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;
Replaces the managed object.
1,2) Equivalent to auto old_ptr = get();
/* assigns âptrâ 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()).
[edit] Parameters ptr - pointer to a new object to manage [edit] NotesTo 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#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++11unique_ptr<T[]>::reset rejected qualification conversions accepts LWG 2169 C++11 the overload unique_ptr<T[]>::reset(pointer) existed removed the overload [edit] See also returns a pointer to the managed object and releases the ownership
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