[foreign] RFR: Fix UndefinedLayoutException exception message

[Jorn Vernee]

Maurizio Cimadamore schreef op 2019-01-29 15:59:
> Resolving references across interfaces is not expected to work
> reliably. This is the primary reason which sends us towards an
> extraction model that is library-centric, rather than header-centric,
> so that all references in a library should be self-contained.

I've been using a mitigating patch that also scans methods of a Struct 
implementation in LayoutResolver when scanning a struct. Under the 
assumption that a type's layout is defined on that type itself.

> As for your test, it seems like you can get the same exception simply
> by having a single struct interface whose layout has some dandling
> unresolved layout (e.g. an unresolved layout whose layout expression
> is not defined anywhere)?

The tricky part is triggering the resolution of the layout through the 
public API. Trying to allocate a struct will not resolve the struct's 
layout. The only place I found that does this is either the test case 
I've used, where the dangling layout is in a @NativeFunction descriptor, 
or in StructImplGenerator's constructor, which is called when de 
referencing a pointer to a struct.

Of course, I could also just use 
`LayoutResolver.get(Object.class).resolve(Layout.of("${Undefined}"));`. 
Would that be good enough?

Jorn

> Maurizio
> 
> On 28/01/2019 14:52, Jorn Vernee wrote:
>> Ok, it took a while to find a good test case. I was seeing the 
>> exception due to a cross-header layout reference, so that's also the 
>> test case I added. It seems that that is currently the only realistic 
>> use-case where this exception is being thrown. I believe not being 
>> able to resolve cross-header layout references is a known issue as 
>> well?
>> 
>> Updated webrev: 
>> http://cr.openjdk.java.net/~jvernee/panama/webrevs/fixmessage/webrev.01/
>> 
>> Jorn
>> 
>> Jorn Vernee schreef op 2019-01-28 14:16:
>>> Yes, I will do that. (wasn't sure if it was useful enough).
>>> 
>>> Jorn
>>> 
>>> Sundararajan Athijegannathan schreef op 2019-01-28 14:12:
>>>> Is it possible to add a test with invalid (unresolvable) name
>>>> reference in a layout descriptor and check the exception message?
>>>> 
>>>> -Sundar
>>>> 
>>>> On 28/01/19, 6:36 PM, Jorn Vernee wrote:
>>>>> Hi,
>>>>> 
>>>>> JDK-8217245 changed the syntax for Unresolved layouts from 
>>>>> `$(Name)` to `${Name}`. This also means Unresolved now has a 
>>>>> dedicated `layoutExpression` field instead of relying on the name 
>>>>> annotation.
>>>>> 
>>>>> LayoutResolver.UndefinedLayoutException is still using the name 
>>>>> annotation in the exception message, which is now incorrect. This 
>>>>> small patch fixes that, and changes it to use 
>>>>> Unresolved::layoutExpression().
>>>>> 
>>>>> Please review.
>>>>> 
>>>>> Webrev: 
>>>>> http://cr.openjdk.java.net/~jvernee/panama/webrevs/fixmessage/webrev.00/ 
>>>>> Cheers,
>>>>> Jorn