Member variable access in a C++ Zephyr RTOS Thread

Question

Let me start by mentioning that I'm aware that my solution is neither thread safe nor clean at all... but that's why I'm writing this question:

I'm trying to implement a thread in a C++ class in Zephyr that can access a member variable. However, this is more of a general C++ question.

Here's my working solution:

• stepper.h

class Stepper
{
...
private:
    double speed;

    struct k_thread stepper_thread;

    /* Stepper thread entry */
    static void stepper_thread_entry(void *, void *, void *);

    /* Stepper thread function */
    void stepper_thread_function(auto& desired_speed);
};

• stepper.cpp

Stepper::Stepper(void) : speed(0)
{
k_tid_t stepper_thread_tid = k_thread_create(&stepper_thread,    
                                  stepper_thread_stack_area,
                                  K_THREAD_STACK_SIZEOF(stepper_thread_stack_area),                                
                                  Stepper::stepper_thread_entry, 
                                  this, NULL, NULL,
                                  STEPPER_THREAD_PRIORITY, 0, K_MSEC(10));

}

...

void Stepper::stepper_thread_entry(void *instance, void *, void *)
{
    auto thead_instance = reinterpret_cast<Stepper *>(instance);
    thead_instance->stepper_thread_function(thead_instance->speed);
}

void Stepper::stepper_thread_function(double& desired_speed)
{
    // access desired_speed
    ...
}

I'm not especially happy with the implementation in Stepper::stepper_thread_entry, but it was the only way i found to work around the fact that the K_THREAD_STACK_SIZEOF macro requires a static function.

Is there a cleaner way to implement this?

Thanks in advance :)

edit: fixed formatting erros