-- Dump the debugger's execution history at a chosen frame.  This gives the actual
-- instruction stream leading into the stuck loop, including call sites -- i.e.
-- which routine called what, which no amount of static reading has told us.
--
--   HIST_FRAME=300 <mame> vt1200 ... -autoboot_script harness/mame/hist.lua

local machine = manager.machine
local dbg = machine.debugger

if not dbg then
	print("ERROR: debugger not enabled; pass -debug")
	machine:exit()
	return
end

local target = tonumber(os.getenv("HIST_FRAME") or "300")
local path   = os.getenv("HIST_OUT")
	or "/home/arti/code/k-space/vt1200/harness/mame/hist.txt"

local n = 0
emu.register_frame_done(function()
	n = n + 1
	if n >= target then
		dbg:command("history " .. path)
		print("history written to " .. path .. " at frame " .. n)
		machine:exit()
	end
end, "vt1200-hist")

dbg.execution_state = 'run'