Expose debugger functionality to Lua console

[T045T]

I'd like to drive the MAME debugger externally, and most of what I need is exposed to the Lua console via the emu object already: Memory and hardware introspection, stopping and resuming gameplay.

A few crucial parts are missing though: The ability to single-step, set and remove break- and watchpoints, and to get notified when hitting said points.

Is there a chance to get those, or does something fundamentally make that hard to do?

[cracyc]

I've got a branch with support for break and watch points at https://github.com/cracyc/mame/tree/lua_debugpoint .

[npwoods]

Why not try to build some sort of bridge by which all debugger commands get exposed to LUA?

Granted, there are details that would need to be worked out (commands currently write to the console, and figuring out how to make errors throw LUA exceptions would be non trivial), but that would seem like a better long term solution.

[cracyc]

Okay, I went ahead and did it this way because it requires no changes outside of luaengine. There are three things be aware of here:

1. Break or watch points can only be caught by using emu.register_periodic because it is called when a debugger break occurs.
2. The debugger provides no feedback about which (or if any) break occurred other than the console log. In the emu.register_periodic callback you'll have to read and parse the last line to find out.
3. The none debugger can't be used with the lua console for breakpoints because it will always immediately resume when stopped. Non-interactive scripts should be okay because emu.register_periodic is always called.