调用约定和评估秩序

问题描述

我知道，C ++不指定哪些参数传递给函数的顺序。但是，如果我们编写以下code：

 无效__cdecl FUNC（INT A，INT B，INT C）
{
       的printf（％D，％D，％D，A，B，C）;
}
诠释的main（）
{
   INT I = 10;
   FUNC（++我，我，我++）;
}
 

我们可以肯定地说，输出将 12,11,11 自的确保参数传递顺序是从右到左？

解决方案

按照标准，有两件事情你需要理解和区分：

Now, please note, __cdecl ensures only the first, not the second. Calling conventions decide only how the functions arguments will be passed, left-to-right or right-to-left; they can still be evaluated in ANY order!

Hope this clarifies your doubts regarding the calling conventions.

However, since these conventions are Microsoft compiler extension to C++, so your code is non-portable. In that case, you can see how MSVC++ compiler evaluates function arguments and be relax IF you don't want to run the same code on other platform!

---

func(++i, i, ++i);

Note that this particular code invokes undefined behavior, because i is incremented more than once without any intervening any sequence point.

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