c++ - 具有默认参数构造的 noexcept 说明符

Question

以下面的示例代码为例:

void test(const Item& item = Item()) {
   ...
}

假设一旦 item 被传递给函数，this 就不能抛出。

问题是:函数应该标记为noexcept还是noexcept(noexcept(Item()))？

IHMO，前者应该没问题，但我不确定。非常感谢标准的引用!

Answer 1

默认参数是函数调用者的快捷符号。所以，当函数执行时，构造就已经完成了。

因此，noexcept 应该就足够了。

在 standard [dcl.fct.default] 状态:

If an initializer-clause is specified in a parameter-declaration this initializer-clause is used as a default argument. Default arguments will be used in calls where trailing arguments are missing.

Example: the declaration void point(int = 3, int = 4); declares a function that can be called with zero, one, or two arguments of type int. It can be called in any of these ways: point(1,2); point(1); point(); The last two calls are equivalent to point(1,4) and point(3,4) , respectively.

还有一个注释(在[intro.execution]程序执行中):

Subexpressions involved in evaluating default arguments (8.3.6) are considered to be created in the expression that calls the function, not the expression that defines the default argument