RFR 9 and 8u: JDK-8029674: (reflect) getMethods returns default methods that are not members of the class

[Joel Borggrén-Franck]

Hi Joe,

I’ll add a comment.

cheers
/Joel

On 10 jun 2014, at 01:09, Joe Darcy <joe.darcy at oracle.com> wrote:

> Thanks for the investigation Andrej.
> 
> In any case, I'd prefer a comment noting the interned-ness (or mostly interned-ness, etc.) of the name to let other readers of the code using == rather than .equals is intentional and not a bug.
> 
> Thanks,
> 
> -Joe
> 
> On 06/09/2014 12:56 PM, Andrej Golovnin wrote:
>> Hi Joel,
>> 
>>> IIRC name isn’t actually interned with String.intern() but in the VM:s Symbol table as a name representing a (Java) method. Should be equivalent, as long as we don’t start comparing it with == with interned Strings.
>> I think that's not true.
>> 
>> The following small test program prints true on the console:
>> 
>> public class Test {
>> 
>>     public static void main(String... argv) throws Exception {
>>         Method m = Test.class.getMethod("main", String[].class);
>>         System.out.println(m.getName() == new String("main").intern());
>>     }
>> 
>> }
>> 
>> And if you look into reflection.cpp at lines 787-789, you will see following code:
>> 
>>   Symbol*  method_name = method->name();
>>   oop name_oop = StringTable::intern(method_name, CHECK_NULL);
>>   Handle name = Handle(THREAD, name_oop);
>> 
>> And later at the line 798 we have this code:
>> 
>>   java_lang_reflect_Method::set_name(mh(), name());
>> 
>> Therefore I would say the name is actually interned in terms of String.intern().
>> And you can compare the name of a method with == with interned Strings.
>> 
>> The same applies to a name of a class and to a name of a field too.
>> Please feel free to correct me.
>> 
>> Best regards,
>> Andrej Golovnin
>> 
>> 
>>> cheers
>>> /Joel
>>> 
>>> On 07 Jun 2014, at 22:34, Andrej Golovnin <andrej.golovnin at gmail.com> wrote:
>>> 
>>>> Hi Joe,
>>>> 
>>>>> Sorry for the belated review.
>>>>> 
>>>>> Generally the change looks good. One question, in
>>>>> 
>>>>> 2803         private boolean matchesNameAndDescriptor(Method m1, Method m2) {
>>>>> 2804             return m1.getReturnType() == m2.getReturnType() &&
>>>>> 2805                    m1.getName() == m2.getName() &&
>>>>> 2806                    arrayContentsEq(m1.getParameterTypes(),
>>>>> 2807                            m2.getParameterTypes());
>>>>> 2808         }
>>>>> 
>>>>> Should the equality check on 2805 be .equals rather than == ?
>>>>> 
>>>> "==" can be used in this case as the method name is interned by JVM.
>>>> Here is the comment for the field "name" from java.lang.reflect.Method:
>>>> 
>>>>  // This is guaranteed to be interned by the VM in the 1.4
>>>>  // reflection implementation
>>>>  private String              name;
>>>> 
>>>> BTW, in the old version of Class in the line 2766 there was already a similar check:
>>>> 
>>>> 2764                 if (m != null &&
>>>> 2765                     m.getReturnType() == toRemove.getReturnType() &&
>>>> 2766                     m.getName() == toRemove.getName() &&
>>>> 2767                     arrayContentsEq(m.getParameterTypes(),
>>>> 2768                                     toRemove.getParameterTypes())) {
>>>> 2769                     methods[i] = null;
>>>> 
>>>> 
>>>> Best regards,
>>>> Andrej Golovnin
>>>> 
>>>> 
>