Linked List-based Malloc

How it works

This is a simple implementation of malloc() and free(). It uses a first fit approach, backed by a linked list. That is, whenever free() is called, it stores the newly freed memory fragments in a linked list sorted by memory address and merges fragments which are adjacent in memory. Then when malloc() is called, it first scans this list for an available memory fragment. If none is found, it issues a request to the kernel to allocate another piece of memory for it.

Building and running

The static object (.so) library can be built simply by running

make

There are no external dependencies. Running make produces libmalloc.so, which can be used in another process by executing e.g.

env LD_PRELOAD="./libmalloc.so" ls

Replace ls with the command you want to run. Alternately, you can use your libmalloc.so for everything by executing

export LD_PRELOAD="/path/to/libmalloc.so"

To switch back to the standard library, issue

export LD_PRELOAD=""

Testing

A test script, test.sh, has been provided. This script simply runs a unit test with the custom malloc library preloaded, as well as ls --color=auto. The script can be easily modified to test other commands.