头文件中包含头文件 [英] Header files included in header files

问题描述

大家好


小组怎么看待将

中的一个头文件包含在另一个内的做法？


我已经完成了一些遗留代码，并且它创建了一个

依赖于一个模块（文件集合），这是不需要的，除了

对于一个头文件的内容。


我会说''不，头文件应该包含在C源代码中，而不是在另一个内容中

header''，但我总是遇到后者的强烈争论。


你怎么想，什么是公认的做法？


谢谢

JS

解决方案

文章< cd ********** @ newstree.wise.edt.ericsson.se>，

" John Smith" <所以***** @ microsoft.com>写道：

大家好

小组怎么想在
中包含一个头文件的做法？
<我已经完成了一些遗留代码，并且它创建了对模块（文件集合）的依赖，这对于一个头文件的内容除了
之外是不需要的。

我会说''不，头文件应该包含在C源代码中，而不是在另一个
头文件中'，但我总是遇到强有力的争论后者。

你怎么想，什么是公认的做法？

如果你写一个头文件header.h，然后它必须以单行源文件的方式写成

方式


#include" header.h"

编译没有错误。这意味着header.h需要包含完成这项工作所需的所有内容

，但不能更多。


注意一个函数可以有参数或返回值类型struct

xxx *没有struct xxx的声明;这个功能

的C经常使得不必在头文件中包含头文件

文件。

" Christian Bau" < CH *********** @ cbau.freeserve.co.uk>在消息中写道

news：ch ********************************* @ slb- newsm1.svr.pol.co.uk ...

在文章< cd ********** @ newstree.wise.edt.ericsson.se>中，
约翰史密斯 <所以***** @ microsoft.com>写道：

大家好

小组怎么想到从另一个里面包含一个头文件
的做法？
<我已经完成了一些遗留代码，并且它创建了对不需要的模块（文件集合）的依赖，
除了一个头文件的内容。

我会说''不，头文件应该包含在C源代码中，而不是
另一个头文件''，但我总是遇到强有力的争论后者。

你怎么想，什么是公认的做法？

如果你写一个头文件header.h，那么它必须是用这样的方式写的单行源文件
编译没有错误。这意味着header.h需要包含使这项工作成为必要的所有内容，而不是更多内容。

请注意，函数可以包含参数或返回类型为struct的值/> xxx *"没有struct xxx的声明; C的这个特性经常使得不必在头文件中包含头文件。

谢谢Christian


你有一个关于它必须编译的好点。这个特殊的标题

问题在第一个标题中有类似

typedef struct

{int array [THIS_IS_DEFINED_IN_HEADER2]; } astruct;


当然在另一个标题中

#define THIS_IS_DEFINED_IN_HEADER2 5


结果是是唯一依赖的东西！

正常练习，还是编码不好？


谢谢

JS

嗨John，

你对它必须编译有一个好处。这个特殊的标题问题在第一个标题中有类似
typedef struct
{int array [THIS_IS_DEFINED_IN_HEADER2]; } astruct;

当然在另一个标题中
#define THIS_IS_DEFINED_IN_HEADER2 5
这原来是唯一依赖的东西！
正常练习或者编码不好？

这取决于。我正在使用一个巨大的代码，你有数百个b $ b的头文件。许多THIS_IS_DEFINED_IN_HEADER2类型

符号常量是有意义的，因为您可以假设

所有数组（在您的示例中）服务于某个目的

具有相同的尺寸 - 我认为优点很明显。


另一方面，如果这个符号常数没有

a"更深"意思是你的数组的目的，但每次只有
你有数值5的值，

那么它编码很差。


如果您确定其含义，您还可以使用

构造，例如


#ifndef DONTWANNAINCLUDEIT

#include" header2.h"

#endif


#ifdef THIS_IS_DEFINED_IN_HEADER2

#define MY_ARRAY_SIZE THIS_IS_DEFINED_IN_HEADER2

#else

#define MY_ARRAY_SIZE 5

#endif


typedef struct {

int array [MY_ARRAY_SIZE];

} astruct;

干杯，

Michael

Hi all

What does the group think of the practise of including one header file from
inside another?

