path: root/315stack-debug.subx

# The stack shouldn't grow into the code area.

== code

check-stack:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # . save registers
    50/push-eax
    #
    89/<- %eax 4/r32/esp
    81 7/subop/compare %eax 0x01000000/imm32
    {
      7f/jump-if-> break/disp8
      (abort "stack overflow")
    }
$check-stack:end:
    # . restore registers
    58/pop-to-eax
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

show-stack-state:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # . save registers
    50/push-eax
    51/push-ecx
    52/push-edx
    #
    89/<- %edx 4/r32/esp
    # save old cursor position
    (cursor-position 0)  # => eax, ecx
    # print at top-right
    (set-cursor-position 0 0x70 0)
    (draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0 %edx 0xf 0xc)
    # restore cursor position
    (set-cursor-position %eax %ecx)
$show-stack-state:end:
    # . restore registers
    5a/pop-to-edx
    59/pop-to-ecx
    58/pop-to-eax
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

# Helper for debugging deeply recursive calls without logs or traces.
# Turn it on, insert calls in the right places, and you get a terse sense of
# important parts of the call stack. A poor sophont's stack trace.
debug-print:  # x: (addr array byte), fg: int, bg: int    # x is very short; usually a single character
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # . save registers
    50/push-eax
    51/push-ecx
    #
    {
      81 7/subop/compare *Really-debug-print 0/imm32/false
      74/jump-if-= break/disp8
      (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 *(ebp+8) *(ebp+0xc) *(ebp+0x10))
      # clear the screen and continue if we got too close to the bottom
      (cursor-position 0)  # => eax, ecx
      81 7/subop/compare %ecx 0x28/imm32
      75/jump-if-!= break/disp8
      (clear-screen 0)
      (set-cursor-position 0 0 0)
    }
$debug-print:end:
    # . restore registers
    59/pop-to-ecx
    58/pop-to-eax
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

debug-print?:  # -> _/eax: boolean
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    8b/-> *Really-debug-print 0/r32/eax
$debug-print?:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

turn-on-debug-print:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    c7 0/subop/copy *Really-debug-print 1/imm32/true
$turn-on-debug-print:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

turn-off-debug-print:
    # . prologue
    55/push-ebp
    89/<- %ebp 4/r32/esp
    #
    c7 0/subop/copy *Really-debug-print 0/imm32/false
$turn-off-debug-print:end:
    # . epilogue
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return

== data
Really-debug-print:
  0/imm32/false
#?   1/imm32/true