# HG changeset patch
# User goetz
# Date 1593596705 -7200
#      Wed Jul 01 11:45:05 2020 +0200
# Node ID 15bab0b3f7822d5bbc3f7e5064256989a9dcc602
# Parent  d0b86d63c00f7e00362284628af09b0355b6e326
8248476: No helpful NullPointerException message after calling fillInStackTrace
Summary: reported by christoph.dreis@freenet.de
Reviewed-by:

diff --git a/src/java.base/share/classes/java/lang/NullPointerException.java b/src/java.base/share/classes/java/lang/NullPointerException.java
--- a/src/java.base/share/classes/java/lang/NullPointerException.java
+++ b/src/java.base/share/classes/java/lang/NullPointerException.java
@@ -70,6 +70,16 @@
         super(s);
     }
 
+    private transient int numStackTracesFilledIn;
+
+    /**
+     * {@inheritDoc}
+     */
+    public synchronized Throwable fillInStackTrace() {
+        numStackTracesFilledIn++;
+        return super.fillInStackTrace();
+    }
+
     /**
      * Returns the detail message string of this throwable.
      *
@@ -88,7 +98,9 @@
      */
     public String getMessage() {
         String message = super.getMessage();
-        if (message == null) {
+        // If the stack trace was changed the extended NPE algorithm
+        // will compute a wrong message.
+        if (message == null && numStackTracesFilledIn == 1) {
             return getExtendedNPEMessage();
         }
         return message;
diff --git a/test/hotspot/jtreg/runtime/exceptionMsgs/NullPointerException/NullPointerExceptionTest.java b/test/hotspot/jtreg/runtime/exceptionMsgs/NullPointerException/NullPointerExceptionTest.java
--- a/test/hotspot/jtreg/runtime/exceptionMsgs/NullPointerException/NullPointerExceptionTest.java
+++ b/test/hotspot/jtreg/runtime/exceptionMsgs/NullPointerException/NullPointerExceptionTest.java
@@ -28,7 +28,7 @@
  * @summary Test extended NullPointerException message for
  *   classfiles generated with debug information. In this case the name
  *   of the variable containing the array is printed.
- * @bug 8218628
+ * @bug 8218628 8248476
  * @modules java.base/java.lang:open
  *          java.base/jdk.internal.org.objectweb.asm
  * @library /test/lib
@@ -41,7 +41,7 @@
  * @summary Test extended NullPointerException message for class
  *   files generated without debugging information. The message lists
  *   detailed information about the entity that is null.
- * @bug 8218628
+ * @bug 8218628 8248476
  * @modules java.base/java.lang:open
  *          java.base/jdk.internal.org.objectweb.asm
  * @library /test/lib
@@ -1281,8 +1281,76 @@
         String msg = new String("A pointless message");
         Asserts.assertTrue(new NullPointerException(msg).getMessage() == msg);
 
+        // If the stack trace was set by the user, the message should not be
+        // created.
+        // This holds for explicitly crated NPEs, but also for implicilty
+        // thrown ones.
+        System.out.println(new NullPointerException().fillInStackTrace().getMessage());
+        System.out.println(new NullPointerException(msg).fillInStackTrace().getMessage());
+
+        Asserts.assertNull(new NullPointerException().fillInStackTrace().getMessage());
+        Asserts.assertTrue(new NullPointerException(msg).fillInStackTrace().getMessage() == msg);
+
+        NullPointerException ex = new NullPointerException();
+        Throwable t = ex.fillInStackTrace();
+
+        Asserts.assertNull(t.getMessage());
+
+        ex = new NullPointerException(msg);
+        t = ex.fillInStackTrace();
+        Asserts.assertTrue(t.getMessage() == msg);
+
+        F f = null;
+        try {
+            f.i = 17;
+        } catch (NullPointerException e) {
+            checkMessage(e, "f.i = 17;", e.getMessage(),
+                         "Cannot assign field \"i\" because " +
+                         (hasDebugInfo ? "\"f\"" : "\"<local4>\"") + " is null");
+            t = e.fillInStackTrace();
+        }
+        checkMessage(t, "e.fillInStackTrace()", t.getMessage(), null);
+
+        // Make sure a new exception thrown when calling fillInStackTrace()
+        // gets the correct message.
+        ex = null;
+        try {
+            ex.fillInStackTrace();
+        } catch (NullPointerException e) {
+            checkMessage(e, "ex.fillInStackTrace()", e.getMessage(),
+                         "Cannot invoke \"java.lang.NullPointerException.fillInStackTrace()\" because " +
+                         (hasDebugInfo ? "\"ex\"" : "\"<local2>\"") + " is null");
+        }
+
+        // setStackTrace does not affect computing the message.
+        // Message and stack trace won't match, though.
+        F f1 = null;
+        F f2 = null;
+        NullPointerException e1 = null;
+        NullPointerException e2 = null;
+        try {
+            f1.i = 18;
+        } catch (NullPointerException e) {
+            checkMessage(e, "f1.i = 18;", e.getMessage(),
+                         "Cannot assign field \"i\" because " +
+                         (hasDebugInfo ? "\"f1\"" : "\"<local5>\"") + " is null");
+            e1 = e;
+        }
+        try {
+            f2.i = 19;
+        } catch (NullPointerException e) {
+            checkMessage(e, "f2.i = 19;", e.getMessage(),
+                         "Cannot assign field \"i\" because " +
+                         (hasDebugInfo ? "\"f2\"" : "\"<local6>\"") + " is null");
+            e2 = e;
+        }
+        e1.setStackTrace(e2.getStackTrace());
+        checkMessage(e1, "f1.i = 18;", e1.getMessage(),
+                     "Cannot assign field \"i\" because " +
+                     (hasDebugInfo ? "\"f1\"" : "\"<local5>\"") + " is null");
+
         // If created via reflection, the message should not be generated.
-        Exception ex = NullPointerException.class.getDeclaredConstructor().newInstance();
+        ex = NullPointerException.class.getDeclaredConstructor().newInstance();
         Asserts.assertNull(ex.getMessage());
     }