My Malloc Implementation

A custom implementation of malloc, free, realloc, and calloc functions in C.

Overview

This project implements a memory allocator that manages dynamic memory allocation using:

• Free list data structure for efficient memory management
• Block coalescing to reduce fragmentation
• Thread-safe operations using pthread mutex
• Configurable arena size and number of free lists
• Optional relative pointer support

Features

• Custom Memory Management: Implements my_malloc(), my_free(), my_realloc(), and my_calloc()
• Free List Organization: Uses multiple free lists for different block sizes
• Memory Coalescing: Automatically merges adjacent free blocks
• Thread Safety: Protected with mutex locks for concurrent access
• Debug Support: Built-in debugging and validation features
• Configurable Parameters: Customizable arena size and list count

Configuration

Compile-time Options

• ARENA_SIZE: Size of memory arena (default: 4096 bytes)
• N_LISTS: Number of free lists (default: 59)
• RELATIVE_POINTERS: Enable relative pointer support (default: true)

Environment Variables

• MALLOC_DEBUG_COLOR: Enable colored debug output

Building

# Build with default settings
make

# Build with custom arena size
make CFLAGS="-DARENA_SIZE=8192"

# Build with debug information
make debug

# Clean build files
make clean

Usage

#include "myMalloc.h"

int main() {
    // Allocate memory
    void *ptr = my_malloc(100);
    
    // Reallocate
    ptr = my_realloc(ptr, 200);
    
    // Free memory
    my_free(ptr);
    
    return 0;
}

Project Structure

• myMalloc.h - Header file with function declarations and data structures
• myMalloc.c - Implementation of memory allocation functions
• Makefile - Build configuration
• README.md - This documentation

Implementation Details

Data Structures

• Header Structure: Contains metadata for each memory block including size, allocation state, and free list pointers
• Free Lists: Array of sentinel nodes organizing free blocks by size
• Fence Posts: Special markers to prevent coalescing across chunk boundaries

Memory Layout

[Header][User Data...]

Allocation States

• UNALLOCATED: Block is free and available
• ALLOCATED: Block is in use
• FENCEPOST: Special boundary marker

Testing

Run the allocator with various programs to test functionality:

# Test basic allocation
./test_program

# Test with debugging enabled
MALLOC_DEBUG_COLOR=1 ./test_program

Performance Considerations

• Free list organization minimizes search time for appropriately sized blocks
• Immediate coalescing reduces external fragmentation
• Mutex protection ensures thread safety but may impact performance in highly concurrent scenarios

License

This project is for educational purposes.