Is this code fragment valid? :
这段代码片段有效吗? :
unique_ptr<A> p( new A());
p = nullptr;
That is, can I assign nullptrto a unique_ptr ? or it will fail?
也就是说,我可以指定nullptrto一个unique_ptr吗?还是会失败?
I tried this with the g++ compiler and it worked, but what about other compilers?
我用g ++编译器尝试了这个并且它有效,但是其他编译器呢?
1 个解决方案
#1
28
It will work.
它会工作。
From Paragraphs 20.7.1.2.3/8-9 of the C++11 Standard about the unique_ptr<> class template:
从C ++ 11标准的第20.7.1.2.3 / 8-9段开始,关于unique_ptr <>类模板:
unique_ptr& operator=(nullptr_t) noexcept;unique_ptr&operator =(nullptr_t)noexcept;
Effects:
reset().Postcondition:
get() == nullptr后置条件:get()== nullptr
This means that the definition of class template unique_ptr<> includes an overload of operator = that accepts a value of type nullptr_t (such as nullptr) as its right hand side; the paragraph also specifies that assigning nullptr to a unique_ptr is equivalent to resetting the unique_ptr.
这意味着类模板unique_ptr <>的定义包括operator =的重载,它接受类型为nullptr_t的值(例如nullptr)作为其右侧;该段还指定将nullptr分配给unique_ptr等同于重置unique_ptr。
Thus, after this assignment, your A object will be destroyed.
因此,在此赋值之后,您的A对象将被销毁。
#1
28
It will work.
它会工作。
From Paragraphs 20.7.1.2.3/8-9 of the C++11 Standard about the unique_ptr<> class template:
从C ++ 11标准的第20.7.1.2.3 / 8-9段开始,关于unique_ptr <>类模板:
unique_ptr& operator=(nullptr_t) noexcept;unique_ptr&operator =(nullptr_t)noexcept;
Effects:
reset().Postcondition:
get() == nullptr后置条件:get()== nullptr
This means that the definition of class template unique_ptr<> includes an overload of operator = that accepts a value of type nullptr_t (such as nullptr) as its right hand side; the paragraph also specifies that assigning nullptr to a unique_ptr is equivalent to resetting the unique_ptr.
这意味着类模板unique_ptr <>的定义包括operator =的重载,它接受类型为nullptr_t的值(例如nullptr)作为其右侧;该段还指定将nullptr分配给unique_ptr等同于重置unique_ptr。
Thus, after this assignment, your A object will be destroyed.
因此,在此赋值之后,您的A对象将被销毁。