ABI specification of interfaces misleading

[fieldvoid]

The spec says "An interface is a pointer to a pointer to a vtbl[]. The vtbl[0] entry is a pointer to the corresponding instance of the object.Interface class." However an interface is actually a vtbl*.

interface A {
  void foo ();
}
interface B {
  void bar ();
}
interface C : A, B {
}
final class D : C {
  void foo () {
  }

  void bar () {
  }
}
void main () {
  C p = new D;
  p.foo;
  p.bar;
}

_Dmain:
0000:   55                       push      RBP
0001:   48 8B EC                 mov       RBP,RSP
0004:   48 83 EC 10              sub       RSP,010h
0008:   E8 00 00 00 00           call      L0
000d:   48 85 C0                 test      RAX,RAX
0010:   74 06                    je        L18
0012:   48 8D 40 10              lea       RAX,010h[RAX]
0016:   EB 02                    jmp short L1a
0018:   31 C0                    xor       EAX,EAX
001a:   48 89 45 F8              mov       -8[RBP],RAX
001e:   48 89 C7                 mov       RDI,RAX
0021:   48 8B 08                 mov       RCX,[RAX]
0024:   48 FF 51 08              call      qword ptr 8[RCX]
0028:   48 83 7D F8 00           cmp       qword ptr -8[RBP],0
002d:   74 0A                    je        L39
002f:   48 8B 55 F8              mov       RDX,-8[RBP]
0033:   48 8D 7A 08              lea       RDI,8[RDX]
0037:   EB 02                    jmp short L3b
0039:   31 FF                    xor       EDI,EDI
003b:   48 83 7D F8 00           cmp       qword ptr -8[RBP],0
0040:   74 0A                    je        L4c
0042:   48 8B 45 F8              mov       RAX,-8[RBP]
0046:   48 8D 48 08              lea       RCX,8[RAX]
004a:   EB 02                    jmp short L4e
004c:   31 C9                    xor       ECX,ECX
004e:   48 8B 11                 mov       RDX,[RCX]
0051:   48 FF 52 08              call      qword ptr 8[RDX]
0055:   31 C0                    xor       EAX,EAX
0057:   C9                       leave
0058:   C3                       ret
main:
0000:   55                       push      RBP
0001:   48 8B EC                 mov       RBP,RSP
0004:   48 8B 15 FC FF FF FF     mov       RDX,[0FFFFFFFCh][RIP]
000b:   E8 00 00 00 00           call      L0
0010:   5D                       pop       RBP
0011:   C3                       ret

The reduced form, or points of interest are:

test      RAX,RAX
...
mov       RCX,[RAX]
...
call      qword ptr 8[RCX]

This is roughly equivalent to:

vtbl* RAX = L0();
vtbl RCX = *RAX;
(RCX + 8)();

[fieldvoid]

"An interface is a pointer to a pointer to a vtbl[]" implies that it is a pointer to another pointer somewhere that holds the address of a vtbl[]. In my opinion, it should really be something like "An interface is a pointer to a vtbl in a vtbl[] where vtbl[0] is the pointer to the instance and the rest of the offsets are interfaces."