C malloc / free

C malloc / free – Dynamic Memory Allocation

In C, the malloc() function is used to allocate memory dynamically during runtime, and the free() function is used to release the allocated memory. These functions provide a way to manage memory efficiently in programs where the amount of memory needed is not known beforehand.

🔹 malloc() – Memory Allocation

The malloc() function allocates a block of memory of a specified size. If the memory is successfully allocated, it returns a pointer to the first byte of the memory block. If the allocation fails, it returns NULL.

📝 Example 1: Using malloc()

This example demonstrates how to allocate memory for an array of integers dynamically using malloc(), assign values to it, and then free the memory.

#include <stdio.h>
#include <stdlib.h>

int main() {
    int *arr;
    arr = (int *)malloc(5 * sizeof(int)); // Allocating memory for 5 integers

    if (arr == NULL) {
        printf("Memory allocation failed\n");
        return 1;
    }

    // Assigning values to the allocated memory
    for (int i = 0; i < 5; i++) {
        arr[i] = i + 1;
    }

    // Printing values
    for (int i = 0; i < 5; i++) {
        printf("arr[%d] = %d\n", i, arr[i]);
    }

    free(arr); // Freeing the allocated memory
    return 0;
}

🔹 free() - Memory Deallocation

The free() function is used to release previously allocated memory that is no longer needed. After calling free(), the pointer becomes invalid and should not be used again without being reassigned.

📝 Example 2: Using free()

This example demonstrates how to allocate memory using malloc() and then release it using free() after use.

#include <stdio.h>
#include <stdlib.h>

int main() {
    int *arr;
    arr = (int *)malloc(5 * sizeof(int)); // Allocating memory for 5 integers

    if (arr == NULL) {
        printf("Memory allocation failed\n");
        return 1;
    }

    // Assigning values to the allocated memory
    for (int i = 0; i < 5; i++) {
        arr[i] = i + 1;
    }

    // Printing values
    for (int i = 0; i < 5; i++) {
        printf("arr[%d] = %d\n", i, arr[i]);
    }

    free(arr); // Freeing the allocated memory
    printf("Memory has been freed.\n");

    return 0;
}

⚙️ Important Notes

• Always check if malloc() returns NULL to handle memory allocation failures.
• Never use a pointer after it has been freed. Doing so leads to undefined behavior.
• Using free() helps prevent memory leaks by deallocating memory that is no longer needed.

🎯 Recap

Dynamic memory allocation in C using malloc() and free() helps you manage memory more efficiently, particularly when working with large datasets or variable-sized structures. Always remember to release memory once it’s no longer needed to avoid memory leaks and ensure your program runs efficiently.