How to Find Size of Dynamic Array in C?

In C, dynamic memory allocation allows us to manage memory resources during the execution of a program. It’s particularly useful when dealing with arrays where the size isn’t known at compile time. In this article, we will learn how to find the size of a dynamically allocated array in C.

Find Size of a Dynamically Allocated Array in C

When we dynamically allocate an array using the malloc, calloc, or realloc functions, the size of the array isn’t stored anywhere in memory. Therefore, there’s no direct way to find the size of a dynamically allocated array. To manage the size of a dynamically allocated array, we must keep track of the size separately.

C Program to Keep the Track of Dynamically Allocated Array

The below program demonstrates how we can keep track of the size of a dynamically allocated array in C.

C

// C program to illustrate how to keep track of dynamically
// allocated array
#include <stdio.h>
#include <stdlib.h>

int main()
{
    int size = 5; // size of the array
    int* arr = (int*)malloc(
        size * sizeof(int)); // dynamically allocated array

    // fill the array
    for (int i = 0; i < size; i++) {
        arr[i] = i;
    }

    // print the array
    for (int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }

    free(arr); // free the array to avoid memory leak

    return 0;
}

Output

0 1 2 3 4 

Note: In C, it’s generally recommended to use structures or linked lists when you need to keep track of the size of a dynamically allocated array during runtime. This provides more flexibility and control over the memory.