blocks|key|5144176|text|在您的(公共)头文件中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5144177|typedef+struct+point+point;|code-block|syntax|javascript|5144178|在.c文件中：|offset|length|style|CODE|5144179|struct+point
{
++++void+*data;
};|5144180|请注意，您的代码用户将不再能够在堆栈上创建point，因为编译器不知道它有多大。您可能需要提供一个point_create()函数来分配内存并将其地址返回给调用者。|5144181|entityMap^0|0|0|1|2|0|0|L|5|1D|E|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@$I|V|J|W|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Y|8|@$I|Z|J|10|K|L]|$I|11|J|12|K|L]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|R|$]]

In your (public) header file:

<pre><code>typedef struct point point;
</code></pre>

In your <code>.c</code> file:

<pre><code>struct point
{
 void *data;
};
</code></pre>

Note that users of your code will no longer be able to create a <code>point</code> on the stack, as the compiler doesn't know how big it is. You may have to provide a <code>point_create()</code> function which allocates memory and returns its address to the caller.

blocks|key|5144152|text|这是指向实现或pimpl惯用法的指针。有关C%2B%2B的教程，请参阅http://en.wikibooks.org/wiki/C%2B%2B_Programming/Idioms#Pointer_To_Implementation_.28pImpl.29，但这个想法也应该适用于C语言。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|5144153|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikibooks.org/wiki/C%2B%2B_Programming/Idioms#Pointer_To_Implementation_.28pImpl.29^0|7|5|G|3C|V|2H|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@$9|S|A|T|1|U]]|E|$]]|$1|F|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

This is the pointer to implementation or pimpl idiom. See <a href="http://en.wikibooks.org/wiki/C++_Programming/Idioms#Pointer_To_Implementation_.28pImpl.29" rel="nofollow">http://en.wikibooks.org/wiki/C++_Programming/Idioms#Pointer_To_Implementation_.28pImpl.29</a> for a tutorial for C++, but the idea should work in C as well.

blocks|key|5144202|text|typedef+struct+{
++++/*+private+members;+don't+access+directly+*/
++++void+*data;
}+point;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|5144203|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>typedef struct {
 /* private members; don't access directly */
 void *data;
} point;
</code></pre>

blocks|key|3544646|text|您可以有单独的公有头文件和私有头文件。一些库对此有约定：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3544647|3544648|Xt+(X11)+->+header.h和headerP.h，例如：X11/Vendor.h+vs+X11/VendorP.h|unordered-list-item|offset|length|style|CODE|3544649|Qt+->+header.h+vs+private/header_p.h，例如：qapplication.h+vs+#en1#|3544650|3544651|entityMap^0|0|0|C|8|L|9|Y|C|1E|D|0|6|8|I|I|14|E|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|P|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|Q|8|@$F|R|G|S|H|I]|$F|T|G|U|H|I]|$F|V|G|W|H|I]|$F|X|G|Y|H|I]]|9|@]|A|$]]|$1|J|3|K|5|E|7|Z|8|@$F|10|G|11|H|I]|$F|12|G|13|H|I]|$F|14|G|15|H|I]]|9|@]|A|$]]|$1|L|3|-4|5|6|7|16|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|N|$]]

You can have separate public header and private header files. Some libraries have conventions for this:

<ul>
<li>Xt (X11) -> <code>header.h</code> and <code>headerP.h</code>, e.g: <code>X11/Vendor.h</code> vs <code>X11/VendorP.h</code></li>
<li>Qt -> <code>header.h</code> vs <code>private/header_p.h</code>, e.g: <code>qapplication.h</code> vs <code>private/qapplication_p.h</code></li>
</ul>

blocks|key|1477728|text|如果您不想使用声明方法(例如，因为您希望库用户访问结构的其他成员)，则约定在私有成员前面加上下划线，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1477729|typedef+struct+{
++++void+*+_data;
}+point;|code-block|syntax|javascript|1477730|当然，如果人们真的愿意的话，他们仍然可以访问_data+(就像人们可以通过在includes之前添加#define+private+public来访问C%2B%2B中的私有数据一样)，但这是他们自己的责任；至少您已经指出，如果他们希望您的库按照应该的方式运行，就不应该这么做。|offset|length|style|CODE|1477731|entityMap^0|0|0|M|5|1E|M|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

