C++ 11: Calling a C++ function periodically

I have put together a simple c++ timer class that is supposed to call a given function periodically from various examples on SO as follows:

#include <functional>
#include <chrono>
#include <future>
#include <cstdio>

class CallBackTimer
{
public:
    CallBackTimer()
    :_execute(false)
    {}

    void start(int interval, std::function<void(void)> func)
    {
        _execute = true;
        std::thread([&]()
        {
            while (_execute) {
                func();                   
                std::this_thread::sleep_for(
                std::chrono::milliseconds(interval));
            }
        }).detach();
    }

    void stop()
    {
        _execute = false;
    }

private:
    bool            _execute;
};

Now I want to call this from a C++ class as followsL

class Processor()
{
    void init()
    {
         timer.start(25, std::bind(&Processor::process, this));
    }

    void process()
    {
        std::cout << "Called" << std::endl;
    }
};

However, this calls with the error

terminate called after throwing an instance of 'std::bad_function_call'
what():  bad_function_call