'unique_ptr' is not a class template, implementing unique_ptr

Question

I have a piece of code that uses "unique_ptr", but the Arduino environment does now know about:

#include <memory> 

So i went to C++ reference https://en.cppreference.com/w/cpp/memory/unique_ptr

Defined in header "memory"

template<

    class T,
    class Deleter = std::default_delete<T>
> class unique_ptr;

template <

    class T,
    class Deleter
> class unique_ptr<T[], Deleter>;

Figured that it doesn't take much to "implement".

My H file looks like this:

class state_deleter {  // a deleter class with state
  int count_;
public:
  state_deleter() : count_(0) {}
  template <class T>
  void operator()(T* p) {
    Serial.prinln("[deleted #");
    delete p;
  }
};


template <
    class T,
    class Deleter
> class unique_ptr<T[], Deleter>;



template <class T> class Circular_Buffer {
private:
  unique_ptr<T[],state_deleter> buffer; 
  // i left non relevant code out
};

More info here: https://cplusplus.com/reference/memory/unique_ptr/ Manages the storage of a pointer, providing a limited garbage-collection facility, with little to no overhead over built-in pointers (depending on the deleter used). https://cplusplus.com/ref...nique_ptr/get_deleter/

So i added the above from CPP reference to the piece of code and by adding the "deleter", i removed error messages. But still one remains:

'unique_ptr' is not a class template

I have implemented pieces of code from CPP reference before if i don't had access to it or needed a slightly adapted version and it worked.

Can it be done?

What makes this a "template class" a smart pointer?

class T,
class Deleter

not much too see here in this class definition.

Answer 1

Found Header files with the declaration of "Unique_ptr" here:

https://github.com/zouxiaohang/TinySTL/blob/master/TinySTL/Memory.h

and

https://github.com/microsoft/STL/blob/main/stl/inc/memory