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std::get_deleter(3)	      C++ Standard Libary	   std::get_deleter(3)

NAME
       std::get_deleter	- std::get_deleter

Synopsis
	  Defined in header <memory>
	  template<	   class	Deleter,	class	     T	     >
       (since C++11)
	  Deleter* get_deleter(	const std::shared_ptr<T>& p ) noexcept;

	  Access to the	p's deleter. If	the shared pointer p owns a deleter of
       type
	  cv-unqualified Deleter (e.g. if it was created with one of the  con-
       structors that
	  take	a  deleter  as	a  parameter),	then  returns a	pointer	to the
       deleter.	Otherwise,
	  returns a null pointer.

Parameters
	  p - a	shared pointer whose deleter needs to be accessed

Return value
	  A pointer to the owned deleter or nullptr. The returned  pointer  is
       valid at	least as
	  long as there	remains	at least one shared_ptr	instance that owns it.

Notes
	  The  returned	 pointer may outlive the last shared_ptr if, for exam-
       ple, std::weak_ptrs
	  remain and the implementation	doesn't	destroy	the deleter until  the
       entire control
	  block	is destroyed.

Example
	  demonstrates	that  std::shared_ptr  deleter	is  independent	of the
       shared_ptr's type

       // Run this code

	#include <iostream>
	#include <memory>

	struct Foo { int i; };
	void foo_deleter(Foo * p)
	{
	    std::cout << "foo_deleter called!\n";
	    delete p;
	}

	int main()
	{
	    std::shared_ptr<int> aptr;

	    {
		// create a shared_ptr that owns a Foo and a deleter
		auto foo_p = new Foo;
		std::shared_ptr<Foo> r(foo_p, foo_deleter);
		aptr = std::shared_ptr<int>(r, &r->i); // aliasing ctor
		// aptr	is now pointing	to an int, but managing	the whole Foo
	    } // r gets	destroyed (deleter not called)

	    // obtain pointer to the deleter:
	    if(auto del_p = std::get_deleter<void(*)(Foo*)>(aptr))
	    {
		std::cout << "shared_ptr<int> owns a deleter\n";
		if(*del_p == foo_deleter)
		    std::cout << "...and it equals &foo_deleter\n";
	    } else
		std::cout << "The deleter of shared_ptr<int> is	null!\n";
	} // deleter called here

Output:
	shared_ptr<int>	owns a deleter
	...and it equals &foo_deleter
	foo_deleter called!

See also
	  constructor	std::shared_ptr	constructors
			(public	member function)
	  get_deleter	returns	the deleter that is used  for  destruction  of
       the managed object
			(public	member function	of std::unique_ptr<T,Deleter>)

http://cppreference.com		  2022.07.31		   std::get_deleter(3)

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