这在C中是什么？ [英] What's this in C?

问题描述

静态无效（DEVICE_REQUEST）（无效）;


此行在C中声明什么？

我总是遇到这样的代码，但是我之前从未学过

。

它看起来像是函数的声明，但是为什么DEVICE_REQUEST必须引用（）引用
。

任何人都可以向我解释一下吗？非常感谢！

解决方案

zh ********* @ gmail.com 写道：

static void（DEVICE_REQUEST）（void）;

这是什么行声明在C？
我总是遇到这样的代码，但我以前从未学过
它看起来像是函数的声明，但为什么DEVICE_REQUEST必须任何人都可以向我解释这个问题？非常感谢！

好​​吧，如果你展示DEVICE_REQUEST是什么，它会有很大的帮助。


一个原因吧可能在括号中，如果它的#defined为：


#define DEVICE_REQUEST * some_name


然后请确保您的原始行将`some_name`声明为

指向函数的指针，该函数不带参数并返回void

（无）：


static void（* some_name）（void）;


它不是一个函数的声明，而是一个可以用来调用函数的指针。

调用一个函数。 br />

这是您正在寻找的答案吗？如果没有，请告诉我们

DEVICE_REQUEST是什么。


-

BR，Vladimir

zh ********* @ gmail.com 写道：

static void（DEVICE_REQUEST）（void）;

这一行在C中声明了什么？
我总是遇到这样的代码，但我之前从未学过
它看起来像是函数的声明，但为什么DEVICE_REQUEST必须由（）引用。

是的。括号是可选的，但是如果定义了一个名为

DEVICE_REQUEST的函数式宏，则括号会阻止宏替换。


-

Thad

zh ******* **@gmail.com 说：

static void（DEVICE_REQUEST）（void）;

这一行在C中声明了什么？


一个名为DEVICE_REQUEST的函数，它不带任何参数并且不返回

值，并且具有内部链接。

我是总是遇到这样的代码，但我以前从未学过
。
它看起来像是函数的声明，但为什么DEVICE_REQUEST必须被（）引用。

如果某个小丑已经完成了


#define DEVICE_REQUEST（x）someexpressioninvolving x


括号使预处理器停止执行通常的

替换。定义和调用必须类似

括号：


void（DEVICE_REQUEST）（无效）

{

;

}


int main（无效）

{

（ DEVICE_REQUEST）（）;

返回0;

}


-

Richard Heathfield

Usenet是一个奇怪的地方 - dmr 29/7/1999
http://www.cpax.org.uk

电子邮件：rjh在上面的域名（但显然放弃了www）

static void (DEVICE_REQUEST)(void);

What does this line declare in C?
I am always meeting some codes like this,but I have never learnt that
before.
It looks like a declaration of a function,but why DEVICE_REQUEST has to
be quoted by ( ).
Anyone can explain that to me? thanks a lot!

解决方案

zh*********@gmail.com wrote:

static void (DEVICE_REQUEST)(void);

What does this line declare in C?
I am always meeting some codes like this,but I have never learnt that
before.
It looks like a declaration of a function,but why DEVICE_REQUEST has to
be quoted by ( ).
Anyone can explain that to me? thanks a lot!

Well, it would have helped a lot if you showed what DEVICE_REQUEST is.

One reason it might be in parentheses is if it''s #defined as:

#define DEVICE_REQUEST *some_name

Parenthese then make sure your original line declares `some_name` as a
pointer to a function which takes no parameters and returns void
(nothing):

static void (*some_name)(void);

It is not a declaration of a function, but a pointer you can use to
call a function.

Is this the answer you were looking for? If not, let us know what
DEVICE_REQUEST is.

--
BR, Vladimir

zh*********@gmail.com wrote:

static void (DEVICE_REQUEST)(void);

What does this line declare in C?
I am always meeting some codes like this,but I have never learnt that
before.
It looks like a declaration of a function,but why DEVICE_REQUEST has to
be quoted by ( ).

It is. The parentheses are optional, but if a function-like macro named
DEVICE_REQUEST is defined, the parentheses prevent macro substitution.

--
Thad

zh*********@gmail.com said:

static void (DEVICE_REQUEST)(void);

What does this line declare in C?
A function called DEVICE_REQUEST, which takes no parameters and returns no
value, and which has internal linkage.
I am always meeting some codes like this,but I have never learnt that
before.
It looks like a declaration of a function,but why DEVICE_REQUEST has to
be quoted by ( ).

If some clown has done

#define DEVICE_REQUEST(x) someexpressioninvolving x

the parentheses stop the preprocessor from performing the usual
substitution. The definition and call would have to be similarly
parenthesised:

void (DEVICE_REQUEST)(void)
{
;
}

int main(void)
{
(DEVICE_REQUEST)();
return 0;
}

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)

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