I have a problem with sol::function that doesn’t make any sense.

I have this struct that is supposed to hold a sol2 Lua callback function that gets called from C++:

struct CustomBehaviour {
    CustomBehaviour() = default;
    CustomBehaviour(const CustomBehaviour &oth) {
        m_on_update = oth.m_on_update;
    }
    CustomBehaviour &operator=(const CustomBehaviour &oth) {
        m_on_update = oth.m_on_update;
        return *this;
    }

    void set_on_update(sol::function func) {
        assert(func && "not a valid callback");
        m_on_update = std::make_shared<sol::function>(std::move(func));
        std::cout << "set_on_update called, m_on_update setn";
    }

    void call_on_update() const { 
        if(m_on_update) {
            try {
                std::cout << "m_on_update is valid, calling it...n";
                m_on_update->call();
            } catch (const sol::error& e) {
                std::cerr << "Error in CustomBehaviour::on_update lua function: " << e.what() << "n;
            }
        } else {
            std::cout << "m_on_update is not set.n";
        }
    }
    
private:
    std::shared_ptr<sol::function> m_on_update;
};

I won’t share the C++ code that calls that function because it has been tested to work.

Whenever the call_on_update() gets called in C++ it outputs that the function doesn’t exist but if I call that same call_on_update() function to Lua, it magically exist again and works without problems.

Like this:

local behaviour = spawner_ent:add_component_CustomBehaviour()
behaviour:set_on_update(function()
    print("custom behaviour updated")
end)
behaviour:call_on_update()

So basically the sol::function only exists in Lua but not in C++.

I have tried:

• calling the function in C++ every way I can come up with,
• storing the functions in many different ways like C++ lambdas, normal stack variables, smart pointers etc.