Error when instantiating custom queue that inherites from std::queue - c++

Question

I have a queue that extends the std::queue
template<typename T, typename Container = std::queue<T>>
class device_queue : public std::queue<T, Container>
{
private:
flag::state state = flag::state::IDLE;
public:
void SetState(const flag::state& _state)
{
state = _state;
}
flag::state GetState() const
{
return state;
}
};
it being declared:
device_queue<Event> cpu_queue;
the usage is just using pop and front, but I keep getting the following error message
/usr/include/c++/9/bits/stl_queue.h: In instantiation of ‘void std::queue<_Tp, _Sequence>::push(const value_type&) [with _Tp = Event; _Sequence = std::queue<Event, std::deque<Event, std::allocator<Event> > >; std::queue<_Tp, _Sequence>::value_type = Event]’:
src/handler.cpp:11:31: required from here
/usr/include/c++/9/bits/stl_queue.h:260:11: error: ‘class std::queue<Event, std::deque<Event, std::allocator<Event> > >’ has no member named ‘push_back’
260 | { c.push_back(__x); }
| ~~^~~~~~~~~
/usr/include/c++/9/bits/stl_queue.h: In instantiation of ‘void std::queue<_Tp, _Sequence>::pop() [with _Tp = Event; _Sequence = std::queue<Event, std::deque<Event, std::allocator<Event> > >]’:
src/handler.cpp:92:23: required from here
/usr/include/c++/9/bits/stl_queue.h:295:4: error: ‘class std::queue<Event, std::deque<Event, std::allocator<Event> > >’ has no member named ‘pop_front’
295 | c.pop_front();
| ~~^~~~~~~~~
I am not sure where I am going wrong or how to fix this error. Any help would be greatly appreciated

Answer 1

You have a dependency from queue to queue when you make a queue the container type used in the queue and queue does not satisfy all the requirements in itself.
I suggest using a std::deque as the default container instead, like it is by default for a queue.
So instead of
template<typename T, typename Container = std::queue<T>>
make it
template<typename T, typename Container = std::deque<T>>
From cppreference:
"The type of the underlying container to use to store the elements. The container must satisfy the requirements of SequenceContainer. Additionally, it must provide the following functions with the usual semantics:"
back()
front()
push_back()
pop_front()