[foreign] RFR 8217380: LayoutType::ofStruct should try to resolve Struct layout

[Jorn Vernee]

Ok thanks,

FWIW, I thought it was best to try to do the resolution as early as 
possible to avoid having to do it multiple times later on. We need the 
carrier type (which has the annotations) to do the resolution, and the 
earliest time carrier and layout come together seems to be in 
LayoutType.

The other place where we could try and resolve the layout is in Scope, 
right before the allocation, since that's when resolution is needed. 
After sending the RFR email I have been thinking that we might want to 
have some check there either way to see if the type being allocated is 
actually complete. e.g.:

     if(type.isPartial()) {
         throw new IllegalArgumentException("Can not allocate incomplete 
type: " + type);
     }

However, the `isPartial()` check does not only check if a type is 
incomplete. For instance for a pointer; the Address layout isPartial() 
method is inherited from Value which delegates to it's `content`, if it 
has one, to do the `isPartial()` check [1]. This makes sense if we have 
just a Value, but imho Address should override isPartial() to always 
return `true`, since we can always allocate a pointer (just maybe not 
what it points to).

What do you think?

Jorn

[1] : 
http://hg.openjdk.java.net/panama/dev/file/tip/src/java.base/share/classes/java/foreign/layout/Value.java#l100

Maurizio Cimadamore schreef op 2019-01-21 11:52:
> Hi,
> I've been wanting to solve this in the past, but I stumbled upon the
> fact that we could not always ensure 'eager' resolution when calling
> LayoutType.ofStruct. This is something that eventually should be fixed
> - the situations where such resolution cannot happen are always caused
> by the fact that jextract is generating cross-header symbolic
> references - this is another problem that could be addressed by
> switching to a library-per-extraction approach, where then all
> symbolic references will become self-contained.
> 
> In the meantime, your idea of adding a 'tryResolve' is a good one;
> I'll do some more tests on my side, to make sure that everything is
> ok, and then I'll approve
> 
> Cheers
> Maurizio
> 
> On 19/01/2019 15:16, Jorn Vernee wrote:
>> Hi,
>> 
>> Please review the following patch.
>> 
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8217380
>> Webrev: 
>> http://cr.openjdk.java.net/~jvernee/panama/webrevs/8217380/webrev.00/
>> 
>> Thanks,
>> Jorn