Properly handle static interface methods as entrypoints (#1275)

When a static Interface method is selected as an Entrypoint, WALA
creates an invokeinterface instead of an invokestatic instruction in
FakeRootMethod. This will lead to an out-of-array read when resolving
the receiver for an interface invocation.

A test can be simply an Android app generated by Android Studio for a
Basic Activity demo (either Java or Kotlin). In my case, the problem
occurs for handling:

40149 = invokeinterface < Application,
Landroidx/window/layout/WindowMetricsCalculator,
getOrCreate()Landroidx/window/layout/WindowMetricsCalculator; > @32353
exception:40150

And the exception is as follows:

java.lang.ArrayIndexOutOfBoundsException: Index 0 out of bounds for
length 0
at
com.ibm.wala.ipa.callgraph.propagation.SSAPropagationCallGraphBuilder.lambda$getTargetsForCall$0(SSAPropagationCallGraphBuilder.java:2072)
at
com.ibm.wala.ipa.callgraph.propagation.SSAPropagationCallGraphBuilder$CrossProductRec.rec(SSAPropagationCallGraphBuilder.java:542)
at
com.ibm.wala.ipa.callgraph.propagation.SSAPropagationCallGraphBuilder.iterateCrossProduct(SSAPropagationCallGraphBuilder.java:2055)
at
com.ibm.wala.ipa.callgraph.propagation.SSAPropagationCallGraphBuilder.getTargetsForCall(SSAPropagationCallGraphBuilder.java:2079)
at
com.ibm.wala.ipa.callgraph.propagation.SSAPropagationCallGraphBuilder$ConstraintVisitor.visitInvokeInternal(SSAPropagationCallGraphBuilder.java:1159)
at
com.ibm.wala.ipa.callgraph.propagation.SSAPropagationCallGraphBuilder$ConstraintVisitor.visitInvoke(SSAPropagationCallGraphBuilder.java:1115)
at
com.ibm.wala.ssa.SSAInvokeInstruction.visit(SSAInvokeInstruction.java:94)
at
com.ibm.wala.ipa.callgraph.propagation.SSAPropagationCallGraphBuilder.addBlockInstructionConstraints(SSAPropagationCallGraphBuilder.java:273)
at
com.ibm.wala.ipa.callgraph.propagation.SSAPropagationCallGraphBuilder.addNodeInstructionConstraints(SSAPropagationCallGraphBuilder.java:250)
at
com.ibm.wala.ipa.callgraph.propagation.SSAPropagationCallGraphBuilder.unconditionallyAddConstraintsFromNode(SSAPropagationCallGraphBuilder.java:226)
at
com.ibm.wala.ipa.callgraph.propagation.SSAPropagationCallGraphBuilder.addConstraintsFromNode(SSAPropagationCallGraphBuilder.java:191)
at
com.ibm.wala.ipa.callgraph.propagation.PropagationCallGraphBuilder.addConstraintsFromNewNodes(PropagationCallGraphBuilder.java:308)
at
com.ibm.wala.ipa.callgraph.propagation.StandardSolver.solve(StandardSolver.java:53)
at
com.ibm.wala.ipa.callgraph.propagation.PropagationCallGraphBuilder.makeCallGraph(PropagationCallGraphBuilder.java:248)

This commit prioritizes a static method over an interface method and
addresses the above problem.

---------

Co-authored-by: Manu Sridharan <msridhar@gmail.com>

core/src/main/java/com/ibm/wala/ipa/callgraph/Entrypoint.java

@@ -70,17 +70,17 @@ public CallSiteReference makeSite(int programCounter) {
       return CallSiteReference.make(
           programCounter, method.getReference(), IInvokeInstruction.Dispatch.SPECIAL);
     } else {
-      if (method.getDeclaringClass().isInterface()) {
+      // It is important to check for static methods before interface methods, since if an interface
+      // contains a static method, it should be called via static dispatch, not interface dispatch
+      if (method.isStatic()) {
+        return CallSiteReference.make(
+            programCounter, method.getReference(), IInvokeInstruction.Dispatch.STATIC);
+      } else if (method.getDeclaringClass().isInterface()) {
         return CallSiteReference.make(
             programCounter, method.getReference(), IInvokeInstruction.Dispatch.INTERFACE);
       } else {
-        if (method.isStatic()) {
-          return CallSiteReference.make(
-              programCounter, method.getReference(), IInvokeInstruction.Dispatch.STATIC);
-        } else {
-          return CallSiteReference.make(
-              programCounter, method.getReference(), IInvokeInstruction.Dispatch.VIRTUAL);
-        }
+        return CallSiteReference.make(
+            programCounter, method.getReference(), IInvokeInstruction.Dispatch.VIRTUAL);
       }
     }
   }

core/src/test/java/com/ibm/wala/core/tests/callGraph/StaticInterfaceMethodTest.java

@@ -0,0 +1,47 @@
+package com.ibm.wala.core.tests.callGraph;
+
+import com.ibm.wala.core.tests.util.TestConstants;
+import com.ibm.wala.ipa.callgraph.AnalysisCacheImpl;
+import com.ibm.wala.ipa.callgraph.AnalysisOptions;
+import com.ibm.wala.ipa.callgraph.AnalysisScope;
+import com.ibm.wala.ipa.callgraph.CallGraph;
+import com.ibm.wala.ipa.callgraph.Entrypoint;
+import com.ibm.wala.ipa.callgraph.impl.DefaultEntrypoint;
+import com.ibm.wala.ipa.cha.ClassHierarchy;
+import com.ibm.wala.ipa.cha.ClassHierarchyException;
+import com.ibm.wala.ipa.cha.ClassHierarchyFactory;
+import com.ibm.wala.types.ClassLoaderReference;
+import com.ibm.wala.types.MethodReference;
+import com.ibm.wala.types.TypeReference;
+import com.ibm.wala.util.CancelException;
+import java.io.IOException;
+import java.util.List;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class StaticInterfaceMethodTest {
+
+  @Test
+  public void staticInterfaceMethodAsEntrypoint()
+      throws ClassHierarchyException, IllegalArgumentException, CancelException, IOException {
+
+    AnalysisScope scope =
+        CallGraphTestUtil.makeJ2SEAnalysisScope(
+            TestConstants.WALA_TESTDATA, CallGraphTestUtil.REGRESSION_EXCLUSIONS);
+    ClassHierarchy cha = ClassHierarchyFactory.make(scope);
+    MethodReference staticInterfaceMethodRef =
+        MethodReference.findOrCreate(
+            TypeReference.findOrCreate(
+                ClassLoaderReference.Application,
+                "LstaticInterfaceMethod/InterfaceWithStaticMethod"),
+            "test",
+            "()V");
+    Iterable<Entrypoint> entrypoints =
+        List.of(new DefaultEntrypoint(staticInterfaceMethodRef, cha));
+    AnalysisOptions options = CallGraphTestUtil.makeAnalysisOptions(scope, entrypoints);
+
+    CallGraph cg = CallGraphTestUtil.buildZeroCFA(options, new AnalysisCacheImpl(), cha, false);
+
+    Assert.assertEquals(1, cg.getNodes(staticInterfaceMethodRef).size());
+  }
+}

core/src/testSubjects/java/staticInterfaceMethod/InterfaceWithStaticMethod.java

@@ -0,0 +1,5 @@
+package staticInterfaceMethod;
+
+public interface InterfaceWithStaticMethod {
+  static void test() {}
+}