Macros

Introduction

Macros are preprocessor text replacements — object-like (#define MAX 100) and function-like (#define SQR(x) ((x)*(x))).

Understanding the topic

Parentheses Wrap parameters and whole expression — avoid SQR(x+1) bugs.

vs inline functions Macros have no type checking; functions are safer.

• Parentheses — Wrap parameters and whole expression — avoid SQR(x+1) bugs.
• vs inline functions — Macros have no type checking; functions are safer.

Step-by-step explanation

1. Parentheses — Wrap parameters and whole expression — avoid SQR(x+1) bugs.
2. vs inline functions — Macros have no type checking; functions are safer.

Informative example

Example program:

#include <stdio.h>
#define SQR(x) ((x) * (x))

int main(void) {
    printf("%d\n", SQR(3 + 2));
    return 0;
}

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Execution workflow

Best practices

• Enable warnings: gcc -Wall -Wextra -std=c11 source.c -o app
• Give every variable a defined value before it is read.
• Stay inside array bounds — C will not stop you from over-running a buffer.

Common mistakes

• Multiple evaluation of macro arguments
• Missing parentheses in macro body

Hands-on exercise

Practice problems:

• MAX macro for two values
• DEBUG macro with #ifdef

Summary

Macros in C — Text substitution — constants and function-like macros.