Dynamic Memory

What you'll walk away with

Explain the C language and runtime behavior of Dynamic Memory
Test normal, boundary, invalid, and failure cases
Use warnings and sanitizers to write safer C

Allocation can fail and every successful allocation needs one clear owner and one matching release.

Build a Complete Mental Model

Dynamic allocation requires control of size overflow, allocation failure, initialization, ownership transfer, exactly-one free, and use-after-free. Prefer `sizeof *ptr`, checked size arithmetic, and a single cleanup path.

Apply It in Real C

Allocate a calloc array from a user count and test failure, zero or excessive counts, normal use, and cleanup under AddressSanitizer.

After This Lesson

Explain the contract and undefined-behavior risk of Dynamic Memory
Build with no compiler warnings
Run a boundary or failure case under a sanitizer

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

int main(void) {
    size_t count = 5;
    int *values = calloc(count, sizeof *values);
    if (values == NULL) return EXIT_FAILURE;

    for (size_t i = 0; i < count; ++i) values[i] = (int)(i * 10);
    for (size_t i = 0; i < count; ++i) printf("%d%c", values[i], i + 1 == count ? '\n' : ' ');

    free(values);
    values = NULL;
    return EXIT_SUCCESS;
}

You should see

0 10 20 30 40

Try It Yourself

Allocate a calloc array from a user count and test failure, zero or excessive counts, normal use, and cleanup under AddressSanitizer.

Memory and Safety Warning

Unchecked allocation, size-multiplication overflow, and using a pointer after free are critical memory defects.

SEI CERT C Coding Standard — Carnegie Mellon SEI

Easy traps

Unchecked allocation, size-multiplication overflow, and using a pointer after free are critical memory defects.
Assuming one correct output proves bounds, lifetime, overflow, and ownership are all correct.

Hands-on Exercise

Allocate a calloc array from a user count and test failure, zero or excessive counts, normal use, and cleanup under AddressSanitizer.

You'll know it worked when: 0 10 20 30 40