微信公众号搜"智元新知"关注
微信扫一扫可直接关注哦!

标准C 11是否保证在函数调用之前创建传递给函数的临时对象?

标准C 11是否保证在开始执行函数之前创建了所有3个临时对象?

即使临时对象传递为:

>对象
> rvalue-reference
>仅传递临时对象的成员

http://ideone.com/EV0hSP

#include <iostream>
using namespace std;

struct T { 
    T() { std::cout << "T created \n"; }
    int val = 0;
    ~T() { std::cout << "T destroyed \n"; }
};

void function(T t_obj,T &&t,int &&val) {
    std::cout << "func-start \n";
    std::cout << t_obj.val << "," << t.val << "," << val << std::endl;
    std::cout << "func-end \n";
}

int main() {

    function(T(),T(),T().val);

    return 0;
}

输出

T created 
T created 
T created 
func-start 
0,0
func-end 
T destroyed 
T destroyed 
T destroyed

工作草案,编程语言标准C 2016-07-12:http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf

§ 5.2.2 Function call

§ 5.2.2

1 A function call is a postfix
expression followed by parentheses containing a possibly empty,
comma-separated list of initializer-clauses which constitute the
arguments to the function.

但是可以在func-start之后创建T中的任何一个吗?

或者有没有办法将参数作为g / r / l / x / pr-value传递,以便在创建临时对象之前启动函数

enter image description here

解决方法

[intro.execution]/16

When calling a function (whether or not the function is inline),every value computation and side effect associated with any argument expression,or with the postfix expression designating the called function,is sequenced before execution of every expression or statement in the body of the called function.

版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 dio@foxmail.com 举报,一经查实,本站将立刻删除。

相关推荐