mirror of
https://github.com/hsoft/collapseos.git
synced 2024-11-08 23:18:04 +11:00
03e529b762
This scheme of "when we handle line-by-line, compile one word at a time then execute" so that we could allow words like "CREATE" to call "readword" before continuing was a bad scheme. It made things like branching outside of a colon definition impossible. This commit implement a new "litWord". When an undefined word is encountered at compile time, it is included as-is in a string literal word. It is at run time that we decide what to do with it.
43 lines
1.1 KiB
NASM
43 lines
1.1 KiB
NASM
; The Parameter stack (PS) is maintained by SP and the Return stack (RS) is
|
|
; maintained by IX. This allows us to generally use push and pop freely because
|
|
; PS is the most frequently used. However, this causes a problem with routine
|
|
; calls: because in Forth, the stack isn't balanced within each call, our return
|
|
; offset, when placed by a CALL, messes everything up. This is one of the
|
|
; reasons why we need stack management routines below. IX always points to RS'
|
|
; Top Of Stack (TOS)
|
|
;
|
|
; This return stack contain "Interpreter pointers", that is a pointer to the
|
|
; address of a word, as seen in a compiled list of words.
|
|
|
|
; Push value HL to RS
|
|
pushRS:
|
|
inc ix
|
|
inc ix
|
|
ld (ix), l
|
|
ld (ix+1), h
|
|
ret
|
|
|
|
; Pop RS' TOS to HL
|
|
popRS:
|
|
ld l, (ix)
|
|
ld h, (ix+1)
|
|
dec ix
|
|
dec ix
|
|
ret
|
|
|
|
; Verifies that SP is within bounds. If it's not, call ABORT
|
|
chkPS:
|
|
ld hl, (INITIAL_SP)
|
|
; We have the return address for this very call on the stack. Let's
|
|
; compensate
|
|
dec hl \ dec hl
|
|
or a ; clear carry
|
|
sbc hl, sp
|
|
ret nc ; (INITIAL_SP) >= SP? good
|
|
; underflow
|
|
ld hl, .msg
|
|
call printstr
|
|
jp abort
|
|
.msg:
|
|
.db "stack underflow", 0
|