[foreign-memaccess] RFR 8226526: Add extra static checks to MemoryAccessVarHandles

[Jorn Vernee]

On 2019-06-21 10:58, Maurizio Cimadamore wrote:
> I realized that there is an issue in the way we construct indexed
> access VH with the combinator - that is, we should _prepend_ the new
> stride to the existing list, not append it.

Good catch, thanks!

> In other words, you want the access coordinates of the final var
> handle to affect the outermost sequence first, then the next enclosed
> sequence, and so forth.
> 
> I've also added a test that checks this.
> 
> http://cr.openjdk.java.net/~mcimadamore/panama/8226526_v2/
> 
> (the patch has been rebased on top of 8226519, so it might not apply
> cleanly on a vanilla repo)

FWIW, having multiple different accessors in JLIAccess was one of the 
reasons I ended putting MemoryAccessVarHandles in java.lang.invoke.

Patch looks good. Minor nits:

- In MemoryAccessVarHandles in a bunch of places in the javadoc; "a 
memory access memory access" -> "Creates a memory access var handle"
- Maybe dereferenceVarHandle should be renamed to dereferenceHandle to 
be more in line with the other names?

Also, I'm wondering if there needs to be a public method for getting the 
default alignment as well. If someone just wants to change the byte 
order, a readable way of getting the default alignment would be nice, 
just like we have ByteOrder.nativeOrder().

Jorn

> Maurizio
> 
> On 20/06/2019 17:50, Maurizio Cimadamore wrote:
>> Hi,
>> as discussed in [1], here's a patch which adds extra checks to the 
>> combinator methods in MemoryAccessVarHandles.
>> 
>> This also consolidates the combinators API, by removing the alignment 
>> and byte order combinators (which are now part of the leaf combinator 
>> method).
>> 
>> I also moved MemoryAccessVarHandle from j.l.invoke to java.foreign - 
>> we want to keep the foreign classes close together in preparation for 
>> when we'll need to push them onto a different (incubating) module.
>> 
>> Webrev:
>> 
>> http://cr.openjdk.java.net/~mcimadamore/panama/8226526/
>> 
>> Cheers
>> Maurizio
>>