是什么＆QUOT的目的;（无效）（{code}）QUOT;在C？ [英] what is the purpose of "(void) ( { CODE } )" in c?

问题描述

在C code的产生一块，我发现这样的事情（编辑）：

In a generated piece of c code I found something like this (edited):

#include <stdio.h>

int main() {

  (void) (
    {
      int i = 1;
      int y = 2;

      printf("%d %d\n", i,y);
    }
  );

  return 0;
}

我相信，我从来没有见过的构造（无效）（{code}）之前，我也不是能找出的目的可能是。

I believe I have never seen the construct (void) ( { CODE } ) before, nor am I able to figure out what the purpose might be.

那么，这是什么结构呢？

So, what does this construct do?

推荐答案

{} 是 GCC 扩展名为语句前pression 的

http://gcc.gnu.org/onlinedocs/gcc/Statement- Exprs.html

一个声明前pression产生一个值，（无效）投可能是这里删除编译器警告或作出明确的声明价值前pression不被使用。

A statement expression yields a value and the (void) cast is probably here to remove the compiler warning or to make explicit that the value of the statement expression is not used.

现在（无效）{} 是一样的简单复合语句 {} 并有没点用吧。

Now (void) ({ }) is the same as a simple compound statement {} and there is no point of using it.

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