RFR(XS) 8191585 VM anonymous classes created during CDS dump time cause crash

[Ioi Lam]

Hi Harold,

Thanks for catching this. I've moved the check into do_cld() as you 
suggested. I also added comments in 
cld::is_{platform,system}_class_loader_data(), similar to the existing 
comments in cld::is_boot_class_loader_data().

http://cr.openjdk.java.net/~iklam/jdk11/8191585-vm-anon-classes-cause-dumping-crash.v02/

Thanks

- Ioi


On 3/6/18 11:45 AM, harold seigel wrote:
> Hi Ioi,
>
> This change will cause ClassLoaderData::is_builtin_class_loader_data() 
> to return false for all anonymous classes except for the boot loader.
>
> Also, other callers of is_builtin_class_loader_data(), such as 
> Klass::class_loader_and_module_name(), probably want that function to 
> return true even for anonymous CLDs.
>
> Instead of changing is_platform_class_loader_data() and 
> is_system_class_loader_data(), could you add a !is_anonymous() check 
> to do_cld() ?
>
> Or, add new is_*_class_loader_data() methods that only return true if 
> the CLD is not anonymous?
>
> Thanks, Harold
>
>
> On 3/6/2018 2:20 PM, Ioi Lam wrote:
>> Hi,
>>
>> Please review this small VM change and the corresponding test case.
>>
>> https://bugs.openjdk.java.net/browse/JDK-8191585
>> http://cr.openjdk.java.net/~iklam/jdk11/8191585-vm-anon-classes-cause-dumping-crash.v01/ 
>>
>>
>> The crash happens in the following code:
>>
>> class CombineDictionariesClosure : public CLDClosure {
>>     void do_cld(ClassLoaderData* cld) {
>>       if (cld->is_system_class_loader_data() || 
>> cld->is_platform_class_loader_data()) {
>>         for (int i = 0; i < cld->dictionary()->table_size(); ++i) {
>>                                  ^^^^^^^^^^^ == NULL
>>
>> The bug is in cld->is_system_class_loader_data() -- the CLD of anon 
>> classes have a NULL
>> cld::dictionary(), but its cld::class_loader() returns the loader 
>> object of the holder
>> class.
>>
>> The fix is to reject if cld::is_anonymous() is true.
>>
>> Thanks
>> - Ioi
>