RFR(S) 8244764 Improve assertion for CPP_VTABLE_PATCH_TYPES_DO

[Lois Foltan]

On 6/24/2020 2:28 PM, Ioi Lam wrote:
>
>
> On 6/24/20 9:23 AM, Lois Foltan wrote:
>> On 6/23/2020 8:09 PM, Ioi Lam wrote:
>>> https://bugs.openjdk.java.net/browse/JDK-8244764
>>> http://cr.openjdk.java.net/~iklam/jdk16/8244764-CPP_VTABLE_PATCH_TYPES_DO.v01/ 
>>>
>>>
>>> When a new subtype of MetaData is added, CPP_VTABLE_PATCH_TYPES_DO 
>>> must to be
>>> updated. However, there was no assertion check for this. In the 
>>> past, projects
>>> like Valhalla and Loom would get weird crashes with CDS after they 
>>> added new
>>> subclassesof Klass.
>>>
>>> With this patch, you will get a fatal error like this:
>>>
>>> # fatal error: Cannot find C++ vtable for 0x000000080002ec40 -- you
>>>   probably added a new subtype of Klass or MetaData without updating
>>>   CPP_VTABLE_PATCH_TYPES_DO
>>>
>>>
>>> (The code is getting messy. I will clean it up in a subtask:
>>> JDK-8248186 Move CDS C++ vtable code to cppVtables.cpp)
>>>
>>> Thanks
>>> - Ioi
>>
>> Looks good Ioi.  One comment:
>>
>> share/memory/metaspaceShared.cpp:
>> line #977: In the switch statement, MetaspaceObj::MethodDataType will 
>> now be accepted without complaint even though the former comment 
>> stated "should have been removed in removed_unsharable_info"?
>>
>
> Hi Lois, thanks for the review.
>
> Good catch. I've added the ShouldNotReachHere back:
>
>
> diff -r fab75f91cdfb src/hotspot/share/memory/metaspaceShared.cpp
> --- a/src/hotspot/share/memory/metaspaceShared.cpp    Tue Jun 23 
> 17:00:46 2020 -0700
> +++ b/src/hotspot/share/memory/metaspaceShared.cpp    Wed Jun 24 
> 11:26:25 2020 -0700
> @@ -972,6 +972,10 @@
>    case MetaspaceObj::RecordComponentType:
>      // These have no vtables.
>      break;
> +  case MetaspaceObj::MethodDataType:
> +    // We don't archive MethodData <-- should have been removed in 
> removed_unsharable_info
> +    ShouldNotReachHere();
> +    break;
>    default:
>      for (kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
>
> Thanks
> - Ioi
>

Looks good!  Thanks for fixing!
Lois

>
>
>> Thanks,
>> Lois
>