标准C ++ 11是否保证传递给函数的临时对象在函数调用之前已创建？ | 11是否保证传递给函数的临时对象在函数调用之前已创建

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问题描述

标准C ++ 11保证在开始执行函数之前已经创建了所有3个临时对象？

即使临时对象传递为：

物件

rvalue-reference

对象

解决方案

：

Does standard C++11 guarantee that all 3 temporary objects have been created before the beginning performe the function?

Even if temporary object passed as:

object
rvalue-reference
passed only member of temporary object

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;
}

Output:

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

Working Draft, Standard for Programming Language C++ 2016-07-12: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf

But can be any of T created after func-start?

Or is there any way to pass arguments as g/r/l/x/pr-value so that the function started before the temporary object be created?

解决方案

[intro.execution]/16:

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