std::make_unique with null pointer?

Question

I have not been able to find any documentation about what happens if I pass a null pointer to std::make_unique.

Is an exception thrown?

Answer 1

std::make_unique forwards all the arguments passed to a matching target constructor. Therefore, if you pass nullptr, it will search for a constructor that accepts nullptr_t (or any matching constructor). If it is not there, it will fail to compile.

class A
{
public:
   A(void*) { ... } // could also be A(int*) or template <typename T> A(T*)
};

...
std::make_unique<A>(nullptr); // constructs an A by calling A(void*), passing nullptr.