7170203: TEST_BUG: test/java/nio/MappedByteBuffer/Truncate.java failing intermittently

[Alan Bateman]

A few days we fixed MappedByteBuffer.load so that it that it works even 
after being compiled at runtime:

http://hg.openjdk.java.net/jdk8/tl/jdk/rev/332bebb463d1

It turns out that exposes an issue, of sorts, with one of the tests that 
I did not see before pushing the change. The test truncates a file that 
is mapped and then attempts to read from the mapped buffer, causing the 
thread to terminate with an uncaught Error. The issue is that jtreg runs 
the test in a thread group that has an uncaught exception handler and so 
the uncaught error is causing the test to fail.

There are various ways to fix this, one would be change the task to 
catch Error or Throwable. Another way, which I prefer, is to just set 
the uncaught exception handler on the thread so that we have the 
exception in the test output. Attached is the proposed patch.

-Alan.


diff --git a/test/java/nio/MappedByteBuffer/Truncate.java 
b/test/java/nio/MappedByteBuffer/Truncate.java
--- a/test/java/nio/MappedByteBuffer/Truncate.java
+++ b/test/java/nio/MappedByteBuffer/Truncate.java
@@ -88,6 +88,11 @@
              }
          };
          Thread t = new Thread(r);
+        t.setUncaughtExceptionHandler(new 
Thread.UncaughtExceptionHandler() {
+            public void uncaughtException(Thread t, Throwable e) {
+                e.printStackTrace();
+            }
+        });
          t.start();