如何实现＆QUOT;民营/限制＆QUOT;在C函数？ [英] How to implement a "private/restricted" function in C?

问题描述

我是一个C面试中问了一个很有趣的问题：你怎么能实现一个函数f（）以这样一种方式，它只能从一个特定克（）函数被调用。如果不是G其他（）函数试图调用f（）的话，就会造成编译错误。

I was asked a very interesting question during a C interview: How can you implement a function f() in such a way that it can only be called from a particular g() function. If a function other than g() tries to call f() it would result in a compiler error.

起初，我以为这可能是与函数指针做，我能得到接近堵在运行时调用。但我无法想象一个编译时的策略。我甚至不知道这是否使用ANSI C是可能的。

At first, I though this could be done with function pointers and I could get close to blocking the call at runtime. But I was not able to think of a compile time strategy. I don't even know if this is possible using ansi C.

没有人有任何想法？

推荐答案

下面是一种方法：

int f_real_name(void)
{
    ...
}

#define f f_real_name
int g(void)
{
    // call f()
}
#undef f

// calling f() now won't work

另一种方式，如果你能保证 F（）和克（）是唯一的功能，在文件，正在申报 F（）为静态。

Another way, if you can guarantee that f() and g() are the only functions in the file, is to declare f() as static.

编辑：另一个宏把戏引起编译器错误：

Another macro trick to cause compiler errors:

static int f(void) // static works for other files
{
    ...
}

int g(void)
{
    // call f()
}
#define f call function

// f() certainly produces compiler errors here

这篇关于如何实现＆QUOT;民营/限制＆QUOT;在C函数？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！