Correct the logic to truncate Stack map in CodeContext.restoreLocalVariables

commons-compiler-tests/src/test/java/org/codehaus/commons/compiler/tests/ReportedBugsTest.java

@@ -30,6 +30,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.io.StringReader;
+import java.lang.reflect.Method;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
@@ -1253,6 +1254,59 @@ class ReportedBugsTest extends CommonsCompilerTestSuite {
         ));
     }
 
+    @Test public void
+    testPullRequest148() throws Exception {
+        ISimpleCompiler s = this.compilerFactory.newSimpleCompiler();
+        s.cook((""
+            + "class MyClass {\n"
+            + "    private boolean b1;\n"
+            + "\n"
+            + "    public MyClass(boolean b1) {\n"
+            + "        this.b1 = b1;\n"
+            + "    }\n"
+            + "\n"
+            + "    public Object func(Object i) {\n"
+            + "        final int value_0;\n"
+            + "        // The bug still exist if the if condition is 'true'.\n"
+            + "        // Here we use a variable to make the test more robust,\n"
+            + "        // in case the compiler can eliminate the else branch.\n"
+            + "        if (b1) {\n"
+            + "        } else {\n"
+            + "          int field_0 = 1;\n"
+            + "        }\n"
+            + "        // The second if-else is necessary to trigger the bug.\n"
+            + "        if (b1) {\n"
+            + "        } else {\n"
+            + "          // The bug disappear if it's an int variable.\n"
+            + "          long field_1 = 2;\n"
+            + "        }\n"
+            + "        value_0 = 1;\n"
+            + "\n"
+            + "        // The second final variable is necessary to trigger the bug.\n"
+            + "        final int value_2;\n"
+            + "        if (b1) {\n"
+            + "        } else {\n"
+            + "          int field_2 = 3;\n"
+            + "        }\n"
+            + "        value_2 = 2;\n"
+            + "\n"
+            + "        return null;\n"
+            + "    }\n"
+            + "}\n"
+            + "\n"
+            + "public class JaninoTest {\n"
+            + "    public static Object main() {\n"
+            + "        MyClass c = new MyClass(true);\n"
+            + "        return c.func(null);\n"
+            + "    }\n"
+            + "}\n"
+        ));
+
+        Class clazz = s.getClassLoader().loadClass("JaninoTest");
+        Method m = clazz.getDeclaredMethod("main");
+        Assert.assertNull(m.invoke(null));
+    }
+
     public ClassLoader
     compile(ClassLoader parentClassLoader, CompileUnit... compileUnits) {
 

janino/src/main/java/org/codehaus/janino/CodeContext.java

@@ -228,25 +228,26 @@ class LocalScope {
 
         this.currentLocalScope = scopeToPop.parent;
 
-        // Truncate the stack map.
+        // reuse local variable slots of the popped scope
+        this.nextLocalVariableSlot = scopeToPop.startingLocalVariableSlot;
+
+        // To truncate the stack map, it removes local variables
+        // indicated by the popped scope.
         if (this.currentLocalScope != null) {
             StackMap sm = this.currentInserter.getStackMap();
-            if (sm != null) {
-                int numLocalsInStackMap = 0;
+            if (sm != null && sm.locals().length > 0) {
+                int numActiveSlots = 0;
+                int nextLvIndex = 0;
                 for (VerificationTypeInfo slot : sm.locals()) {
-                    if (slot != StackMapTableAttribute.TOP_VARIABLE_INFO) {
-                        numLocalsInStackMap++;
-                    }
-                }
-                while (numLocalsInStackMap-- > this.allLocalVars.size()) {
-                    sm = sm.popLocal();
+                    if (nextLvIndex >= this.nextLocalVariableSlot) break;
+                    nextLvIndex += slot.category();
+                    numActiveSlots += 1;
                 }
+                int numRemovedSlots = sm.locals().length - numActiveSlots;
+                while (numRemovedSlots-- > 0) sm = sm.popLocal();
                 this.currentInserter.setStackMap(sm);
             }
         }
-
-        // reuse local variable slots of the popped scope
-        this.nextLocalVariableSlot = scopeToPop.startingLocalVariableSlot;
     }
 
     /**