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cc65/libsrc/common/setjmp.s

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;
; Ullrich von Bassewitz, 06.06.1998
;
; int setjmp (jmp_buf buf);
;
.export __setjmp
.importzp sp, ptr1
__setjmp:
sta ptr1 ; Save buf
stx ptr1+1
ldy #0
; The parameter stack is now empty, put it into buf
lda sp
sta (ptr1),y
iny
lda sp+1
sta (ptr1),y
iny
; Put the return stack pointer next
tsx
inx
inx ; drop return address
txa
sta (ptr1),y
iny
; Last thing is the return address.
pla
tax
pla
sta (ptr1),y ; high byte first
iny
pha
txa
sta (ptr1),y
pha
; Return zero
lda #0
tax
rts