commit 1268b742c8cff7318dc0b5b283cbaeabfe0725ba
author Narayan Kamath <narayan@google.com> Fri Jul 11 19:15:11 2014 +0100
committer Narayan Kamath <narayan@google.com> Fri Aug 01 14:53:30 2014 +0100
tree 62ccc7504d91617154c6474b933562cc70255fce
parent 89c210bf418a152ccabfbbf853ddcce33aea450d

Fix broken JNI IsAssignableFrom.

The expected argument order was the opposite of what the spec
dictated.

Reported-By: Mikhail Naganov <mnaganov@google.com>
bug: 16531674

Change-Id: I1ebc6d5814ebb4feeb96f3ecdf1a4602da4ba7ce

runtime/jni_internal.cc

diff --git a/runtime/jni_internal.cc b/runtime/jni_internal.cc
index d5b90f2..43b9912 100644
--- a/runtime/jni_internal.cc
+++ b/runtime/jni_internal.cc
@@ -677,13 +677,15 @@
     return soa.AddLocalReference<jclass>(c->GetSuperClass());
   }
 
+  // Note: java_class1 should be safely castable to java_class2, and
+  // not the other way around.
   static jboolean IsAssignableFrom(JNIEnv* env, jclass java_class1, jclass java_class2) {
     CHECK_NON_NULL_ARGUMENT_RETURN(java_class1, JNI_FALSE);
     CHECK_NON_NULL_ARGUMENT_RETURN(java_class2, JNI_FALSE);
     ScopedObjectAccess soa(env);
     mirror::Class* c1 = soa.Decode<mirror::Class*>(java_class1);
     mirror::Class* c2 = soa.Decode<mirror::Class*>(java_class2);
-    return c1->IsAssignableFrom(c2) ? JNI_TRUE : JNI_FALSE;
+    return c2->IsAssignableFrom(c1) ? JNI_TRUE : JNI_FALSE;
   }
 
   static jboolean IsInstanceOf(JNIEnv* env, jobject jobj, jclass java_class) {

runtime/jni_internal_test.cc

diff --git a/runtime/jni_internal_test.cc b/runtime/jni_internal_test.cc
index 7c7e60c..da3080f 100644
--- a/runtime/jni_internal_test.cc
+++ b/runtime/jni_internal_test.cc
@@ -950,8 +950,28 @@
   jclass string_class = env_->FindClass("java/lang/String");
   ASSERT_NE(string_class, nullptr);
 
-  ASSERT_TRUE(env_->IsAssignableFrom(object_class, string_class));
-  ASSERT_FALSE(env_->IsAssignableFrom(string_class, object_class));
+  // A superclass is assignable from an instance of its
+  // subclass but not vice versa.
+  ASSERT_TRUE(env_->IsAssignableFrom(string_class, object_class));
+  ASSERT_FALSE(env_->IsAssignableFrom(object_class, string_class));
+
+  jclass charsequence_interface = env_->FindClass("java/lang/CharSequence");
+  ASSERT_NE(charsequence_interface, nullptr);
+
+  // An interface is assignable from an instance of an implementing
+  // class but not vice versa.
+  ASSERT_TRUE(env_->IsAssignableFrom(string_class, charsequence_interface));
+  ASSERT_FALSE(env_->IsAssignableFrom(charsequence_interface, string_class));
+
+  // Check that arrays are covariant.
+  jclass string_array_class = env_->FindClass("[Ljava/lang/String;");
+  ASSERT_NE(string_array_class, nullptr);
+  jclass object_array_class = env_->FindClass("[Ljava/lang/Object;");
+  ASSERT_NE(object_array_class, nullptr);
+  ASSERT_TRUE(env_->IsAssignableFrom(string_array_class, object_array_class));
+  ASSERT_FALSE(env_->IsAssignableFrom(object_array_class, string_array_class));
+
+  // Primitive types are tested in 004-JniTest.
 
   // Null as either class should fail.
   CheckJniAbortCatcher jni_abort_catcher;