C Structures and Dynamic Memory

📌 C Structures and Dynamic Memory Allocation

Dynamic memory allocation can also be applied to structures, allowing flexible creation of objects at runtime.
This is useful when the number of elements is unknown during compile time.

✅ Basic Example: Allocating Memory for a Struct

🧠 Using `->` Operator

When accessing structure members via pointer:

Operator	Usage
`.`	Access using structure variable
`->`	Access using structure pointer

Example:

📌 Dynamically Allocating an Array of Structs

#include <stdio.h>

#include <stdlib.h>

struct Employee {
char name[30];
float salary;
};int main() {
int n;
struct Employee *emp;

printf(“Enter number of employees: “);
scanf(“%d”, &n);

emp = (struct Employee *)malloc(n * sizeof(struct Employee));

if (emp == NULL) {
printf(“Memory allocation failed!\n”);
return 1;
}

for (int i = 0; i < n; i++) {
printf(“\nEnter name and salary for employee %d: “, i + 1);
scanf(“%s %f”, emp[i].name, &emp[i].salary);
}

printf(“\nEmployee Details:\n”);
for (int i = 0; i < n; i++) {
printf(“%s – %.2f\n”, emp[i].name, emp[i].salary);
}

free(emp);
return 0;
}

🔁 Using `realloc()` to Expand Struct Memory

Example:

🚨 Struct with Pointer Members (Deep Copy Required)

Sometimes a struct contains pointer members; then you must allocate memory inside the struct too.

🧹 Memory Cleanup Rule

If a struct contains dynamic memory pointers:

📝 Summary Table

Concept	Example
Allocate struct memory	`ptr = malloc(sizeof(struct MyStruct));`
Access data	`ptr->member`
Allocate array of structs	`malloc(n * sizeof(struct MyStruct))`
Resize struct array	`realloc(ptr, newSize)`
Free memory	`free(ptr);` (and internal pointers if any)

C Structures and Dynamic Memory