8073432: Object.getClass() throws stackless NPE, due to C2 intrinsic

Javac should generate NPE checks using Objects.requireNonNull if -target >= 7

Reviewed-by: jlahoda

langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Symtab.java

@@ -147,6 +147,7 @@ public class Symtab {
     /** Predefined types.
      */
     public final Type objectType;
+    public final Type objectsType;
     public final Type classType;
     public final Type classLoaderType;
     public final Type stringType;
@@ -408,6 +409,7 @@ public class Symtab {
 
         // Enter predefined classes.
         objectType = enterClass("java.lang.Object");
+        objectsType = enterClass("java.util.Objects");
         classType = enterClass("java.lang.Class");
         stringType = enterClass("java.lang.String");
         stringBufferType = enterClass("java.lang.StringBuffer");

langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/Gen.java

@@ -124,6 +124,7 @@ public class Gen extends JCTree.Visitor {
         genCrt = options.isSet(XJCOV);
         debugCode = options.isSet("debugcode");
         allowInvokedynamic = target.hasInvokedynamic() || options.isSet("invokedynamic");
+        allowBetterNullChecks = target.hasObjects();
         pool = new Pool(types);
 
         // ignore cldc because we cannot have both stackmap formats
@@ -150,6 +151,7 @@ public class Gen extends JCTree.Visitor {
     private final boolean genCrt;
     private final boolean debugCode;
     private final boolean allowInvokedynamic;
+    private final boolean allowBetterNullChecks;
 
     /** Default limit of (approximate) size of finalizer to inline.
      *  Zero means always use jsr.  100 or greater means never use
@@ -1983,8 +1985,13 @@ public class Gen extends JCTree.Visitor {
 
     /** Generate a null check from the object value at stack top. */
     private void genNullCheck(DiagnosticPosition pos) {
+        if (allowBetterNullChecks) {
+            callMethod(pos, syms.objectsType, names.requireNonNull,
+                    List.of(syms.objectType), true);
+        } else {
             callMethod(pos, syms.objectType, names.getClass,
                     List.<Type>nil(), false);
+        }
         code.emitop0(pop);
     }
 

langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/Target.java

@@ -121,6 +121,12 @@ public enum Target {
         return compareTo(JDK1_7) >= 0;
     }
 
+    /** Does the target JDK contains the java.util.Objects class?
+     */
+    public boolean hasObjects() {
+        return compareTo(JDK1_7) >= 0;
+    }
+
     /** Does the VM support polymorphic method handle invocation?
      *  Affects the linkage information output to the classfile.
      *  An alias for {@code hasInvokedynamic}, since all the JSR 292 features appear together.

langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/util/Names.java

@@ -171,6 +171,7 @@ public class Names {
     public final Name deprecated;
     public final Name ex;
     public final Name package_info;
+    public final Name requireNonNull;
 
     //lambda-related
     public final Name lambda;
@@ -307,6 +308,7 @@ public class Names {
         deprecated = fromString("deprecated");
         ex = fromString("ex");
         package_info = fromString("package-info");
+        requireNonNull = fromString("requireNonNull");
 
         //lambda-related
         lambda = fromString("lambda$");

langtools/test/tools/javac/8074306/TestSyntheticNullChecks.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2015, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8074306
+ * @summary NULLCHK is emitted as Object.getClass
+ * @compile -source 6 -target 6 TestSyntheticNullChecks.java
+ * @run main TestSyntheticNullChecks 6
+ * @clean TestSyntheticNullChecks*
+ * @compile -source 7 -target 7 TestSyntheticNullChecks.java
+ * @run main TestSyntheticNullChecks 7
+ * @clean TestSyntheticNullChecks*
+ * @compile TestSyntheticNullChecks.java
+ * @run main TestSyntheticNullChecks 9
+ */
+public class TestSyntheticNullChecks {
+
+    class Inner { }
+
+    static void generateSyntheticNPE(TestSyntheticNullChecks outer) {
+        outer.new Inner(); //javac will generate a synthetic NPE check for 'outer'
+    }
+
+    public static void main(String[] args) {
+        int version = Integer.valueOf(args[0]);
+        boolean useObjects = version >= 7;
+        try {
+            generateSyntheticNPE(null);
+        } catch (NullPointerException npe) {
+            boolean hasRequireNotNull = false;
+            for (StackTraceElement e : npe.getStackTrace()) {
+                if (e.getClassName().equals("java.util.Objects") &&
+                        e.getMethodName().equals("requireNonNull")) {
+                    hasRequireNotNull = true;
+                    break;
+                }
+            }
+            if (hasRequireNotNull != useObjects) {
+                throw new AssertionError();
+            }
+        }
+    }
+}