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std::shared_ptr::use_count(3)  C++ Standard Libary std::shared_ptr::use_count(3)

NAME
     std::shared_ptr::use_count - std::shared_ptr::use_count

Synopsis
	long use_count() const noexcept;

	Returns  the  number  of  different shared_ptr instances (this included)
     managing the
	current object. If there is no managed object, 0 is returned.

	In multithreaded environment, the value returned by use_count is approx-
     imate
	(typical implementations use a memory_order_relaxed load).

Parameters
	(none)

Return value
	The number of std::shared_ptr instances managing the current object or 0
     if there is
	no managed object.

Notes
	Common use cases include

	  * comparison with 0. If use_count returns zero, the shared pointer  is
     empty and
	    manages no objects (whether or not its stored pointer is nullptr).
	  *  comparison  with 1. If use_count returns 1, there are no other own-
     ers.
	    The
	    deprecated
	    (since C++17) member function unique()  is	provided  for  this  use
     case.
	    (until C++20) In multithreaded environment, this does not imply that
     the object
	    is	safe  to modify because accesses to the managed object by former
     shared owners
	    may not have completed, and because new shared owners may be  intro-
     duced
	    concurrently, such as by std::weak_ptr::lock.

Example
     // Run this code

      #include <iostream>
      #include <memory>

      void fun(std::shared_ptr<int> sp)
      {
	  std::cout << "in fun(): sp.use_count() == " << sp.use_count()
		    << " (object @ " << sp << ")\n";
      }

      int main()
      {
	  auto sp1 = std::make_shared<int>(5);
	  std::cout << "in main(): sp1.use_count() == " << sp1.use_count()
		    << " (object @ " << sp1 << ")\n";

	  fun(sp1);
      }

Possible output:
      in main(): sp1.use_count() == 1 (object @ 0x20eec30)
      in fun(): sp.use_count() == 2 (object @ 0x20eec30)

See also
	unique	       checks  whether the managed object is managed only by the
     current
	(until C++20) shared_ptr object
		      (public member function)

http://cppreference.com 	   2024.06.10	   std::shared_ptr::use_count(3)
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