Why doesn't make_unique work with unique_ptr::reset?

c++, c++11, c++14, unique-ptr

Solution

`reset()` takes a pointer.

What you seem to want is simple move assignment:

#include <memory>
using namespace std;

int main() {
    unique_ptr<int[]> p = make_unique<int[]>(3);
    p = make_unique<int[]>(10);    
}

some compilers might still like you to specify the `std::move()` there, but it's not strictly required.

Problem

I tried compiling some C++ code with VS2013, and `unique_ptr::reset()` doesn't seem to work with `make_unique()`; a small compilable repro code snippet follows: ``` #include <memory> using namespace std; int main() { unique_ptr<int[]> p = make_unique<int[]>(3); p.reset(make_unique<int[]>(10)); } ``` Compiling from command-line: ``` C:\Temp\CppTests>cl /EHsc /W4 /nologo test.cpp ``` These are the errors from the MSVC compiler: ``` test.cpp(6) : error C2280: 'void std::unique_ptr<int [],std::default_delete<_Ty> >::reset<std::unique_ptr<_Ty,std::default_delete<_Ty>>>(_Ptr2)' : attempting to reference a deleted function with [ _Ty=int [] , _Ptr2=std::unique_ptr<int [],std::default_delete<int []>> ] C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\INCLUDE\memory(16 23) : see declaration of 'std::unique_ptr<int [],std::default_delete<_Ty>>::rese t' with [ _Ty=int [] ] ``` However, the following code seems to compile fine: ``` p = make_unique<int[]>(10); ``` What is the reason of this behavior? Why does `unique_ptr::operator=()` work with `make_unique()`, but `unique_ptr::reset()` doesn't?

Original source