RFR: JDK-8210252: com/sun/jdi/DebuggerThreadTest.java fails with NPE

[Chris Plummer]

Can you reproduce the problem? If so, maybe to find out which thread is 
a problem you could check for null, print the thread info, and then fail 
the test.

Chris

On 9/4/18 11:14 AM, Gary Adams wrote:
> I'm not sure which thread exited causes the NPE.
> This patch will let  the test continue and at least
> let the list of threads be processed.
>
> The test walks up the parents to the initial thread
> and then "enumerates()" the set of the threads to check.
> There is an inherent race condition in enumerate()
> that recognizes it is a snapshot of a moving target.
>
> On 9/4/18, 1:51 PM, Chris Plummer wrote:
>> Hi Gary,
>>
>> Why has the thread exited if the debuggee is still running?
>>
>> Chris
>>
>> On 9/4/18 5:22 AM, Gary Adams wrote:
>>> Here's a quick fix to avoid the NPE using a getThreadGroup() which 
>>> could be null
>>> if the thread has terminated.
>>>
>>>   Issue: https://bugs.openjdk.java.net/browse/JDK-8210252
>>>
>>> diff --git a/test/jdk/com/sun/jdi/DebuggerThreadTest.java 
>>> b/test/jdk/com/sun/jdi/DebuggerThreadTest.java
>>> --- a/test/jdk/com/sun/jdi/DebuggerThreadTest.java
>>> +++ b/test/jdk/com/sun/jdi/DebuggerThreadTest.java
>>> @@ -77,7 +77,8 @@
>>>          int gotThreads = tg.enumerate(list, true);
>>>          for (int i = 0; i < Math.min(gotThreads, list.length); i++){
>>>              Thread t = list[i];
>>> - String groupName = t.getThreadGroup().getName();
>>> + ThreadGroup tga = t.getThreadGroup();
>>> + String groupName = (tga == null ? "<completed>": tga.getName());
>>>
>>>              System.out.println("Thread [" + i + "] group = '" +
>>>                                 groupName + 
>>
>>
>