如何最好地在C中使用const关键字？ [英] How do I best use the const keyword in C?

问题描述

我试图了解如何在C代码中使用 const 。首先，我并没有真正使用它，但是后来，我看到了很多使用 const 的例子。我应该努力然后回过头来认真地做一些合适的变量 const 吗？还是我会浪费时间？

I am trying to get a sense of how I should use const in C code. First I didn't really bother using it, but then I saw a quite a few examples of const being used throughout. Should I make an effort and go back and religiously make suitable variables const? Or will I just be waisting my time?

我想它可以使人们更容易地阅读预期会改变的变量，特别是在函数调用中，无论是对人类还是对编译器。我是否还缺少其他要点？

I suppose it makes it easier to read which variables that are expected to change, especially in function calls, both for humans and the compiler. Am I missing any other important points?

推荐答案

const 是 typed ， #define 宏不是。

const 受C块限制， #define 适用于文件（或更严格地说，是编译单元）。

const is scoped by C block, #define applies to a file (or more strictly, a compilation unit).

const 与参数传递最有用。如果您看到带有指针的原型上使用了 const ，则表示传递数组或结构是安全的，因为该函数不会更改它。没有 const 也是可以的。

const is most useful with parameter passing. If you see const used on a prototype with pointers, you know it is safe to pass your array or struct because the function will not alter it. No const and it can.

看一下 strcpy（）的定义。 ，您会明白我的意思。首先将 const-ness应用于函数原型。改型 const 并不困难，而只是很多工作（但是如果按小时支付，可以。）。

Look at the definition for such as strcpy() and you will see what I mean. Apply "const-ness" to function prototypes at the outset. Retro-fitting const is not so much difficult as "a lot of work" (but OK if you get paid by the hour).

还要考虑：

const char *s = "Hello World";
char *s = "Hello World";

这是正确的，为什么？

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