std::unique_ptr<T,Deleter>::reset
| 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 to
auto old_ptr = get();/* assigns “ptr” to the stored pointer */if (old_ptr)get_deleter()(old_ptr);.
If
2) This overload participates in overload resolution only if get_deleter()(old_ptr) throws an exception, the behavior is undefined.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()).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
#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) |
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