Przejdź do głównej zawartości
// 1)
constexpr void reset( pointer ptr = pointer() ) noexcept;

Description

Replaces the managed object.

1)

Given current_ptr, the pointer that was managed by *this, performs the following actions, in this order:

  • Saves a copy of the current pointer old_ptr = current_ptr
  • Overwrites the current pointer with the argument current_ptr = ptr
  • If the old pointer was non-empty, deletes the previously managed object if(old_ptr) get_deleter()(old_ptr).

2)

Behaves the same as the reset member of the primary template, except that it will only participate in overload resolution if either

  • U is the same type as pointer, or
  • pointer is the same type as element_type* and 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

Return value

(none)

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

#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);
}

Result
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.

DRApplied toBehavior as publishedCorrect behavior
LWG 2118C++11unique_ptr<T[]>::reset rejected qualification conversionsaccepts
// 1)
constexpr void reset( pointer ptr = pointer() ) noexcept;

Description

Replaces the managed object.

1)

Given current_ptr, the pointer that was managed by *this, performs the following actions, in this order:

  • Saves a copy of the current pointer old_ptr = current_ptr
  • Overwrites the current pointer with the argument current_ptr = ptr
  • If the old pointer was non-empty, deletes the previously managed object if(old_ptr) get_deleter()(old_ptr).

2)

Behaves the same as the reset member of the primary template, except that it will only participate in overload resolution if either

  • U is the same type as pointer, or
  • pointer is the same type as element_type* and 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

Return value

(none)

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

#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);
}

Result
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.

DRApplied toBehavior as publishedCorrect behavior
LWG 2118C++11unique_ptr<T[]>::reset rejected qualification conversionsaccepts