不透明的C结构:声明它们的各种方法

问题描述

我已经看到了以下两种在C API中声明不透明类型的样式.在C中声明不透明结构/指针的各种方法是什么?使用一种样式比使用另一种样式有明显的优势吗?

I've seen both of the following two styles of declaring opaque types in C APIs. What are the various ways to declare opaque structs/pointers in C? Is there any clear advantage to using one style over the other?

// foo.h
typedef struct foo * fooRef;
void doStuff(fooRef f);

// foo.c
struct foo {
    int x;
    int y;
};

选项2

// foo.h
typedef struct _foo foo;
void doStuff(foo *f);

// foo.c
struct _foo {
    int x;
    int y;
};

推荐答案

我的投票是mouviciel发布并删除的第三个选项:

My vote is for the third option that mouviciel posted then deleted:

// foo.h
struct foo;
void doStuff(struct foo *f);

// foo.c
struct foo {
    int x;
    int y;
};

如果您真的不能忍受键入 struct 关键字，则可以接受 typedef struct foo foo; (注意:摆脱无用和有问题的下划线).但是无论您做什么，都从不使用 typedef 定义指针类型的名称.它隐藏了极其重要的信息，该类型的变量引用了一个对象，只要您将其传递给函数，就可以对其进行修改，并且可以处理不同限定(例如， const 限定)的对象.指针的版本是一大难题.

If you really can't stand typing the struct keyword, typedef struct foo foo; (note: get rid of the useless and problematic underscore) is acceptable. But whatever you do, never use typedef to define names for pointer types. It hides the extremely important piece of information that variables of this type reference an object which could be modified whenever you pass them to functions, and it makes dealing with differently-qualified (for instance, const-qualified) versions of the pointer a major pain.

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