[10] Review Request: 8187442 Xcheck:jni produces various "WARNING in native method" in launcher

[David Holmes]

On 13/09/2017 9:42 AM, Sergey Bylokhov wrote:
> On 9/12/17 16:03, David Holmes wrote:
>> call. That is fine, but still leaves the problem that you are skipping 
>> the DeleteLocalRef call.
> 
> The leak was there before: if we will get an exception at
> "1512 SetByteArrayRegion()"
> then we never call this DeleteLocalRef().
> 
> I assumed it was done intentionally since this will be kind of "fatal" 
> error.

On further checking DeleteLocalRef is not actually needed in 
NewPlatformString at all. The only time it is recommended practice to 
manually delete local refs is when looping, as in NewPlatformStringArray.

So all good - Reviewed. And sorry for the noise.

Thanks,
David



> The same pattern is used in the other places for example in
> NewPlatformStringArray:
> 
>          jstring str = NewPlatformString(env, *strv++);
>          NULL_CHECK0(str);
>          (*env)->SetObjectArrayElement(env, ary, i, str);
>          (*env)->DeleteLocalRef(env, str);
> 
>>
>> Thanks - and sorry again for my confusion on this.
>>
>> David
>> -----
>>
>>>> In addition this does nothing to clear the pending exception so I 
>>>> can not see how it would affect any warnings.
>>>
>>> It does not clear an exception but preserve it instead, and does not 
>>> use the result of the method which produced an exception.
>>>
>>>>
>>>> David
>>>>
>>>>> This value will be propagated to JavaMain() and I as far as 
>>>>> understand will stop the execution.
>>>>>
>>>>>
>>>>> On 9/12/17 13:56, David Holmes wrote:
>>>>>> Hi Sergey,
>>>>>>
>>>>>> On 13/09/2017 5:18 AM, Sergey Bylokhov wrote:
>>>>>>> Hello,
>>>>>>> Please review the fix for jdk10/jdk10.
>>>>>>>
>>>>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8187442
>>>>>>> Webrev can be found at: 
>>>>>>> http://cr.openjdk.java.net/~serb/8187442/webrev.00
>>>>>>
>>>>>> This doesn't look right to me:
>>>>>>
>>>>>>                str = (*env)->CallStaticObjectMethod(env, cls,
>>>>>>                        makePlatformStringMID, USE_STDERR, ary);
>>>>>> +             CHECK_EXCEPTION_RETURN_VALUE(0);
>>>>>>                (*env)->DeleteLocalRef(env, ary);
>>>>>>                return str;
>>>>>>
>>>>>> If there is an exception pending you fail to delete the local ref. 
>>>>>> And there's no need to clear the exception before calling 
>>>>>> DeleteLocalRef as that is okay to call with a pending exception. 
>>>>>> But there is no point returning zero if an exception occurred 
>>>>>> because in that case str will already be 0/NULL.
>>>>>>
>>>>>> The same here:
>>>>>>
>>>>>> 1596     appClass = (*env)->CallStaticObjectMethod(env, cls, mid);
>>>>>> 1597     CHECK_EXCEPTION_RETURN_VALUE(0);
>>>>>> 1598     return appClass;
>>>>>>
>>>>>> If an exception is pending then appClass will be 0/NULL.
>>>>>>
>>>>>> In addition CHECK_EXCEPTION_RETURN_VALUE doesn't clear the pending 
>>>>>> exception so I can't see what warnings this would be clearing up ???
>>>>>>
>>>>>> Thanks,
>>>>>> David
>>>>>> -----
>>>>>>
>>>>>>> The simple application with empty main method produce some 
>>>>>>> "warnings" when Xcheck:jni is used. Because of that it is hard to 
>>>>>>> cleanup other parts of jdk from such warnings.
>>>>>>>
>>>>>>> Two additional checks were added, in both cases the new code will 
>>>>>>> return 0 in the same way as NULL_CHECK0 in the same methods.
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>
>>>
> 
>