[foreign-jextract] Duplicated interface declarations when using typedefs for function pointers

[Maurizio Cimadamore]

On Thu, 2021-01-28 at 18:57 +0000, Maurizio Cimadamore wrote:
> Filed this:
> 
> https://bugs.openjdk.java.net/browse/JDK-8260602
> 
> Thanks for the report!
> 
> Maurizio

This has been fixed now.

We realized that some of the jextract samples in our document [1] were
also referring to suboptimal functional interface names. We will fix
the document shortly.

Thanks again.

Maurizio

[1] - 
https://github.com/openjdk/panama-foreign/blob/foreign-jextract/doc/panama_jextract.md
> 
> 
> On Thu, 2021-01-28 at 17:57 +0000, Maurizio Cimadamore wrote:
> > This seems odd. But I guess I can see why jextract ends up doing
> > that.
> > 
> > I think what jextract *should* do is to reuse the interface for
> > `callback_t` whenever possible (which should be declared at the
> > toplevel).
> > 
> > In other words, it seems like jextract is re-generating a new
> > interface
> > every time it encounters a reference to a function pointer typedef,
> > which seems a bug.
> > 
> > Maurizio
> > 
> > 
> > 
> > On Thu, 2021-01-28 at 18:48 +0100, Filip Krakowski wrote:
> > > Hi,
> > > 
> > > I just noticed that jextract generates duplicate code
> > > (interfaces)
> > > for 
> > > function pointers within each struct instead at the top-level.
> > > Each interface's name seems to have a suffix based on the
> > > occurrence
> > > of 
> > > the declaration in the source file.
> > > 
> > >     typedef void (*callback_t)(void *arg);
> > > 
> > >     typedef struct first_handler {
> > >          callback_t cb;
> > >     } first_handler_t;
> > > 
> > >     typedef struct second_handler {
> > >          callback_t cb;
> > >     } second_handler_t;
> > > 
> > > This code generates the following java source code.
> > > 
> > >     @C("struct first_handler")public static class first_handler {
> > >     ...
> > >          public static interface cb {
> > > 
> > >                  void apply(jdk.incubator.foreign.MemoryAddress
> > > x0);
> > > 
> > >                  public static  @C("callback_t") MemorySegment
> > >     allocate(cb fi) {
> > >                      return RuntimeHelper.upcallStub(cb.class,
> > > fi,
> > >     ucx_h_constants_0.cb$FUNC(),
> > >     "(Ljdk/incubator/foreign/MemoryAddress;)V");
> > >                  }
> > > 
> > >                  public static  @C("callback_t") MemorySegment
> > >     allocate(cb fi, NativeScope scope) {
> > >                      return allocate(fi).handoff(scope);
> > >                  }
> > >              }
> > >     ...
> > >     }
> > > 
> > >     @C("struct second_handler")public static class second_handler
> > > {
> > >     ...
> > >          public static interface cb$0 {
> > > 
> > >                  void apply(jdk.incubator.foreign.MemoryAddress
> > > x0);
> > > 
> > >                  public static  @C("callback_t") MemorySegment
> > >     allocate(cb$0 fi) {
> > >                      return RuntimeHelper.upcallStub(cb$0.class,
> > > fi,
> > >     ucx_h_constants_0.cb$0$FUNC(),
> > >     "(Ljdk/incubator/foreign/MemoryAddress;)V");
> > >                  }
> > > 
> > >                  public static  @C("callback_t") MemorySegment
> > >     allocate(cb$0 fi, NativeScope scope) {
> > >                      return allocate(fi).handoff(scope);
> > >                  }
> > >              }
> > >     ...
> > >     }
> > > 
> > >  From my point of view both interfaces are identical. Is there a
> > > reason 
> > > for placing them inside the struct class?
> > > 
> > > 
> > > Best regards
> > > Filip
> > > 
> > >