[lworld] [Rev 01] RFR: JDK-8243204 add class load time checking of abstract super classes of…

[Frederic Parain]

On Thu, 7 May 2020 15:29:45 GMT, Harold Seigel <hseigel at openjdk.org> wrote:

>> Please review this chagne.  It adds checks of super classes of inline classes.  It checks that an inline class's super
>> class is  either java.lang.Object or an abstract class.  And, if abstract, checks that the super, and its super, etc.
>> do not have instance fields, nor synchronized instance methods, or non-empty constructors, nor constructors with args.
>> The fix was tested with tiers 1 - 3.
>
> Harold Seigel has updated the pull request with a new target base due to a merge or a rebase. The pull request now
> contains three commits:
>  - Merge branch 'lworld' into abstractSuper
>  - JDK-8243204 add class load time checking of abstract super classes of inline type
>  - JDK-8243204 add class load time checking of abstract super classes of inline types

src/hotspot/share/oops/instanceKlass.hpp line 262:

> 261:   bool _invalid_inline_super;   // if true, invalid super type for an inline type.
> 262:   bool _invalid_identity_super; // if true, invalid super type for an identity type.
> 263:

Would it be possible to use two bits from `_misc_flags` instead of adding two bool fields to `InstanceKlass`?

src/hotspot/share/classfile/classFileParser.cpp line 6931:

> 6930:   return false;
> 6931: }
> 6932:

It seems this method could be made static.

src/hotspot/share/classfile/classFileParser.cpp line 6904:

> 6903: // does not implement interface java.lang.IdentityObject (checked elsewhere), has
> 6904: // an empty body-less no-arg constructor, and no synchronized instance methods.
> 6905: bool ClassFileParser::is_invalid_super_for_inline_type(const InstanceKlass* ik) {

The comment should be more explicit about the fact that it is performing a local test, without considering super types.
The final decision taking account super types being performed in `fill_instance_klass()`.

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PR: https://git.openjdk.java.net/valhalla/pull/34