[foreign] RFR Add sizeof method to Struct type

[Henry Jen]

Allocation do the alignment to make sure we get proper address alignment. We don’t need that here as we want to know the actual size.

I am not 100% sure why current implementation add that alignment padding, perhaps to optimize access, but I am not sure if that’s necessary as the C compiler could have done that. We do want to make allocation at right boundary, NativeScope does align that allocation to 8 which we may want to make it dynamic to each allocation.

Cheers,
Henry

> On Jul 26, 2018, at 8:06 AM, Sundararajan Athijegannathan <sundararajan.athijegannathan at oracle.com> wrote:
> 
> Shouldn't this be consistent ScopeImpl.allocateStruct? user would typically allocateStruct and pass then pass ptr and size of that, right?
> 
> -Sundar
> 
> On 26/07/18, 8:26 PM, Henry Jen wrote:
>> I am not sure why we need the Util.alignUp call here, that’s supposed to be used for allocation to arrange address space.
>> 
>> The layout should have proper padding and give the right size as if you call sizeof() in C on the struct.
>> 
>> Otherwise, SystemABI.sizeof(Layout) should give you the right size based on platform.
>> 
>> Cheers,
>> Henry
>> 
>> 
>>> On Jul 26, 2018, at 1:50 AM, Sundararajan Athijegannathan<sundararajan.athijegannathan at oracle.com>  wrote:
>>> 
>>> Please review.
>>> 
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8208284
>>> Webrev: http://cr.openjdk.java.net/~sundar/8208284/webrev.00/
>>> 
>>> Thanks,
>>> -Sundar