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Difference between Macro and Inline Function.

Last Updated on August 9, 2023 by Mayank Dham

In the world of programming, functions are essential building blocks that help developers organize code and improve code reusability. Two commonly used function types are Macros and Inline Functions. While they both serve the purpose of code optimization and performance improvement, they have distinct characteristics and usage scenarios.

In this article, we explore the differences between Macros and Inline Functions. We delve into their definitions, implementations, advantages, and limitations. By understanding the nuances of these function types, developers can make informed decisions when choosing the most suitable approach for their specific programming needs. Join us on this informative journey to discover the contrast between Macros and Inline Functions and gain valuable insights into when to utilize each in your programming projects. Before directly moving to difference between macro and inline function, let’s first talk about inline functions.

Inline Function

An inline function is a regular function that is defined by the inline keyword. An inline function is a short function that is expanded by the compiler. And its arguments are evaluated only once. Inline functions are short-length functions that are created automatically without the use of the inline keyword inside the class. In other words, the code for an inline function is inserted directly into the code of the calling function, which can result in faster execution and less overhead compared to regular function calls.

Syntax of Inline Function

inline return_type function_name ( parameters )
 // inline function code

Code Implementation:

#include <iostream>

inline int max(int a, int b) {
  return (a > b) ? a : b;

int main() {
  int x = 10, y = 20;
  std::cout << "Max value is: " << max(x, y) << std::endl; // inline function call
  return 0;


Max value is: 20

In the above C++ program we use the inline function to find the maximum value.
In this example, the max() function is defined as an inline function using the inline keyword. When the max() function is called in the main() function, the code for the function is inserted directly into the code of the main() function at the point of call, rather than executing a separate function call.

The inline function max() takes two integer arguments, a and b, and returns the maximum value of the two. The ternary operator (a > b) ? a : b is used to determine the maximum value.

Macro Function

It is also known as the preprocessor directive. The #define keyword is used to define the macros. The preprocessor examines the program prior to program compilation, and if it detects macros, it replaces the macro with the macro definition.A macro function is a piece of code that performs a specific task and can be used repeatedly throughout a program.

Syntax of Macro Function

#define MACRO_NAME Macro_definition

Code Implementation:

#include <iostream>
using namespace std;

#define MAX(a, b) (((a) > (b)) ? (a) : (b))
int main(){
int x = 10;
int y = 20;
int result = MAX(x, y);
cout << "Maximum value is "<<result << endl;
return 0;


Maximum value is 20

In the above C++ program we have to use the macro function to find the maximum value. In this example, the macro function is called MAX and it takes two arguments, a and b. It uses a conditional operator to check whether a is greater than b. If a is greater, the function returns a, otherwise, it returns b.

Difference between Macro and Inline Fnction.

Here we have the difference between macro and inline functions.

Macro Function Inline Function
Macro function is a preprocessor directive that replaces a particular expression with a code segment during the preprocessing stage. Inline function is a keyword in C++ that requests the compiler to replace the function call statement with the corresponding function code during the compilation stage.
The macro function is defined using the #define directive. Whereas the inline function is defined by the inline keyword.
The code segment of a macro function is not type-checked, so it can lead to unexpected behavior if not used carefully. The code segment of an inline function is type-checked and the compiler ensures that the code is executed in a type-safe manner.
Macro functions are usually faster than inline functions as they are substituted during the preprocessing stage itself. Inline functions are slower than macro functions as the compiler needs to perform additional checks and optimizations during the compilation stage.
Macro functions can be used to perform simple text replacements or to define constants. Inline functions are used to reduce the function call overhead and improve performance by avoiding stack frame creation and destruction.
The arguments are evaluated every time whenever the macro is used in the program While in inline the argument are evaluated only once
Macro is also used in competitive programming While inline is not used in a competitive program
Macro is terminated by a new line While inline is terminated by the curly brace at the end
Example: #define MAX(x,y) ((x) > (y) ? (x) : (y)) Example: inline int max(int x, int y) { return x > y ? x : y; }

So these are the main difference between macro and inline functions.

In conclusion, Macros and Inline Functions are both powerful tools in the developer’s arsenal, serving different purposes in code optimization and performance improvement. Macros are preprocessor directives that perform textual substitution, offering efficiency but with limitations concerning type safety and debugging. Inline Functions, on the other hand, are actual function calls that can provide similar performance benefits while retaining type safety and debugging capabilities. By understanding the differences between Macros and Inline Functions, developers can make informed decisions and strike the right balance between performance and maintainability, leading to efficient and maintainable codebases.

Frequently Asked Questions(FAQs)

Here are some FAQs:

Q1. What is the difference between inline and macro functions?
Ans: The main difference between inline and macro functions is that inline functions are parsed by the compiler, whereas macros in a program are expanded by the preprocessor. The keyword "inline" is used to define an inline function, whereas "#define" is used to define a macro.

Q2. When should I use inline functions?
Ans: Inline functions are commonly used when the function definitions are short and the functions are called multiple times in a program. Using inline functions saves time by transferring program control from the calling function to the definition of the called function.

Q3. When should I use macro functions?
Ans: Macros are used for short operations and to avoid the overhead of function calls. It can be used if a short operation is repeated in a program. When the same block of code must be executed multiple times, function-like macros can be helpful.

Q4. Can inline and macro functions be used together?
Ans: Yes, inline and macro functions can be used together in C++ programs.

5. When should I use Inline Functions over Macros?
Use Inline Functions when you need the benefits of function call optimization without sacrificing type safety and debugging capabilities. Inline Functions are suitable for more complex logic and situations where code readability and maintainability are important considerations.

6. Can I use Macros and Inline Functions together?
Yes, you can use Macros and Inline Functions together in your codebase. Macros are typically used for simple operations, while Inline Functions can handle more complex tasks, allowing you to strike a balance between performance and maintainability.

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