[foreign] RFR 8220063: Generate LayouType constants as part of jextract output

[Jorn Vernee]

Maurizio Cimadamore schreef op 2019-03-05 17:06:
> On top of my head, this looks something more for the Ext code factory
> than for the main one.

But the Ext code factory is for generating the static forwarder. I added 
it to AsmCodeFactory since the changes affect the classes in the regular 
(non-"_h") classes.

If you think this feels more like an extension, maybe we should try to 
figure out some extension/plugin framework first, and then implement 
this feature on top of that (would be a good test case).

> Also, not clear about the changes in LayoutType.ofFunction... there's
> no inference going on whatsoever, in fact your patch does this
> 
> +        return LayoutTypeImpl.ofCallback(Address.ofFunction(64,
> Util.functionof(funcIntf)), References.ofFunction, funcIntf);
> 
> Yes, we discussed about changing @NativeCallback while back, but I'm
> not 100% sure that's the direction we should go, and I'd like not to
> couple things to it.

Instead of the Address layout being passed in, the Function layout is 
extracted from the @NativeCallback annotation. That's what I mean by 
"infer that from the @NativeCallback".

I'm not sure what you mean about changing @NativeCallback? This change 
relies on the current implementation.

Jorn

> Maurizio
> On 05/03/2019 15:41, Jorn Vernee wrote:
> 
>> Hi,
>> 
>> I'd like to contribute a patch which let's jextract generate
>> LayoutType constants in typedef annotation classes, and struct
>> classes for the underlying type. The LayoutType constant has the
>> name of the typedef or struct with an "_t" suffix.
>> 
>> This is useful because;
>> 
>> 1.) No need to manually declare a static final LayoutType if you
>> don't want to call LayoutType.ofStruct(...) everywhere.
>> 
>> 2.) If an API uses a type in it's documentation/tutorials, but that
>> type comes from a typedef, in the generated Jextract bindings you
>> will just find the typedef annotation with that name. But, if we add
>> a LayoutType constant to the typedef annotation class, the user has
>> an easy way to find the underlying type as well. (Very useful with
>> APIs that use typedefs for pretty much anything. Like the Windows
>> API).
>> 
>> I might be a little biased towards this, but I've found that
>> declaring static final LayoutType constants is a must have in
>> non-trivial projects. Both to reduce verbosity and to show the name
>> of the API type in the code, not just the name of the underlying
>> type. e.g. `scope.allocate(MyType_t)` vs.
>> `scope.allocate(DOUBLE.array(2))`.
>> 
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8220063
>> Webrev:
>> 
> http://cr.openjdk.java.net/~jvernee/panama/webrevs/8220063/webrev.00/
>> 
>> 
>> I did 3 other things to implement this:
>> 
>> 1.) Drop Address parameter of LayoutType.ofFunction, since we can
>> just infer that from the @NativeCallback annotation instead.
>> 2.) Fixed issue where a typedef of a function type was not
>> generating an @NativeCallback class.
>> 3.) Sharpened typing in TypeDictionary and JType w.r.t.
>> JType.FunctionalInterfaceType.
>> 
>> Thanks,
>> Jorn