C++核心准则C.84:swap函数不应该失败

钒铅矿

C.84: A swap function may not fail

C.84:swap函数不应该失败

Reason（原因）

swap is widely used in ways that are assumed never to fail and programs cannot easily be written to work correctly in the presence of a failing swap. The standard-library containers and algorithms will not work correctly if a swap of an element type fails.

swap函数被广泛地使用的方式就是假设它永远不会失败，而且也很难写出即使swap出错也能正常动作的程序。标准库容器和算法在元素交换失败时也无法正常工作。

Example, bad（反面示例）


void swap(My_vector& x, My_vector& y)
{
   auto tmp = x;   // copy elements
   x = y;
   y = tmp;
}


This is not just slow, but if a memory allocation occurs for the elements in tmp, this swap may throw and would make STL algorithms fail if used with them.

这段代码的问题不仅是慢，而且如果因为tmp的元素发生了内存申请，如果使用它的话，这个swap可能抛出异常并令STL算法失败。

Enforcement（实施建议）

(Simple) When a class has a swap member function, it should be declared noexcept.

(简单)如果类包含swap成员函数，它应该被声明为noexcept。

原文链接

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c84-a-swap-function-may-not-fail

---

觉得本文有帮助？请分享给更多人。

关注【面向对象思考】轻松学习每一天！

面向对象开发，面向对象思考！