machine_write_snapshot reads maincpu_regs.pc to record the current
program counter. When called directly from video_canvas_refresh,
maincpu_regs is stale — the CPU loop keeps registers as stack-local
variables and only syncs them to maincpu_regs inside DO_INTERRUPT via
EXPORT_REGISTERS(). The snapshot therefore recorded the wrong PC.
On restore (already trap-based), the wrong PC was faithfully written
back into reg_pc via IMPORT_REGISTERS(), causing the CPU to resume at
a bad address. The game screen looked correct (memory/VIC/SID state
all restored) but the CPU never reached the input-polling code, so
button presses had no effect.
Fix: route machine_write_snapshot through interrupt_maincpu_trigger_trap
so DO_INTERRUPT(IK_TRAP) calls EXPORT_REGISTERS() before the trap
function, capturing the true current PC before the snapshot is written.
ml
