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std::unique_ptr::reset(3) C++ Standard Libary std::unique_ptr::reset(3) NAME std::unique_ptr::reset - std::unique_ptr::reset Synopsis 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 > (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) Given current_ptr, the pointer that was managed by *this, per- forms the following actions, in this order: 1. Saves a copy of the current pointer old_ptr = current_ptr 2. Overwrites the current pointer with the argument current_ptr = ptr 3. 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, ex- cept that it will only participate in overload resolution if either 1. U is the same type as pointer, or 2. 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 exten- sion 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 // 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... Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior LWG 2118 C++11 unique_ptr<T[]>::reset rejected qualification accepts conversions See also release returns a pointer to the managed object and releases the ownership (public member function) http://cppreference.com 2022.07.31 std::unique_ptr::reset(3)
NAME | Synopsis | Parameters | Return value | Notes | Example | Output: | See also
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