; A software interrupt that names a vector with nothing in it, CAUGHT.
;
; That fault used to be the one the machine had no way of handing over, because the thing
; that would hand it over is the thing that has just found nothing to hand it to. It stopped
; the machine, and no program could do anything about it - which made calling a service the
; system does not implement fatal, and that is an ordinary mistake to make.
;
; It goes to a vector of its own now, with the number of the empty entry in Q. This catches
; it, says which one it was, steps over the SWI and its operand, and carries on - so the
; output says both that the fault arrived and that a program can survive it.
;
; Correct output is:
;   empty vector 28
;   carried on
;   and a clean halt.

#Include console.asm

#Program

start:
  SWI 0d40                  ; Forty is 0x28, and nothing is installed there.

  SETD.0 Carried
  CALL printString
  CALL newLine
  HALT

; Entered because there was nowhere to go. Q holds which entry was empty, and it is the only
; thing on this machine a handler is handed in a register.
missing:
  SETD.0 EmptyText
  CALL printString
  MVQA
  CALL printByteHex
  CALL newLine

  ; ---- Carrying on past it ----
  ;
  ; The frame holds the address after the SWI and the byte naming its vector, so a bare RETI
  ; already lands past the instruction that faulted. That is not true of every fault here -
  ; a refused port or a byte that does not decode both resume ON the thing that failed - so
  ; it is worth saying out loud which kind this one is.
  RETI

#Data

EmptyText:
"empty vector "
Carried:
"carried on"

#Vectors

  Boot      start
  NoHandler missing