g++ vs intel/clang 参数传递顺序? [英] g++ vs intel/clang argument passing order?

问题描述

考虑以下代码(LWS):

#include <iostream>
#include <chrono>

inline void test(
   const std::chrono::high_resolution_clock::time_point& first, 
   const std::chrono::high_resolution_clock::time_point& second)
{
   std::cout << first.time_since_epoch().count() << std::endl;
   std::cout << second.time_since_epoch().count() << std::endl;
}

int main(int argc, char* argv[])
{
   test(std::chrono::high_resolution_clock::now(), 
        std::chrono::high_resolution_clock::now());
   return 0;
}

您必须多次运行它，因为有时没有明显的区别.但是当first和second的求值时间有明显差异时，g++下的结果如下:

You have to run it several times because sometimes, there is no visible difference. But when there is a visible difference between the time of evaluation of first and second, the result is the following under g++ :

1363376239363175
1363376239363174

以及 intel 和 clang 下的以下内容:

and the following under intel and clang :

1363376267971435
1363376267971436

这意味着在 g++ 下，首先评估 second 参数，而在 intel 和 clang 下，首先评估 first 参数.

It means that under g++, the second argument is evaluated first, and under intel and clang the first argument is evaluated first.

根据 C++11 标准，哪个是正确的?

Which one is true according to the C++11 standard?

推荐答案

根据 C++11 标准，哪个是正确的?

Which one is true according to the C++11 standard ?

两者都是允许的.引用标准(第 8.3.6 节):

Both are permissible. To quote the standard (§8.3.6):

函数参数的计算顺序未指定.

The order of evaluation of function arguments is unspecified.

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