RFR(S) 8244764 Improve assertion for CPP_VTABLE_PATCH_TYPES_DO

[Ioi Lam]

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



> Thanks,
> Lois