09543: LUA bpset / wpset functions cause MAME crash

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
09543	Plugins	Major	Always	2 days ago	1 day ago

Tester	jman	View Status	Public	Platform	MAME (Official Binary)
Assigned To	cuavas	Resolution	Fixed	OS	Windows (x64)
Status [?]	Resolved			Driver
Version	0.289	Fixed in Version	0.290GIT	Build	x64
		Fixed in Git Commit	6d1bdb5	Github Pull Request #

Summary	09543: LUA bpset / wpset functions cause MAME crash
Description	LUA bpset / wpset functions cause MAME crash after 0.248 or later.
Steps To Reproduce	1) Execute MAME with "mame -debug -plugin console btime" 2) Focus on the LUA console 3) Input "cpu = manager.machine.devices[':maincpu'] 4) Next, input "cpu.debug:bpset(0x1000)" 5) Crash
Additional Information
Github Commit

Flags
Regression Version	0.248
Affected Sets / Systems

Attached Files	luaconsole0.248.png (61,900 bytes) 2 days ago Uploaded by jman LUA crash on the console in 0.248

No.24667 cuavas Administrator 2 days ago	Two things: * You should not use “-plugin console” (use “-console”) * It works if you provide the condition and action, even if they’re empty (e.g. “bpset(0x1000, '', '')”
No.24668 jman Tester 1 day ago	Thanks, it works. I check cheat and gdbstub LUA plug-in as reference. cheat/init.lua local function bpset(cheat, dev, addr, func) ... local idx = dev.debug:bpset(addr) ... end local function wpset(cheat, dev, space, wptype, addr, len, func) ... local idx = dev.debug:wpset(space, wptype, addr, len) ... end gdbstub/init.lua local btype, addr, kind = packet:match("Z([0-4]),(%x+),(.*)") addr = tonumber(addr, 16) if btype == "0" then socket:write("") -- is machine dependant elseif btype == "1" then ... local idx = cpu.debug:bpset(addr) ... elseif btype == "2" then ... local idx = cpu.debug:wpset(cpu.spaces["program"], "w", addr, 1) ... elseif btype == "3" then ... local idx = cpu.debug:wpset(cpu.spaces["program"], "r", addr, 1) ... elseif btype == "4" then ... local idx = cpu.debug:wpset(cpu.spaces["program"], "rw", addr, 1) ... end wpset() and bpset() in these plug-ins don't set "condition" and "action". What kind of magic are you using? For now, you can close this issue.
No.24669 Robbbert Moderator 1 day ago	I was going to confirm this crash, since mame should never crash, no matter what happens. However, you've asked for it to be closed.
No.24670 cuavas Administrator 1 day ago	Well I suspect the gdbstub plugin no longer works. No-one actually uses it (it isn’t the same as using the gdbstub debugger module with “-debugger gdbstub”, which people do use and which does work). It probably worked at some point, but broke due to things changing. At some point, someone changed the action parameter for device_debug::breakpoint_set from const char * to std::string_view without checking all the call sites for the possibility of passing nullptr. Now if something tries passing nullptr, it will result in the crash when trying to determine the length of the string. From a quick scan of the source, the Lua engine is the only thing that could actually get hit by this. The other change is that at some point, sol switched from just passing nullptr to raising an error for a const char * when no argument is supplied with all safety checks on. This means that for debug builds, it doesn’t crash, but it gives an error “error: stack index 3, expected string, received no value:” if you omit the condition and action. As for whether MAME is allowed to crash, yes, it is allowed to crash if you do bad things with Lua script. There’s a trade-off between enabling and adding safety checks and performance. There are more safety checks in debug builds than release builds, so there are some things that give an error in debug builds but crash in release builds. But you can still crash debug builds by doing bad things with Lua script. I can probably make these work with the condition and action omitted, though.
No.24673 Robbbert Moderator 1 day ago	I've reopened it, awaiting your fix. Also, if someone else also stumbles across this problem, they will be able to see that it is known.