot.toolkits.graph.MHGDominatorsFinder;
 import soot.toolkits.graph.UnitGraph;
 import soot.util.Chain;
 
@@ -74,6 +74,11 @@ public EnhancedUnitGraph(Body body) {
     unitToSuccs = new HashMap<Unit, List<Unit>>(size * 2 + 1, 0.7f);
     unitToPreds = new HashMap<Unit, List<Unit>>(size * 2 + 1, 0.7f);
 
+    // Initialize all units in the unitToSuccs and unitsToPreds
+    for(Unit u : body.getUnits()){
+      unitToSuccs.put(u,new ArrayList<>());
+      unitToPreds.put(u,new ArrayList<>());
+    }
     /*
      * Compute the head and tails at each phase because other phases might rely on them.
      */

src/test/java/soot/toolkits/graph/EnhancedUnitGraphTest.java

@@ -0,0 +1,55 @@
+package soot.toolkits.graph;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import soot.*;
+import soot.options.Options;
+import soot.toolkits.graph.pdg.EnhancedUnitGraph;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+public class EnhancedUnitGraphTest {
+    private static EnhancedUnitGraphTestUtility testUtility;
+
+    private static String TARGET_CLASS = "soot.toolkits.graph.targets.TestException";
+    @BeforeClass
+    public static void setUp() throws IOException {
+        G.reset();
+        List<String> processDir = new ArrayList<>();
+        File f = new File("./target/test-classes");
+        if (f.exists()) {
+            processDir.add(f.getCanonicalPath());
+        }
+        Options.v().set_process_dir(processDir);
+
+        Options.v().set_src_prec(Options.src_prec_only_class);
+        Options.v().set_allow_phantom_refs(true);
+        Options.v().set_output_format(Options.output_format_none);
+        Scene.v().addBasicClass(TARGET_CLASS);
+        Scene.v().loadNecessaryClasses();
+        Options.v().set_prepend_classpath(true);
+        Scene.v().forceResolve("soot.toolkits.graph.targets.TestException", SootClass.BODIES);
+        testUtility = new EnhancedUnitGraphTestUtility();
+        PackManager.v().getPack("jtp")
+                .add(new Transform("jtp.TestEnhancedGraphUtility", testUtility));
+        PackManager.v().runPacks();
+    }
+
+    @Test
+    public void exceptionIsReachable(){
+
+        EnhancedUnitGraph unitGraph = testUtility.getUnitGraph();
+        UnitPatchingChain allUnits = unitGraph.body.getUnits();
+
+        int targetUnitsFound = 0;
+        for(Unit u : allUnits){
+            if(u.toString().contains("@caughtexception")){
+                assert(unitGraph.unitToPreds.get(u).size() > 0);
+                ++targetUnitsFound;
+            }
+        }
+        assert(targetUnitsFound == 2);
+    }
+}

src/test/java/soot/toolkits/graph/EnhancedUnitGraphTestUtility.java

@@ -0,0 +1,20 @@
+package soot.toolkits.graph;
+
+import soot.Body;
+import soot.BodyTransformer;
+import soot.toolkits.graph.pdg.EnhancedUnitGraph;
+
+public class EnhancedUnitGraphTestUtility extends BodyTransformer {
+    private EnhancedUnitGraph unitGraph = null;
+    protected void internalTransform(Body body, String phase, java.util.Map<String,String> options)
+    {
+        String methodSig = body.getMethod().getSignature();
+        if(methodSig.contains("soot.toolkits.graph.targets.TestException")
+                && body.getMethod().getName().contains("main"))
+            unitGraph = new EnhancedUnitGraph(body);
+    }
+
+    public EnhancedUnitGraph getUnitGraph() {
+        return unitGraph;
+    }
+}

src/test/java/soot/toolkits/graph/targets/TestException.java

@@ -0,0 +1,20 @@
+package soot.toolkits.graph.targets;
+
+public class TestException {
+
+    public static void main(String[] args) {
+        int a = 0;
+        int b = 0;
+
+        try {
+            a = a / b;
+        }
+        catch (Exception e) {
+            a = Math.abs(-1);
+        }
+        finally {
+            b = 0;
+        }
+    }
+
+}