; use to erase the stack to prevent buffer leak side channel attack
stack_clear:

    ; save a, hl, e
    ld (.smc_a), a
    ld (.smc_hl), hl
    ld a, e
    ld (.smc_e), a

    ; set from stackBot + 4 to sp - 1 to 0
    lea de, (ix - 2)
    ld hl, -(stackBot + 3)
    add hl, de
    push hl
    pop bc
    lea hl, (ix - 1)
    ld (hl), 0
    lddr

    ; restore a, hl, e
    ld e, 0
.smc_e:=$-1
    ld a, 0
.smc_a:=$-1
    ld hl, 0
.smc_hl:=$-3
    ld sp, ix
    pop ix
    ret