Menu
My compiler doesn't support make_unique. How to write one?
template< class T, class... Args > unique_ptr<T> make_unique( Args&&... args ); 
843
A unique_ptr does not share its pointer. It cannot be copied to another unique_ptr , passed by value to a function, or used in any C++ Standard Library algorithm that requires copies to be made. A unique_ptr can only be moved.
Yes, all the elements will be value initialized by std::make_unique.
A unique_ptr object wraps around a raw pointer and its responsible for its lifetime. When this object is destructed then in its destructor it deletes the associated raw pointer. unique_ptr has its -> and * operator overloaded, so it can be used similar to normal pointer.
A little late, but make_unique can itself throw according to cppreference: make_unique "may throw std::bad_alloc or any exception thrown by the constructor of T. If an exception is thrown, this function has no effect." So how is that exception safe?
Version by Stephan T. Lavavej (also known by STL) who originally proposed adding this function to C++14
#include <cstddef> #include <memory> #include <type_traits> #include <utility> namespace std { template<class T> struct _Unique_if { typedef unique_ptr<T> _Single_object; }; template<class T> struct _Unique_if<T[]> { typedef unique_ptr<T[]> _Unknown_bound; }; template<class T, size_t N> struct _Unique_if<T[N]> { typedef void _Known_bound; }; template<class T, class... Args> typename _Unique_if<T>::_Single_object make_unique(Args&&... args) { return unique_ptr<T>(new T(std::forward<Args>(args)...)); } template<class T> typename _Unique_if<T>::_Unknown_bound make_unique(size_t n) { typedef typename remove_extent<T>::type U; return unique_ptr<T>(new U[n]()); } template<class T, class... Args> typename _Unique_if<T>::_Known_bound make_unique(Args&&...) = delete; } EDIT: updated code to the N3656 standard revision
142
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
