Lunar.h explained: subtable "userdata"

[Procházka Lukáš Ing. - Pontex s. r. o. <LPr@...>]

Hello,

I'm trying to understand Lunar<T> code.

There is still one point I can't understand:

---
    static int push(lua_State *L, T *obj, bool gc=false) {
        if (!obj) { lua_pushnil(L); return 0; }
        luaL_getmetatable(L, T::className);  // lookup metatable in Lua registry
        if (lua_isnil(L, -1)) luaL_error(L, "%s missing metatable", T::className);*/
        int mt = lua_gettop(L);
        subtable(L, mt, "userdata", "v"); // WHY THIS???
...
---

Lunar creates a metatable for each T; that's clear.

(
This metatable has also subtable named "do not trash", which contains keys=userdata for userdata which are to be ignored during GC cycle;
keys in "do not trash" table are weak; obviously.
)

But - why is there a subtable "userdata" with weak values?
It seems to me it is not used anywhere later, so why?

Thanks in advance for any hint or explanation.

Best regards,

Lukas


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Ing. Lukáš Procházka | mailto:LPr@pontex.cz
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