C中的常量返回类型 [英] Const return types in C

问题描述

我正在阅读一些代码示例，他们返回了const int。当我尝试编译示例代码时，遇到关于返回类型冲突的错误。因此，我开始搜索，认为const是问题所在（当我删除它时，代码可以正常工作，不仅可以编译，而且可以按预期工作）。但是我永远无法找到专门与const返回类型有关的信息（我对结构/参数/等等等，但是没有返回类型）。因此，我尝试编写一段代码来简单地展示const可以做什么。我想出了这个：

I was reading some samples of code, and they returned a const int. When I tried to compile the examples code I got errors concerning conflicting return types. So I started searching, thinking that the const was the problem (when I removed it, the code worked fine, not only did it compile, but worked as expected). But I never was able to find information specifically pertaining to a const return type (I did for structures/parameters/etc. etc., but not return types). So I tried writing a piece of code to simply show what const may do. I came up with this:

#include <stdio.h>

int main() {
    printf("%i", method());
}

const int method() {
    return 5;
}

当我对此进行编译时，我得到：

And when I compile this, I get:

$ gcc first.c 
first.c:7: error: conflicting types for ‘method’
first.c:4: note: previous implicit declaration of ‘method’ was here

但是，每当删除const时，正如预期的那样，只需打印出5，就可以继续使用。因此，谁能告诉我const作为返回类型的含义。谢谢。

However, whenever I remove the const, it, as expected, simply prints out a 5, a continues on with life. So, can anyone tell me what const is supposed to mean when used as a return type. Thank you.

推荐答案

在调用method（）之前添加其原型将解决该错误。

Adding the prototype of method() before you call it will fix the error.

const int method();
int main() {
    printf("%i", method());
}

---

---

Line 7: error: conflicting types for 'method'

此错误告诉我们 method（）由编译器创建（因为找不到），其返回类型与 const int 不同（可能是int）。

This error tells us that method() was created by the compiler (because it didn't find it) with a different return type than const int (probably int).

Line 4: error: previous implicit declaration of 'method' was here

另一个错误告诉我们，实际上编译器创建了自己的版本的方法。

This other error tells us that in fact the compiler created its own version of method.

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