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

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std::unique_ptr

Member functions
unique_ptr::unique_ptr
unique_ptr::~unique_ptr
unique_ptr::operator=
Modifiers
unique_ptr::release
unique_ptr::reset
unique_ptr::swap
Observers
unique_ptr::get
unique_ptr::get_deleter
unique_ptr::operator bool
unique_ptr::operator*unique_ptr::operator->
unique_ptr::operator[]
Non-member functions
make_uniquemake_unique_for_overwrite (C++14)(C++20)
operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(C++20)
operator<< (C++20)
swap(std::unique_ptr)
Helper classes
hash<std::unique_ptr>

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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)

Replaces the managed object.

1,2) Equivalent toauto old_ptr= get();
/* assigns “ptr” to the stored pointer */
if(old_ptr)
get_deleter()(old_ptr);.

Ifget_deleter()(old_ptr) throws an exception, the behavior is undefined.

2) This overload participates in overload resolution only ifU is the same type aspointer, or all following conditions are satisfied:

pointer is the same type aselement_type*.
U is a pointer typeV* such thatV(*)[] is convertible toelement_type(*)[].

3) Equivalent toreset(pointer()).

[edit]Parameters

ptr

pointer to a new object to manage

[edit]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. whetherptr 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 asp.reset(p.release()) does not involve self-reset, only code likep.reset(p.get()) does.

[edit]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...

[edit]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