Function newuserdata

pub unsafe extern "C" fn newuserdata(
    state: lua_State,
    size: usize,
) -> *mut c_void

This function allocates a new block of memory with the given size, pushes onto the stack a new full userdata with the block address, and returns this address.

Userdata represent C values in Lua. A full userdata represents a block of memory. It is an object (like a table): you must create it, it can have its own metatable, and you can detect when it is being collected. A full userdata is only equal to itself (under raw equality).

When Lua collects a full userdata with a __gc metamethod, Lua calls the metamethod and marks the userdata as finalized. When this userdata is collected again then Lua frees its corresponding memory.