The latest articles on DEV Community by Alessio Fiorito (@fioritoalessio). https://dev.to/fioritoalessio https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F3795618%2F7cf97bdc-bbbb-4718-a19f-be90b699b500.png https://dev.to/fioritoalessio en Alessio Fiorito Thu, 26 Feb 2026 23:52:54 +0000 https://dev.to/fioritoalessio/my-own-memory-allocator-a-thread-safe-efficient-implementation-of-malloc-calloc-realloc-and-c4o https://dev.to/fioritoalessio/my-own-memory-allocator-a-thread-safe-efficient-implementation-of-malloc-calloc-realloc-and-c4o <p>Hey everyone,</p> <p>I decided to code my own memory allocator from scratch as a shared library I can actually use in my other projects. I thought it would be a cool way to understand what happens under the hood of malloc, calloc, realloc and free and build a reusable tool in the process.</p> <p>I tried my best to create an efficient, POSIX-compliant, and thread-safe library. Here is what i use</p> <ul> <li>Direct kernel mapping (mmap / munmap)</li> <li>Segregated free lists (O(1) search time)</li> <li>Boundary tags (header and footer) with O(1) coalescing</li> <li>Anonymous unions and structs inside the header for zero-overhead payloads</li> <li>Bitmasking to pack metadata into a single variable and not waste space</li> <li>POSIX Mutexes for thread safety</li> </ul> <p>I tried to think through the architecture by myself as much as possible. Since I mostly code solo projects for now, this is the first time I'm putting my code out there for people to actually see.</p> <p>If you have the time and motivation, I would greatly appreciate it if you could check out my GitHub repo and let me know thoughts on the code.</p> <p>github repo : <a href="https://github.com/Fiorito-Alessio/af_memory" rel="noopener noreferrer">https://github.com/Fiorito-Alessio/af_memory</a></p> <p>Thanks!</p> c programming codereview