Luacontrollers: Crashes when trying to put cdata into `mem`

[TheEt1234]

AsyncErr: Lua: Runtime error from mod 'mesecons_luacontroller' in callback node_on_receive_fields(): /usr/share/luanti/builtin/common/serialize.lua:33: unsupported type: cdata
stack traceback:
	[C]: in function 'error'
	/usr/share/luanti/builtin/common/serialize.lua:33: in function 'count_values'
	/usr/share/luanti/builtin/common/serialize.lua:29: in function 'count_values'
	/usr/share/luanti/builtin/common/serialize.lua:36: in function 'count_objects'
	/usr/share/luanti/builtin/common/serialize.lua:69: in function 'serialize'
	/usr/share/luanti/builtin/common/serialize.lua:225: in function 'serialize'
	.../.minetest/mods/mesecons/mesecons_luacontroller/init.lua:620: in function 'save_memory'
	.../.minetest/mods/mesecons/mesecons_luacontroller/init.lua:677: in function 'run_inner'
	.../.minetest/mods/mesecons/mesecons_luacontroller/init.lua:714: in function 'set_program'
	.../.minetest/mods/mesecons/mesecons_luacontroller/init.lua:806: in function <.../.minetest/mods/mesecons/mesecons_luacontroller/init.lua:797>

should i share how i even got cdata, i mean i think this can be fixed by just checking for it

[TheEt1234]

but i think this is a problem on the minetest side actually, kind of, since that specific cdata object is easily serializable

[TheEt1234]

ok since there are already non-trivial issues, i think i can share how i got cdata inside of a mesecons luacontroller

mem.a = 5ULL

How could this maybe be fixed on the luanti side:

from https://luajit.org/ext_ffi_api.html

Extensions to the Lua Parser

The parser for Lua source code treats numeric literals with the suffixes LL or ULL as signed or unsigned 64 bit integers. Case doesn't matter, but uppercase is recommended for readability. It handles decimal (42LL), hexadecimal (0x2aLL) and binary (0b101010LL) literals.

The imaginary part of complex numbers can be specified by suffixing number literals with i or I, e.g. 12.5i. Caveat: you'll need to use 1i to get an imaginary part with the value one, since i itself still refers to a variable named i.

The only cdata types to my knowledge, that you can use inside luanti, without being a trusted mod, are uint64_t int64_t and complex (those are types from ffi.typeof, if you do type(5ULL) you will get cdata, but if you do ffi.typeof(5ULL) you get ctype<uint_64>)

With their syntax being (number 5 is an example) 5ULL or 5ull (uint_64t) 5LL or 5ull (int64_t) and 5i or 5I (complex)

All of which, when you do tostring() on them, return themselves as ""their syntax"", if that makes sense, so tostring(5ULL) returns the string 5ULL, except complex numbers, those don't support arithmetic but tostring(5i) returns 0+5i, which returns an error when trying to be evaluated

so uhh (i assume core.serialize serializes things into lua code), maybe when serializing cdata, convert it to a string, if the string contains a + character (meaning its a complex number), cut it off leaving only the 5i part

How this could be fixed on mesecons side:

Don't allow cdata in the mem table