试图返回用`NULL`构造的`std::unique_ptr`-Tryingtoreturna`std::unique_ptr`constructedwith`NULL`

6  

I think that what you want is an empty unique_ptr:

我认为你想要的是一个空的unique_ptr:

return std::unique_ptr();

It seems that you are looking for a pointer that points to no object (and is false when converted to bool).

看来你正在寻找一个指向没有对象的指针(当转换为bool时它是假的)。

6  

You can use the default constructor of std::unique_ptr.

您可以使用std :: unique_ptr的默认构造函数。

std::unique_ptr a1();
std::unique_ptr a2(nullptr);

a1 and a2 are unique pointers initialised empty (owns nothing).

a1和a2是初始化为空的唯一指针(不拥有任何内容)。

you can verify the emptiness of the pointers with the operator bool provided by the unique_ptr class:

您可以使用unique_ptr类提供的运算符bool验证指针的空白:

if (!a1) { // the smart pointer is empty
}

5  

What you want is

你想要的是什么

return {};

the {} return a default constructed object of whatever (class) type¹, and can be read "nothing". It works with smart pointers, optional, and most everything.

{}返回任何(类)type1的默认构造对象,并且可以读作“nothing”。它适用于智能指针,可选,以及大多数所有内容。

If your compiler lacks this

如果你的编译器没有这个

return std::unique_ptr();

will do it. Passing NULL to std::unique_ptr is not legal in C++11 anyhow (the constructor is ambiguous).

会做的。无论如何,将NULL传递给std :: unique_ptr在C ++ 11中是不合法的(构造函数是不明确的)。

You don't have a C++11 compiler. Any use of C++11 in your code is going to be error-prone.

您没有C ++ 11编译器。在代码中使用C ++ 11会容易出错。

¹ The proper wording is complicated. For a scalar (like int), this zero-initializes the value (which, in practice, sets the value to 0/null/0.0/'\0' etc).

1正确的措辞很复杂。对于标量(如int),这会对值进行零初始化(实际上,将值设置为0 / null / 0.0 /'\ 0'等)。