Introduction
Table of contents
In this portion of the assignment, you will be implementing your own memory allocator from scratch.
Compilation
To compile the code for this part:
cd ~/code/personal/hw-memory/mm_alloc
make
Skeleton
Code for this part can be found in the mm_alloc subdirectory of the hw-memory directory.
You will find a simple skeleton in mm_alloc.c. mm_alloc.h defines an interface with three functions: mm_malloc, mm_free, mm_realloc. You will need to implement these functions. Do not change the headers of any of these!
The given mm_test.c performs some sanity checks but is not an exhaustive test. We recommend you write some custom tests when testing locally by changing this file.
Background
The man pages for malloc and sbrk are excellent resources for this assignment. Note that you must use sbrk to allocate the heap region. You are NOT allowed to call the standard malloc/free/realloc functions.
You may want to refer back to the first part of the homework for information on how process memory works. In this part, you will be allocating blocks of memory in the mapped region of the heap and moving the break appropriately using the sbrk syscall. