RFR (XS) 8185160 -XX:DumpLoadedClassList omits graal classes

[Ioi Lam]

On 10/18/17 6:26 PM, David Holmes wrote:
> Hi Ioi,
>
> On 19/10/2017 9:54 AM, Ioi Lam wrote:
>>
>>
>> On 10/17/17 9:04 PM, David Holmes wrote:
>>> Hi Ioi,
>>>
>>> On 18/10/2017 1:52 PM, Ioi Lam wrote:
>>>> http://cr.openjdk.java.net/~iklam/jdk10/8185160-dump-class-list-omits-graal.v01/ 
>>>>
>>>> https://bugs.openjdk.java.net/browse/JDK-8185160
>>>>
>>>> Summary:
>>>>
>>>> DumpLoadedClassList skips classes that can't be stored into the CDS
>>>> archive. For boot and platform loaders, only classes from the JRT 
>>>> image
>>>> are listed.
>>>>
>>>> The test for "is this class from JRT image" was insufficient. It
>>>> checked only classes whose source ends with "...../modules". For the
>>>> platform loader, which loads the graal classes, the source is in the
>>>> form "jrt:/jdk.internal.vm.compiler".
>>>>
>>>> The fix is to also check for a "jrt:" prefix.
>>>
>>> So ./share/classfile/classLoader.hpp:
>>>
>>> static bool is_jrt(const char* name) { return string_ends_with(name, 
>>> MODULES_IMAGE_NAME); }
>>>
>>> is a badly named function or just plain broken?
>>>
>>
>> I've renamed all the is_jrt() functions to is_modules_image(), so 
>> it's clear as to what it does.
>>
>> See 
>> http://cr.openjdk.java.net/~iklam/jdk10/8185160-dump-class-list-omits-graal.v02/ 
>
>
> Okay. But I'm still a bit confused about the expectations of 
> is_modules_image() - where are these names defined? What does jrt: 
> mean if not "in a module image" ??
>
> That aside your fix does what you needed, so looks fine.
>

The problem we have is the ClassFileParser::source()  returns 
"<JAVA_HOME>/lib/modules" for the boot loader (C code), and 
"jrt:/java.compiler" for the platform loader (Java code). This should 
probably be fixed, but I don't want to deal with that now :-(


>>
>>
>>>> I also restructured the code to make it easier to read -- the 
>>>> nesting of || and && is hard to follow.
>>>>
>>>> The original code had a subtle bug with the "!" operator:
>>>>
>>>> 5938   if (((class_loader == NULL && 
>>>> !ClassLoader::contains_append_entry(stream->source())) ||
>>>> 5939 SystemDictionary::is_platform_class_loader(class_loader)) &&
>>>> 5940       !ClassLoader::is_jrt(stream->source())) {
>>>>
>>>> So if (class_loader == NULL && 
>>>> ClassLoader::contains_append_entry(stream->source()) was true,
>>>> the class would NOT be skipped.
>>>>
>>>> The new version removes the "!".
>>>
>>> So there should be an updated test to trigger the original bug.
>>>
>>
>> I added a test case, but it's in the closed repo for now (since the 
>> test case uses utilities in the closed AppCDS tests). This test will 
>> be opened as part of JDK-8185996
>
> Ok.
>

Thanks
- Ioi

> Thanks,
> David
>
>> Thanks
>> - Ioi
>>
>>> Thanks,
>>> David
>>>
>>>> Thanks
>>>> - Ioi
>>