RFR: 8214363: HeapWord should not be a fake class

[coleen.phillimore at oracle.com]

This is nice but what does this mean?

http://cr.openjdk.java.net/~kbarrett/8214363/open.02/src/hotspot/share/gc/shared/spaceDecorator.cpp.udiff.html

+ return badHeapWord == (max_juint & reinterpret_cast<uintptr_t>(*q));


I thought since it has no implementation class, you can't use *q ?

http://cr.openjdk.java.net/~kbarrett/8214363/open.02/src/hotspot/share/gc/shared/vmStructs_gc.hpp.udiff.html

Checked SA, looks unused. Phew.

thanks,
Coleen

On 2/14/19 5:54 PM, Kim Barrett wrote:
> I meant to send this to hotspot-dev, not hotspot-runtime-dev.  Please use the other thread.
>
>> On Feb 14, 2019, at 5:04 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
>>
>> Please review this change to the definitions of HeapWord and MetaWord.
>> They are no longer a class type.  Rather, they are typedefs for a
>> pointer to associated incomplete (and never defined) helper classes.
>> Thus, we no longer pretend to have class objects where they never
>> existed.
>>
>> Among other things, this makes memset on a HeapWord[] no longer trigger
>> gcc8's new -Wclass-memaccess in ObjectStartArray::set_covered_region().
>>
>> Other than the change to the definitions of HeapWord and MetaWord,
>> most of the changes are removal of no longer valid forward class
>> declarations for those types.
>>
>> CR:
>> https://bugs.openjdk.java.net/browse/JDK-8214363
>>
>> Webrev:
>> http://cr.openjdk.java.net/~kbarrett/8214363/open.02/
>>
>> Testing:
>> mach5 tier1-3.
>