C 语言中的 OOP，实现和错误 [英] OOP in C, implementation and a bug

问题描述

我正在尝试在 C 中探索 OOP.然而，我是一个 C n00b 并且想挑选 stackoverflow 的聪明大脑:)

I am trying to explore OOP in C. I am however a C n00b and would like to pick the brilliant brains of stackoverflow :)

我的代码如下:

#include <stdio.h>
#include <stdlib.h>

typedef struct speaker {
    void (*say)(char *msg);
} speaker;

void say(char *dest) {
  printf("%s",dest);
}

speaker* NewSpeaker() {
  speaker *s;
  s->say = say;
  return s;
}

int main() {
  speaker *s = NewSpeaker();
  s->say("works");
}

但是我从中得到了一个段错误，如果我从 say 中删除所有 args 并使其无效，我可以让它正常工作.我当前的代码有什么问题?

However I'm getting a segfault from this, if I however remove all args from say and make it void, I can get it to work properly. What is wrong with my current code?

还有.虽然这在 C 中实现了一种对象形式，但我试图通过继承来进一步实现它，甚至覆盖/重载方法.您认为我如何实现这样的功能?

Also. While this implements a form of object in C, I'm trying to further implement it with inheritance, and even overriding/overloading of methods. How do you think I can implement such?

谢谢！

推荐答案

在您的代码中，NewSpeaker() 实际上并未创建新"扬声器.您需要使用内存分配函数，例如 malloc 或 calloc.

In your code, NewSpeaker() doesn't actually create a "new" speaker. You need to use a memory allocation function such as malloc or calloc.

speaker* NewSpeaker() {
   speaker *s = malloc(sizeof(speaker));
   s->say = say;
   return s;
}

没有赋值，例如 malloc 的返回值，s 被初始化为堆栈上的垃圾，因此是段错误.

Without assigning the value from, for example, the return value of malloc, s is initialized to junk on the stack, hence the segfault.

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