函数参数的销毁顺序是什么？

Question

这是我之前问题的后续问题，因为我不小心混淆了参数和参数。感谢 Columbo 和 T.C。清除我在该问题的评论中的术语混淆。

如果某些函数的主体 f 的参数 p_1、...、p_n 类型为 T_1、...、T_n分别抛出异常，完成或returns，参数销毁的顺序是什么，为什么？如果可能，请提供对标准的引用。

示例：

template <typename ... Args>
void f(Args ... params) {} // in what order are params destroyed?

void f(T1 p1, T2 p2, T3 p3) {} // in what order are p1, p2 and p3 destroyed?

Answer 1

参数销毁的确切时间点是unspecified:

CWG decided to make it unspecified whether parameter objects are destroyed immediately following the call or at the end of the full-expression to which the call belongs.

构造参数的顺序也是未指定的，但是由于函数参数具有块作用域，虽然它们的构造顺序未指定，析构是构造的相反顺序.例如。考虑

#include <iostream>

struct A {
    int i;
    A(int i) : i(i) {std::cout << i;}
    ~A() {std::cout << '~' << i;} 
};

void f(A, A) {}

int main() {
    (f(0, 1), std::cout << "#");
}

打印 10#~0~1 with GCC and 01#~1~0 with Clang; they construct parameters in different orders, but both destroy in the reverse order of construction, at the end of the full-expression the call occurs in (rather than right after returning to the caller). VC++ prints 10~0~1#.

函数参数的销毁顺序是什么？

What is the order of destruction of function parameters?

c++

parameters

function

object-lifetime

language-lawyer