Namespaces
Variants

    std::unique_ptr<T,Deleter>::reset

    From cppreference.com
     
    C++
     
    Memory management library
    (exposition only*)
    Allocators
    Uninitialized memory algorithms
    Constrained uninitialized memory algorithms
    Memory resources
    Uninitialized storage (until C++20)
    (until C++20*)
    (until C++20*)
    (until C++20*)

    Garbage collector support (until C++23)
    (C++11)(until C++23)
    (C++11)(until C++23)
    (C++11)(until C++23)
    (C++11)(until C++23)
    (C++11)(until C++23)
    (C++11)(until C++23)
     
    std::unique_ptr
     
    members of the primary template, unique_ptr<T>
    void reset( pointer ptr = pointer() ) noexcept;
    		 (1) (constexpr since C++23)
    members of the specialization unique_ptr<T[]>
    template< class U > void reset( U ptr ) noexcept;
    		 (2) (constexpr since C++23)
    void reset( std::nullptr_t = nullptr ) noexcept;
    		 (3) (constexpr since C++23)
    See More

    Replaces the managed object.

    1,2) Equivalent to auto old_ptr = get();
    /* assigns “ptr” to the stored pointer */
    if (old_ptr)
    get_deleter()(old_ptr);    .
    If get_deleter()(old_ptr) throws an exception, the behavior is undefined.
    2) This overload participates in overload resolution only if U is the same type as pointer, or all following conditions are satisfied:
    • pointer is the same type as element_type*.
    • U is a pointer type V* such that V(*)[] is convertible to element_type(*)[].
    3) Equivalent to reset(pointer()).

    Parameters

    ptr - pointer to a new object to manage

    Notes

    To replace the managed object while supplying a new deleter as well, move assignment operator may be used.

    A test for self-reset, i.e. whether ptr points to an object already managed by *this, is not performed, except where provided as a compiler extension or as a debugging assert. Note that code such as p.reset(p.release()) does not involve self-reset, only code like p.reset(p.get()) does.

    Example

    Run this code
    #include <iostream>
#include <memory>

struct Foo // object to manage
{
    Foo() { std::cout << "Foo...\n"; }
    ~Foo() { std::cout << "~Foo...\n"; }
};

struct D // deleter
{
    void operator() (Foo* p)
    {
        std::cout << "Calling delete for Foo object... \n";
        delete p;
    }
};

int main()
{
    std::cout << "Creating new Foo...\n";
    std::unique_ptr<Foo, D> up(new Foo(), D()); // up owns the Foo pointer (deleter D)
    
    std::cout << "Replace owned Foo with a new Foo...\n";
    up.reset(new Foo());  // calls deleter for the old one
    
    std::cout << "Release and delete the owned Foo...\n";
    up.reset(nullptr);      
}

    Output: 

    Creating new Foo...
Foo...
Replace owned Foo with a new Foo...
Foo...
Calling delete for Foo object...
~Foo...
Release and delete the owned Foo...
Calling delete for Foo object...
~Foo...

    Defect reports

    The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

    DR Applied to Behavior as published Correct behavior
    LWG 2118 C++11 unique_ptr<T[]>::reset rejected qualification conversions accepts
    LWG 2169 C++11 the overload unique_ptr<T[]>::reset(pointer) existed removed the overload

    See also

    		 returns a pointer to the managed object and releases the ownership
    (public member function) [edit]