BUG: SystemABI C_LONG and C_LONGLONG are the same

[Maurizio Cimadamore]

On 15/05/2020 02:27, Ty Young wrote:
> The issue with using Constable is that often times the information is 
> the same, so I'm going to end up with not only more garbage but a 
> really huge struct layout for every struct.
Huge in what dimension? Source code? Memory footprint? ... ?
> without creating a ungodly amount of garbage. 

What I'm suggesting is simply something like this:

public static final Optional<GroupLayout> LAYOUT = Optional.of(
             MemoryLayout.ofStruct(
                 MemoryLayouts.C_INT.withAttribute(CROSSPOINT_TYPE, 
NativeInteger.class),
                 MemoryLayout.ofPaddingBits(32)
MemoryLayouts.C_LONGLONG.withAttribute(CROSSPOINT_TYPE, 
NativeLongLong.class),
                 MemoryLayouts.C_INT.withAttribute(CROSSPOINT_TYPE, 
NativeInteger.class),
                 MemoryLayouts.C_INT.withAttribute(CROSSPOINT_TYPE, 
NativeInteger.class),
                 MemoryLayouts.C_INT.withAttribute(CROSSPOINT_TYPE, 
NativeInteger.class),
                 MemoryLayouts.C_INT.withAttribute(CROSSPOINT_TYPE, 
NativeInteger.class),
     ));

Of course, if you find this too verbose (even though I think this is, in 
principle, machine generated code, so maybe that's less of a concern?) - 
you can also define your layout constants off in a separate class:

class CrosspointLayouts {
     MemoryLayout CP_INT = 
MemoryLayouts.C_INT.withAttribute(CROSSPOINT_TYPE, NativeInteger.class);
     MemoryLayout CP_LONGLONG = 
MemoryLayouts.C_LONGLONG.withAttribute(CROSSPOINT_TYPE, 
NativeLongLong.class)

   //rinse and repeat

}

And then your struct simply becomes

public static final Optional<GroupLayout> LAYOUT = Optional.of(
             MemoryLayout.ofStruct(
                 CP_INT,
                 MemoryLayout.ofPaddingBits(32)
                 CP_LONGLONG,
                 CP_INT,
                 CP_INT,
                 CP_INT,
                 CP_INT
     ));

What's wrong with this? Note that with this strategy you actually 
embedded useful, domain-specific info into layouts. Assuming you always 
use the layouts defined in your set of constants, you can always ask 
questions like "what's the carrier for this layout?".

But I don't see the need for burdening the more general abi support with 
this use case.

Maurizio