Custom Dynamic Memory Allocator in C

A user-space heap allocator implemented in C using mmap, supporting malloc and free with a linked-list free list and first-fit allocation strategy.

Overview

This project implements a simplified dynamic memory allocator to understand how heap management works internally.

Key features:

• Memory pool backed by mmap
• Linked-list free list
• First-fit allocation strategy
• Block splitting for efficient reuse
• Adjacent block coalescing to reduce fragmentation
• 8-byte memory alignment
• In-memory block metadata management

Architecture

Each block stores metadata in-band:

typedef struct Block {
    size_t size;
    int is_free;
    struct Block* next;
} Block;

Allocation flow:

1. Align requested size to 8 bytes\
2. Search free list (first-fit)\
3. Split block if oversized\
4. Return pointer past metadata

Free flow:

1. Mark block as free\
2. Coalesce with adjacent free block

Build & Run

gcc allocator.c -o allocator
./allocator

Concepts Demonstrated

• Virtual memory management (mmap)
• Manual heap management
• Fragmentation control
• Pointer arithmetic
• Memory alignment
• Low-level systems programming

Future Improvements

• Implement realloc / calloc
• Add boundary tags for bidirectional coalescing
• Add benchmarking vs glibc malloc
• Add thread safety