std::unique_ptr<T,Deleter>::reset
From cppreference.com
< cpp | memory | unique ptr
C++
Feature test macros (C++20)
Concepts library (C++20)
Metaprogramming library (C++11)
Ranges library (C++20)
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Memory management library
Uninitialized memory algorithms
Constrained uninitialized memory algorithms
Memory resources
Uninitialized storage (until C++20)
Garbage collector support (until C++23)
(exposition only*)
(C++11)
(C++23)
(C++11)
(C++17)
(C++11)
(C++11)
(C++20)
(C++20)
(C++17)
(C++11)
(C++17)
(C++20)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
(until C++20*)
(until C++20*)
(until C++20*)
(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)
(C++11)
(C++11)
(C++17)
(C++20)
(C++17)
(C++11)
(C++11)
(C++11)
(until C++17*)
(C++11)
(C++17)
(C++26)
(C++26)
(C++11)
(C++11)
(C++11)
(C++23)
(C++23)
(C++11)
(C++20)
(C++11)
(C++11)
(C++20)
(C++26)
std::unique_ptr
unique_ptr::reset
(C++14)(C++20)
(until C++20)(C++20)
(C++20)
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( U ptr ) noexcept;
void reset( std::nullptr_t = nullptr ) noexcept;
(3)
(constexpr since C++23)
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);.
/* 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:
-
pointeris the same type aselement_type*. -
Uis a pointer typeV*such thatV(*)[]is convertible toelement_type(*)[].
3) Equivalent to reset(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. 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.
[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 |