I have some legacy code where this has been done, and it creates a
dependency on a module (collection of files) which are not required, except
for one header file''s contents.

I''d say ''No, header files should be included in the C source, not in another
header'', but I''ve always come across strong arguments for the latter.

What do you think, and what is accepted practise?

Thanks
JS

解决方案

In article <cd**********@newstree.wise.edt.ericsson.se>,
"John Smith" <so*****@microsoft.com> wrote:

Hi all

What does the group think of the practise of including one header file from
inside another?

I have some legacy code where this has been done, and it creates a
dependency on a module (collection of files) which are not required, except
for one header file''s contents.

I''d say ''No, header files should be included in the C source, not in another
header'', but I''ve always come across strong arguments for the latter.

What do you think, and what is accepted practise?

If you write a header file "header.h", then it must be written in such a
way that the single line source file

#include "header.h"

compiles without errors. That means header.h needs to include everything
that is necessary to make this work, but not more.

Note that a function can have arguments or return values of type "struct
xxx *" without having the declaration of struct xxx around; this feature
of C often makes it unnecessary to include header files within header
files.

"Christian Bau" <ch***********@cbau.freeserve.co.uk> wrote in message
news:ch*********************************@slb-newsm1.svr.pol.co.uk...

In article <cd**********@newstree.wise.edt.ericsson.se>,
"John Smith" <so*****@microsoft.com> wrote:

Hi all

What does the group think of the practise of including one header file from inside another?

I have some legacy code where this has been done, and it creates a
dependency on a module (collection of files) which are not required, except for one header file''s contents.

I''d say ''No, header files should be included in the C source, not in another header'', but I''ve always come across strong arguments for the latter.

What do you think, and what is accepted practise?

If you write a header file "header.h", then it must be written in such a
way that the single line source file

#include "header.h"

compiles without errors. That means header.h needs to include everything
that is necessary to make this work, but not more.

Note that a function can have arguments or return values of type "struct
xxx *" without having the declaration of struct xxx around; this feature
of C often makes it unnecessary to include header files within header
files.

Thanks Christian

You have a good point about it having to compile. This particular header
problem has, in the first header, something like
typedef struct
{ int array[THIS_IS_DEFINED_IN_HEADER2]; } astruct;

and of course in the other header
#define THIS_IS_DEFINED_IN_HEADER2 5

This turns out to be the only dependant thing!
Normal practise, or poor coding?

Thanks
JS

Hi John,

You have a good point about it having to compile. This particular header
problem has, in the first header, something like
typedef struct
{ int array[THIS_IS_DEFINED_IN_HEADER2]; } astruct;

and of course in the other header
#define THIS_IS_DEFINED_IN_HEADER2 5

This turns out to be the only dependant thing!
Normal practise, or poor coding?

It depends. I am working with a huge code where you have hundreds
of header files. Many of the THIS_IS_DEFINED_IN_HEADER2 type
symbolic constants make sense insofar as you then can assume
that all arrays (in your example) serving a certain purpose
are of the same size -- the advantages are clear, I think.

On the other hand, if this symbolic constant does not have
a "deeper" meaning for the purpose of your array but only has
per chance the value 5 which you also have as the array size,
then it is poor coding.

If you are sure about the implications, you can also use a
construct like

#ifndef DONTWANNAINCLUDEIT
#include "header2.h"
#endif

#ifdef THIS_IS_DEFINED_IN_HEADER2
#define MY_ARRAY_SIZE THIS_IS_DEFINED_IN_HEADER2
#else
#define MY_ARRAY_SIZE 5
#endif

typedef struct {
int array[MY_ARRAY_SIZE];
} astruct;
Cheers,
Michael

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