Macros and Inline Functions

Macros and inline functions help optimize code by reducing function call overhead.

In this lesson, you will learn:

• How to define and use macros.
• The benefits of inline functions over macros.
• How macros and inline functions improve performance.

What is a Macro?

A macro is a preprocessor directive that replaces code before compilation.

Example:

#define SQUARE(x) (x * x)

Now, SQUARE(5) is replaced with (5 * 5) during compilation.

Example: Using Macros

This program demonstrates how to use a macro for calculations.

#include <stdio.h>

#define SQUARE(x) (x * x)

int main() {
    int num = 4;
    printf("Square of %d is %d\n", num, SQUARE(num));
    return 0;
}

Limitations of Macros

Macros do not perform type checking and may cause unexpected results.

Example issue:

#define MULTIPLY(x, y) x * y

Calling MULTIPLY(2 + 3, 4) expands to 2 + 3 * 4, leading to incorrect results.

Introducing Inline Functions

Inline functions provide an alternative to macros while maintaining type safety.

Syntax:

inline int square(int x) { return x * x; }

They reduce function call overhead but ensure proper type checking.

Example: Using Inline Functions

This program demonstrates an inline function replacing a macro.

#include <stdio.h>

inline int square(int x) { return x * x; }

int main() {
    int num = 4;
    printf("Square of %d is %d\n", num, square(num));
    return 0;
}

Advantages of Inline Functions

Inline functions offer several benefits over macros:

• Type safety.
• Better debugging (they appear in stack traces).
• No unexpected expansion errors.

When to Use Macros vs Inline Functions

Use macros when:

• Defining simple constants.
• Performing minor text replacements.

Use inline functions when:

• Performing complex operations.
• Ensuring type safety.

Summary

In this lesson, you learned:

• How to define and use macros.
• The limitations of macros.
• How inline functions provide a safer alternative.

Next, we will explore conditional compilation!