8212117: Class.forName may return a reference to a loaded but not linked Class

Reviewed-by: dholmes, mchung

src/java.base/share/classes/java/lang/Class.java

@@ -392,6 +392,10 @@ public final class Class<T> implements java.io.Serializable,
      *
      * @see       java.lang.Class#forName(String)
      * @see       java.lang.ClassLoader
+     *
+     * @jls 12.2 Loading of Classes and Interfaces
+     * @jls 12.3 Linking of Classes and Interfaces
+     * @jls 12.4 Initialization of Classes and Interfaces
      * @since     1.2
      */
     @CallerSensitive
@@ -438,6 +442,10 @@ public final class Class<T> implements java.io.Serializable,
      * <p> This method does not check whether the requested class is
      * accessible to its caller. </p>
      *
+     * <p> Note that this method throws errors related to loading and linking as
+     * specified in Sections 12.2 and 12.3 of <em>The Java Language
+     * Specification</em>.
+     *
      * @apiNote
      * This method returns {@code null} on failure rather than
      * throwing a {@link ClassNotFoundException}, as is done by
@@ -465,6 +473,8 @@ public final class Class<T> implements java.io.Serializable,
      *         in a module.</li>
      *         </ul>
      *
+     * @jls 12.2 Loading of Classes and Interfaces
+     * @jls 12.3 Linking of Classes and Interfaces
      * @since 9
      * @spec JPMS
      */
@@ -488,13 +498,21 @@ public final class Class<T> implements java.io.Serializable,
             cl = module.getClassLoader();
         }
 
+        Class<?> ret;
         if (cl != null) {
-            return cl.loadClass(module, name);
+            ret = cl.loadClass(module, name);
         } else {
-            return BootLoader.loadClass(module, name);
+            ret = BootLoader.loadClass(module, name);
         }
+        if (ret != null) {
+            // The loaded class should also be linked
+            linkClass(ret);
+        }
+        return ret;
     }
 
+    private static native void linkClass(Class<?> c);
+
     /**
      * Creates a new instance of the class represented by this {@code Class}
      * object.  The class is instantiated as if by a {@code new}

src/java.base/share/classes/java/lang/invoke/MethodHandles.java

@@ -1927,12 +1927,17 @@ assertEquals("[x, y, z]", pb.command().toString());
         }
 
         /**
-         * Looks up a class by name from the lookup context defined by this {@code Lookup} object. The static
+         * Looks up a class by name from the lookup context defined by this {@code Lookup} object.
+         * This method attempts to locate, load, and link the class, and then determines whether
+         * the class is accessible to this {@code Lookup} object.  The static
          * initializer of the class is not run.
          * <p>
          * The lookup context here is determined by the {@linkplain #lookupClass() lookup class}, its class
-         * loader, and the {@linkplain #lookupModes() lookup modes}. In particular, the method first attempts to
-         * load the requested class, and then determines whether the class is accessible to this lookup object.
+         * loader, and the {@linkplain #lookupModes() lookup modes}.
+         * <p>
+         * Note that this method throws errors related to loading and linking as
+         * specified in Sections 12.2 and 12.3 of <em>The Java Language
+         * Specification</em>.
          *
          * @param targetName the fully qualified name of the class to be looked up.
          * @return the requested class.
@@ -1944,6 +1949,9 @@ assertEquals("[x, y, z]", pb.command().toString());
          * modes.
          * @exception SecurityException if a security manager is present and it
          *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
+         *
+         * @jls 12.2 Loading of Classes and Interfaces
+         * @jls 12.3 Linking of Classes and Interfaces
          * @since 9
          */
         public Class<?> findClass(String targetName) throws ClassNotFoundException, IllegalAccessException {

src/java.base/share/classes/sun/launcher/LauncherHelper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2007, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -62,6 +62,7 @@ import java.nio.charset.Charset;
 import java.nio.file.DirectoryStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.security.AccessControlException;
 import java.text.Normalizer;
 import java.text.MessageFormat;
 import java.util.ArrayList;
@@ -724,6 +725,9 @@ public final class LauncherHelper {
         } catch (LinkageError le) {
             abort(null, "java.launcher.module.error3", mainClass, m.getName(),
                     le.getClass().getName() + ": " + le.getLocalizedMessage());
+        } catch (AccessControlException ace) {
+            abort(ace, "java.launcher.module.error5", mainClass, m.getName(),
+                    ace.getClass().getName(), ace.getLocalizedMessage());
         }
         if (c == null) {
             abort(null, "java.launcher.module.error2", mainClass, mainModule);
@@ -780,6 +784,9 @@ public final class LauncherHelper {
         } catch (LinkageError le) {
             abort(le, "java.launcher.cls.error6", cn,
                     le.getClass().getName() + ": " + le.getLocalizedMessage());
+        } catch (AccessControlException ace) {
+            abort(ace, "java.launcher.cls.error7", cn,
+                    ace.getClass().getName(), ace.getLocalizedMessage());
         }
         return mainClass;
     }

src/java.base/share/native/libjava/Class.c

@@ -76,6 +76,7 @@ static JNINativeMethod methods[] = {
     {"getRawTypeAnnotations", "()" BA,      (void *)&JVM_GetClassTypeAnnotations},
     {"getNestHost0",         "()" CLS,      (void *)&JVM_GetNestHost},
     {"getNestMembers0",      "()[" CLS,     (void *)&JVM_GetNestMembers},
+    {"linkClass",            "(" CLS ")V",  (void *)&JVM_LinkClass},
 };
 
 #undef OBJ