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Appropriate type for non-Rust userdata #672
Description
I'm working with MAME (I have to go through the Lua interface) and I want to make my life a little bit easier when working with MAME values. What's the proper way to represent them?
[MAME]> print(manager)
sol.mame_machine_manager*: 000001f553eba408
[MAME]> print(type(manager))
userdataIs it with AnyUserData?
#[repr(transparent)]
pub struct MameMachineManager(LuaAnyUserData);
Activity
s5bug commentedon Jan 15, 2026
It's definitely not with
LuaAnyUserData: this causes MAME to segfault, despiteLuaValue::type_namereportinguserdata.khvzak commentedon Jan 22, 2026
Do you have a full code?
s5bug commentedon Jan 22, 2026
@khvzak I can't get a minimal reproduction to you for a while (it involves me setting some time aside to write C), but the question in the title is more important. If
LuaAnyUserDatais the wrong type for holding non-Rust userdata, then the problem is with me, not mlua. However, I got the impression from jumping around mlua's source code thatLuaAnyUserDatareally means "any userdata from this same dylib" (which means loading up a mlua library in any environment that adds its own userdata & trying to pass that userdata around should crash).