downcalls, fixed-sized ABI types

[Michael Zucchi]

On 20/1/20 7:50 pm, Ty Young wrote:
> ABI can be ignored if you want. ABI/ValueLayouts APIs were created to 
> work around all the hard-coded byte sizes which could (potentially) 
> cause bugs[1]. 

No it can't, at least on the foreign-abi branch.

If you try using the sized types (the MemoryTypes.*, not 
MemoryTypes.SysV.*) then SystemABI.downcallHandle() will throw an 
exception because they're missing a required annotation.  As 'attached' 
below.

Anyway Maurizio's response makes it clear it's still work in progress.

Cheers,
  Michael


This works:

                 memcpy = abi.downcallHandle(lib.lookup("memcpy"),     
                             MethodType.methodType(void.class, new 
Class[] {                                         MemoryAddress.class, 
                                         MemoryAddress.class,         
                                 long.class,                             
         }),

                                 FunctionDescriptor.ofVoid(false,     
                                           MemoryLayouts.SysV.C_POINTER, 
                                               
MemoryLayouts.SysV.C_POINTER,                                         
       MemoryLayouts.SysV.C_LONG));


This:
                 memcpy = abi.downcallHandle(lib.lookup("memcpy"),
                                 MethodType.methodType(void.class, new 
Class[] {
                                         MemoryAddress.class,
                                         MemoryAddress.class,
                                         long.class,
                                     }),
                                 FunctionDescriptor.ofVoid(false,
MemoryLayouts.SysV.C_POINTER,
MemoryLayouts.SysV.C_POINTER,
MemoryLayouts.BITS_64_LE));

Will throw:
Caused by: java.lang.IllegalStateException: Unexpected value layout: 
could not determine ABI class
         at 
jdk.incubator.foreign/jdk.internal.foreign.abi.x64.sysv.CallArranger.classifyValueType(CallArranger.java:467)
         at 
jdk.incubator.foreign/jdk.internal.foreign.abi.x64.sysv.CallArranger.classifyType(CallArranger.java:639)
         at 
jdk.incubator.foreign/jdk.internal.foreign.abi.x64.sysv.CallArranger.classifyLayout(CallArranger.java:654)
         at 
jdk.incubator.foreign/jdk.internal.foreign.abi.x64.sysv.CallArranger$UnboxBindingCalculator.getBindings(CallArranger.java:350)
         at 
jdk.incubator.foreign/jdk.internal.foreign.abi.x64.sysv.CallArranger.arrangeDowncall(CallArranger.java:126)
         at 
jdk.incubator.foreign/jdk.internal.foreign.abi.x64.sysv.SysVx64ABI.downcallHandle(SysVx64ABI.java:72)