Comparison of C++ function pointers and callback functions

Function pointers and callback functions are both tools for implementing the callback mechanism. Function pointers are created at compile time and cannot be modified and need to be called explicitly; callback functions are created at runtime and can be dynamically bound to different functions and automatically called by the callback function. Therefore, function pointers are suitable for static callbacks, while callback functions are suitable for dynamic callbacks.

Comparison of C function pointers and callback functions

Function pointers and callback functions are both powerful tools used to implement the callback mechanism in C.

Function pointer

• is a pointer variable pointing to a function.
• Created at compile time and cannot be changed at runtime.
• Requires explicit call.

Callback function

• is a function that accepts a function pointer as a parameter.
• Created at runtime and can be dynamically bound to different functions.
• Automatically called by the callback function.

Practical Case

Consider an application that needs to perform different tasks at different times. We can achieve this functionality using the following code:

#include <iostream>

// 定义一个打印消息的函数
void print_message(const char* message) {
  std::cout << message << std::endl;
}

// 定义一个接受函数指针参数的回调函数
void execute_callback(void (*callback)(const char*)) {
  callback("Hello world!");
}

int main() {
  // 使用函数指针调用回调函数
  execute_callback(print_message);
  
  // 动态创建并调用回调函数
  auto lambda = [](const char* message) {
    std::cout << "[Lambda] " << message << std::endl;
  };
  execute_callback(lambda);

  return 0;
}

In this example, print_message is a function pointer for static callbacks. A lambda expression lambda is a dynamic callback that is created at runtime and bound to execute_callback.

Main difference

##ModabilityUnmodifiableCan be modifiedCalling methodExplicitAutomaticBinding staticdynamic

Features	Function pointer	Callback function
Creation timing	Compile time	Run time

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