#include <iostream>
using namespace std;

#include "lua.hpp"

#define SOL_ALL_SAFETIES_ON 1
#include "sol3.hpp"

int main() {
    sol::state lua;
    lua.open_libraries(sol::lib::base);
    lua.set_function("intBuilder", []() -> shared_ptr<const int> { return make_shared<int>(10); });
    lua.set_function("intReader", [](shared_ptr<const int>& val) { cout << "intReader" << endl;} );
    lua.script(R"(
               print('hello from lua')
               local sharedInt = intBuilder()
               intReader(sharedInt)
               )");
    return 0;
}

hello from lua
[sol2] An error occurred and has been passed to an error handler: sol: runtime error: stack index 1, expected userdata, received sol.sol::d::u<int>: unrecognized userdata (not pushed by sol?) (bad argument into 'void(std::shared_ptr<const int>&)')
stack traceback:
        [C]: in function 'base.intReader'
        [string "..."]:4: in main chunk
terminate called after throwing an instance of 'sol::error'
  what():  sol: runtime error: stack index 1, expected userdata, received sol.sol::d::u<int>: unrecognized userdata (not pushed by sol?) (bad argument into 'void(std::shared_ptr<const int>&)')
stack traceback:
        [C]: in function 'base.intReader'
        [string "..."]:4: in main chunk
Aborted (core dumped)