Swap、reset and release

一、对ownership的操作:

1、swap、release

二、

cppreference std::unique_ptr

Modifiers
release	returns a pointer to the managed object and releases the ownership (public member function)
reset	replaces the managed object (public member function)
swap	swaps the managed objects (public member function)

cppreference std::shared_ptr

Modifiers
reset	replaces the managed object (public member function)
swap	swaps the managed objects (public member function)

std::shared_ptr::reset 通过 void reset() noexcept; 来 release ownership

stackoverflow Does using .reset() on a std::shared_ptr delete all instances # A

When you use .reset(), you are eliminating one owner of the pointer, but all of the other owners are still around. Here is an example:

#include <memory>
#include <cstdio>

class Test { public: ~Test() { std::puts("Test destroyed."); } };

int main()
{
    std::shared_ptr<Test> p = std::make_shared<Test>();
    std::shared_ptr<Test> q = p;
    std::puts("p.reset()...");
    p.reset();
    std::puts("q.reset()...");
    q.reset();
    std::puts("done");
    return 0;
}

The program output:

p.reset()...
q.reset()...
Test destroyed.
done

Note that p and q are both owners of the object, and once both p and q are reset, then the instance is destroyed.