Support generating locals that reference generated class types (#146)

kkoser · kkoser · commit 53339f914a99 · 2019-11-27T10:54:33.000-08:00
We have had support for the const-class operation, but it was only possible to
fill a local with the value of a Class object you could reference in the geneeration
context. This meant that it was not possible to generate a reference to a generated
class, as it did not exist in the class loader until after the generation was finished
and the new class loader could be used.

The real issue here is the restriction of the loadConstant() method, which requires an
actual Class object. This class object gets turned into a string internally for code
generation, and so we don't actually need a real class to fill the variable value
correctly. Using a TypeId will still get converted to a ConstantInsn under the hood,
and the value will be assigned correctly.
diff --git a/dexmaker-tests/src/androidTest/java/com/android/dx/DexMakerTest.java b/dexmaker-tests/src/androidTest/java/com/android/dx/DexMakerTest.java
@@ -171,6 +171,26 @@ public void testInvokeStatic() throws Exception {
         assertEquals(10, getMethod().invoke(null, 4));
     }
 
+    @Test
+    public void testLoadDeferredClassConstant() throws Exception {
+        /*
+         * public static String call() {
+         *   Class clazz = Generated.class;
+         *   return clazz.getSimpleName();
+         * }
+         */
+        MethodId<?, String> methodId = GENERATED.getMethod(TypeId.STRING, "call");
+        Code code = dexMaker.declare(methodId, PUBLIC | STATIC);
+        Local<Class> clazz = code.newLocal(TypeId.get(Class.class));
+        Local<String> retValue = code.newLocal(TypeId.STRING);
+        code.loadDeferredClassConstant(clazz, GENERATED);
+        MethodId<Class, String> getSimpleName = TypeId.get(Class.class).getMethod(TypeId.STRING, "getSimpleName");
+        code.invokeVirtual(getSimpleName, retValue, clazz);
+        code.returnValue(retValue);
+
+        assertEquals("Generated", getMethod().invoke(null));
+    }
+
     @Test
     public void testCreateLocalMethodAsNull() throws Exception {
         /*
diff --git a/dexmaker/src/main/java/com/android/dx/Code.java b/dexmaker/src/main/java/com/android/dx/Code.java
@@ -476,15 +476,27 @@ private void splitCurrentLabel(Label alternateSuccessor, List<Label> catchLabels
      * must be a primitive, String, Class, TypeId, or null.
      */
     public <T> void loadConstant(Local<T> target, T value) {
+        loadConstantInternal(target, value);
+    }
+
+    /**
+     * Copies a class type in {@code target}. The benefit to using this method vs {@link Code#loadConstant(Local, Object)}
+     * is that the {@value} can itself be a generated type - {@link TypeId} allows for deferred referencing of class types.
+     */
+    public void loadDeferredClassConstant(Local<Class> target, TypeId value) {
+        loadConstantInternal(target, value);
+    }
+
+    private void loadConstantInternal(Local target, Object value) {
         Rop rop = value == null
-                ? Rops.CONST_OBJECT_NOTHROW
-                : Rops.opConst(target.type.ropType);
+                  ? Rops.CONST_OBJECT_NOTHROW
+                  : Rops.opConst(target.type.ropType);
         if (rop.getBranchingness() == BRANCH_NONE) {
             addInstruction(new PlainCstInsn(rop, sourcePosition, target.spec(),
-                    RegisterSpecList.EMPTY, Constants.getConstant(value)));
+                                            RegisterSpecList.EMPTY, Constants.getConstant(value)));
         } else {
             addInstruction(new ThrowingCstInsn(rop, sourcePosition,
-                    RegisterSpecList.EMPTY, catches, Constants.getConstant(value)));
+                                               RegisterSpecList.EMPTY, catches, Constants.getConstant(value)));
             moveResult(target, true);
         }
     }
