8342380: Implement JEP 498: Warn upon Use of Memory-Access Methods in sun.misc.Unsafe

Reviewed-by: vklang, jpai

Author: Alan Bateman

src/java.base/share/classes/sun/launcher/resources/launcher.properties

@@ -218,7 +218,7 @@ java.launcher.X.usage=\n\
 \    --sun-misc-unsafe-memory-access=<value>\n\
 \                      allow or deny usage of unsupported API sun.misc.Unsafe\n\
 \                      <value> is one of "allow", "warn", "debug", or "deny".\n\
-\                      The default value is "allow".\n\n\
+\                      The default value is "warn".\n\n\
 These extra options are subject to change without notice.\n
 
 # Translators please note do not translate the options themselves

src/java.base/share/man/java.md

@@ -979,7 +979,7 @@ the Java HotSpot Virtual Machine.
     : Disallow use of the memory-access methods by throwing an
       `UnsupportedOperationException` on every usage.
 
-    The default value when the option is not specified is `allow`.
+    The default value when the option is not specified is `warn`.
 
 
 ## Extra Options for macOS

src/jdk.unsupported/share/classes/sun/misc/Unsafe.java

@@ -1846,7 +1846,7 @@ private enum MemoryAccessOption {
         DENY;
 
         private static MemoryAccessOption defaultValue() {
-            return ALLOW;
+            return WARN;
         }
 
         /**

test/jdk/sun/misc/UnsafeMemoryAccessWarnings.java

@@ -23,7 +23,7 @@
 
 /*
  * @test
- * @bug 8331670
+ * @bug 8331670 8338383
  * @summary Basic test for --sun-misc-unsafe-memory-access=<value>
  * @library /test/lib
  * @compile TryUnsafeMemoryAccess.java
@@ -43,19 +43,15 @@
 class UnsafeMemoryAccessWarnings {
 
     /**
-     * Test default is "allow"
+     * Test default is "warn"
      */
-    @Test
-    void testDefault() throws Exception {
-        test("allocateMemory+freeMemory+objectFieldOffset+putLong+getLong+invokeCleaner")
-            .shouldHaveExitValue(0)
-            .shouldNotContain("WARNING: A terminally deprecated method in sun.misc.Unsafe has been called")
-            .shouldNotContain("WARNING: sun.misc.Unsafe::allocateMemory")
-            .shouldNotContain("WARNING: sun.misc.Unsafe::freeMemory")
-            .shouldNotContain("WARNING: sun.misc.Unsafe::objectFieldOffset")
-            .shouldNotContain("WARNING: sun.misc.Unsafe::putLong")
-            .shouldNotContain("WARNING: sun.misc.Unsafe::getLong")
-            .shouldNotContain("WARNING: sun.misc.Unsafe::invokeCleaner");
+    @ParameterizedTest
+    @ValueSource(strings = {
+            "allocateMemory+freeMemory",
+            "objectFieldOffset+putLong+getLong"
+    })
+    void testDefault(String input) throws Exception {
+        testOneWarning(input);
     }
 
     /**
@@ -81,11 +77,19 @@ void testAllow() throws Exception {
     @ParameterizedTest
     @ValueSource(strings = {
             "allocateMemory+freeMemory",
-            "objectFieldOffset+putLong+getLong",
-            "invokeCleaner"
+            "objectFieldOffset+putLong+getLong"
     })
     void testWarn(String input) throws Exception {
-        var output = test(input, "--sun-misc-unsafe-memory-access=warn").shouldHaveExitValue(0);
+        testOneWarning(input, "--sun-misc-unsafe-memory-access=warn");
+    }
+
+    /**
+     * Test that a warning is printed by the first memory access method only.
+     * @param input comma separated list of Unsafe memory access methods to execute
+     * @param vmopts VM options
+     */
+    private void testOneWarning(String input, String... vmopts) throws Exception {
+        var output = test(input, vmopts).shouldHaveExitValue(0);
 
         // should be warning printed for the first memory access method
         String[] methodNames = input.split("\\+");
@@ -99,6 +103,7 @@ void testWarn(String input) throws Exception {
         int index = 1;
         while (index < methodNames.length) {
             String methodName = methodNames[index++];
+            assertNotEquals(firstMethodName, methodName);
             output.shouldNotContain("WARNING: sun.misc.Unsafe::" + methodName);
         }
     }