If you do not want to use the declaration method (because you want the library user to access other members of your struct, for example) it is convention to prepend private member with an underscore, like this:

<pre><code>typedef struct {
 void * _data;
} point;
</code></pre>

Of course people could still access <code>_data</code> if they would really want to (just like people can access private data in C++ by adding a <code>#define private public</code> before their includes) but that is their own responsibility; at least you have indicated that they shouldn't do that if they want your library to behave as it should.

blocks|key|1477755|text|我使用这种方法是为了让客户在他的堆栈中分配模块实例。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1477756|struct+module_private+{
++++int+data;
}

typedef+uint8_t+module_t+[sizeof+(struct+module_private)+];|code-block|syntax|javascript|1477757|客户端将能够看到私有结构内容，但在不执行不应该进行的强制转换的情况下无法访问它。|1477758|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I use this approach in order to let client alloc the module instance in his STACK.

<pre><code>struct module_private {
 int data;
}

typedef uint8_t module_t [sizeof (struct module_private) ];
</code></pre>

Client will be able to see private struct content, but not access it without doing a cast that he shouldn't.

blocks|key|2092102|text|使用以下解决方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2092103|#include+<stdio.h>

#define+C_PRIVATE(T)++++++++struct+T##private+{
#define+C_PRIVATE_END+++++++}+private;

#define+C_PRIV(x)+++++++++++((x).private)
#define+C_PRIV_REF(x)+++++++(&(x)->private)

struct+T+{
++++int+a;

C_PRIVATE(T)
++++int+x;
C_PRIVATE_END
};

int+main()
{
++++struct+T++t;
++++struct+T+*tref+=+&t;

++++t.a+=+1;
++++C_PRIV(t).x+=+2;

++++printf("t.a+=+%25d\nt.x+=+%25d\n",+t.a,+C_PRIV(t).x);

++++tref->a+=+3;
++++C_PRIV_REF(tref)->x+=+4;

++++printf("tref->a+=+%25d\ntref->x+=+%25d\n",+tref->a,+C_PRIV_REF(tref)->x);

++++return+0;
}|code-block|syntax|javascript|2092104|结果是：|2092105|t.a+=+1
t.x+=+2
tref->a+=+3
tref->x+=+4|2092106|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Use the following workaround:

<pre><code>#include &lt;stdio.h&gt;

#define C_PRIVATE(T) struct T##private {
#define C_PRIVATE_END } private;

#define C_PRIV(x) ((x).private)
#define C_PRIV_REF(x) (&amp;(x)-&gt;private)

struct T {
 int a;

C_PRIVATE(T)
 int x;
C_PRIVATE_END
};

int main()
{
 struct T t;
 struct T *tref = &amp;t;

 t.a = 1;
 C_PRIV(t).x = 2;

 printf("t.a = %d\nt.x = %d\n", t.a, C_PRIV(t).x);

 tref-&gt;a = 3;
 C_PRIV_REF(tref)-&gt;x = 4;

 printf("tref-&gt;a = %d\ntref-&gt;x = %d\n", tref-&gt;a, C_PRIV_REF(tref)-&gt;x);

 return 0;
}
</code></pre>

Result is:

<pre><code>t.a = 1
t.x = 2
tref-&gt;a = 3
tref-&gt;x = 4
</code></pre>

I define a structure in a header file like so:

<pre><code>typedef struct {
 void *data;
} point;
</code></pre>

I want to keep other people from accessing *data directly, so I thought I'd declare the structure in the .c file instead and use something like <code>extern typedef struct point;</code> in the header file. That doesn't work however.

What's the best way to achieve this?

How to make struct members private?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我在头文件中定义了一个结构，如下所示：typedef struct {    void *data;} point;我想防止其他人直接访问*数据，所以我想我应该在.c文件中声明结构，并在头文件中使用类似extern typedef struct point;的内容。然而，这并不起作用。实现这一目标的最好方法是什么？

问如何让struct成员成为私有的？
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回答 7

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问如何让struct成员成为私有的？
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