RFR (M): JDK-8159262: Walking PackageEntry Export and ModuleEntry Reads Must Occur Only When Neccessary And Wait Until ClassLoader's Aliveness Determined

[David Holmes]

On 22/06/2016 2:21 PM, Mandy Chung wrote:
>
>> On Jun 21, 2016, at 8:43 PM, David Holmes <david.holmes at oracle.com> wrote:
>>
>> On 22/06/2016 1:33 PM, Mandy Chung wrote:
>>> Platform class loader [1] is previously known as the extension class loader.  We have deprivileged several Java SE modules to be defined by the platform class loader instead of the boot loader. They are not granted with all permissions by default. The class spec of ClassLoader has a section [2] to describe the built-in class loaders.
>>
>> Thanks Mandy. I was surprised to see the addition of code to query if the application classloader as we have always had such code:
>>
>> SystemDictionary::java_system_loader()
>>
>> So AFAICS this addition is not needed:
>>
>> 178 // Returns true if the passed class loader is the application class loader.
>> 179 bool SystemDictionary::is_application_class_loader(Handle class_loader) {
>> 180   if (class_loader.is_null()) {
>> 181     return false;
>> 182   }
>> 183   return (class_loader->klass() == SystemDictionary::jdk_internal_loader_ClassLoaders_AppClassLoader_klass());
>> 184 }
>>
>
> This might be better to rename it to is_builtin_application_loader?

Maybe ...

>> But for that matter why do we have SystemDictionary::jdk_internal_loader_ClassLoaders_AppClassLoader_klass and SystemDictionary::java_system_loader ? They are, or should be, the same thing.
>>
>
> In almost all cases except when -Djava.system.class.loader is set to a custom class loader:
>
> java_system_loader may be a custom system class loader which is not an instance of jdk_internal_loader_ClassLoaders_AppClassLoader_klass.

... so we're not really asking if it is the system/application loader 
but if it is a particular type of classloader that is fulfilling that role?

Which then begs the question as to what we are doing that depends on a 
specific type of classloader and what we do if not dealing with such a 
type ??

Thanks,
David

> Mandy
>