Custom C Memory Allocator

Tru Bui

A lightweight malloc/free implementation written in C supporting block splitting, coalescing, boundary tags, segregated free lists, and LD_PRELOAD interposition. Designed to replace glibc's allocator at runtime for real-world testing.

Key Features

• Segregated free lists
• Boundary tags with left/right block tracking
• Coalescing and block splitting
• Thread-safe allocator (global mutex)
• OS chunk growth using sbrk()
• Implements malloc, free, calloc, realloc
• Override glibc using LD_PRELOAD

Usage

$ gcc -shared -fPIC -o libmymalloc.so myMalloc_sharedlib.c -ldl -pthread
$ LD_PRELOAD=./libmymalloc.so /bin/echo hello
$ LD_PRELOAD=./libmymalloc.so ls -l
    

Technologies & Concepts

• Heap management and memory layout
• Segregated free lists
• Boundary tag coalescing
• Pointer arithmetic & metadata layout
• Dynamic linking & LD_PRELOAD
• Thread safety & mutex locking
• Low-level system calls (sbrk(), write())

Contact me for source code