Merge

jdk/src/java.base/share/classes/jdk/internal/misc/Unsafe.java

@@ -1603,11 +1603,50 @@ public final class Unsafe {
         return weakCompareAndSwapShort(o, offset, c2s(expected), c2s(x));
     }
 
+    /**
+     * The JVM converts integral values to boolean values using two
+     * different conventions, byte testing against zero and truncation
+     * to least-significant bit.
+     *
+     * <p>The JNI documents specify that, at least for returning
+     * values from native methods, a Java boolean value is converted
+     * to the value-set 0..1 by first truncating to a byte (0..255 or
+     * maybe -128..127) and then testing against zero. Thus, Java
+     * booleans in non-Java data structures are by convention
+     * represented as 8-bit containers containing either zero (for
+     * false) or any non-zero value (for true).
+     *
+     * <p>Java booleans in the heap are also stored in bytes, but are
+     * strongly normalized to the value-set 0..1 (i.e., they are
+     * truncated to the least-significant bit).
+     *
+     * <p>The main reason for having different conventions for
+     * conversion is performance: Truncation to the least-significant
+     * bit can be usually implemented with fewer (machine)
+     * instructions than byte testing against zero.
+     *
+     * <p>A number of Unsafe methods load boolean values from the heap
+     * as bytes. Unsafe converts those values according to the JNI
+     * rules (i.e, using the "testing against zero" convention). The
+     * method {@code byte2bool} implements that conversion.
+     *
+     * @param b the byte to be converted to boolean
+     * @return the result of the conversion
+     */
     @ForceInline
     private boolean byte2bool(byte b) {
-        return b > 0;
+        return b != 0;
     }
 
+    /**
+     * Convert a boolean value to a byte. The return value is strongly
+     * normalized to the value-set 0..1 (i.e., the value is truncated
+     * to the least-significant bit). See {@link #byte2bool(byte)} for
+     * more details on conversion conventions.
+     *
+     * @param b the boolean to be converted to byte (and then normalized)
+     * @return the result of the conversion
+     */
     @ForceInline
     private byte bool2byte(boolean b) {
         return b ? (byte)1 : (byte)0;

jdk/test/java/lang/instrument/SimpleAgent.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2016, 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.
+ *
+ * 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.
+ */
+
+import java.lang.instrument.Instrumentation;
+
+class SimpleAgent {
+
+    public static void premain(String args, Instrumentation inst) {
+        System.out.println("in premain");
+    }
+
+}

jdk/test/java/lang/instrument/TestAgentWithLimitMods.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2016, 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.
+ *
+ * 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
+ * @summary Tests that the -javaagent option adds the java.instrument into
+ * the module graph
+ * @modules java.instrument
+ * @run shell MakeJAR3.sh SimpleAgent
+ * @run main/othervm -javaagent:SimpleAgent.jar -limitmods java.base TestAgentWithLimitMods
+ *
+ */
+public class TestAgentWithLimitMods {
+
+    public static void main(String[] args) {
+        System.out.println("Test passed");
+    }
+
+}