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Table of Contents
Using function pointers
Use std::function and Lambda expressions
Using template generics
Tips: Be careful about lambdas that capture context
Home Backend Development C++ How to pass a function as a parameter in C ?

How to pass a function as a parameter in C ?

Jul 12, 2025 am 01:34 AM
Function parameters c++

In C, there are three main ways to pass functions as parameters: using function pointers, std::function and Lambda expressions, and template generics. 1. Function pointers are the most basic method, suitable for simple scenarios or C interface compatible, but poor readability; 2. std::function combined with Lambda expressions is a recommended method in modern C, supporting a variety of callable objects and being type-safe; 3. Template generic methods are the most flexible, suitable for library code or general logic, but may increase the compilation time and code volume. Lambdas that capture context must be passed through std::function or template and cannot be converted directly into function pointers.

How to pass a function as a parameter in C ?

In C, passing a function as a parameter to another function is actually a very common requirement, such as it is often used in callback mechanisms, algorithm encapsulation or event processing. There are several implementation methods, each with applicable scenarios. Here are several commonly used methods.

How to pass a function as a parameter in C ?

Using function pointers

This is the most basic and traditional way. C supports passing the address of a function as a parameter to other functions and calling it through function pointers.

How to pass a function as a parameter in C ?
 void greet() {
    std::cout << "Hello!" << std::endl;
}

void callFunction(void (*func)()) {
    func();
}

callFunction(greet); // Output Hello!
  • The function pointer type must match: the return value type and parameter list must be the same.
  • The readability is average, especially when the function signature is complex, it is prone to errors.
  • Suitable for simple scenarios or C-interface compatible.

Use std::function and Lambda expressions

C 11 introduces std::function in the <functional> header file, which is a general function wrapper that can bind ordinary functions, lambda expressions, binding expressions, etc.

 #include <functional>
#include <iostream>

void callFunction(std::function<void()> func) {
    func();
}

void greet() {
    std::cout << "Hello!" << std::endl;
}

callFunction(greet); // Output Hello!

// Or use lambda
callFunction([]() { std::cout << "Hi there!" << std::endl; });
  • More flexible and supports a variety of callable objects.
  • Type-safe, clearer syntax.
  • It is one of the recommended ways of modern C programming.

Using template generics

If you want to be completely generalized and do not specify a specific function type, you can use a template to accept any callable object:

How to pass a function as a parameter in C ?
 template<typename Func>
void callFunction(Func func) {
    func();
}

callFunction([]() { std::cout << "From lambda" << std::endl; });
void greet() { std::cout << "Hello!" << std::endl; }
callFunction(&greet);
  • Very flexible and suitable for a variety of callable objects.
  • Because it is a template, multiple instances will be generated, which may increase the compilation time and code volume.
  • This is a perfect way if you are writing library code or general logic.

Tips: Be careful about lambdas that capture context

When you use a lambda with capture as a function parameter, you cannot directly receive it with a function pointer, you must use std::function or template method.

For example:

 int value = 42;
callFunction([value]() { std::cout << "Value is " << value << std::endl; });
  • The lambda that captures a variable cannot be converted into a function pointer.
  • So in this case, you can only use std::function or template to handle it.

Basically these are the methods. Choose different methods in different situations. Function pointers are suitable for simple and old projects, std::function and templates are more suitable for the development style of modern C.

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