c哥教你实盘操作(核心准证C.66:保证移动操作不会抛出异常)(1)

斜方砷铁矿与方解石

C.66: Make move operations noexcept

C.66:保证移动操作不会抛出异常

Reason(原因)

A throwing move violates most people's reasonably assumptions. A non-throwing move will be used more efficiently by standard-library and language facilities.

抛出异常的移动操作会破坏大多数人的符合逻辑的推测。不会抛出异常的移动可以被标准库和C 语言更加高效地使用。

Example(示例)

template<typename T> class Vector { public:    Vector(Vector&& a) noexcept :elem{a.elem}, sz{a.sz} { a.sz = 0; a.elem = nullptr; }    Vector& operator=(Vector&& a) noexcept { elem = a.elem; sz = a.sz; a.sz = 0; a.elem = nullptr; }    // ... private:    T* elem;    int sz; };

These operations do not throw.

这些操作都不会抛出异常。

Example, bad(反面示例)

template<typename T> class Vector2 { public:    Vector2(Vector2&& a) { *this = a; }             // just use the copy    Vector2& operator=(Vector2&& a) { *this = a; }  // just use the copy    // ... private:    T* elem;    int sz; };

This Vector2 is not just inefficient, but since a vector copy requires allocation, it can throw.

Vector2的问题不止是效率低,由于拷贝时需要分配内存,它可能还会抛出异常。

Enforcement(实施建议)

(Simple) A move operation should be marked noexcept.

(简单)移动操作应该被声明为noexcept。

原文链接

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c66-make-move-operations-noexcept


觉得本文有帮助?请分享给更多人。

更多精彩文章请关注微信公众号【面向对象思考】!

面向对象开发,面向对象思考!

,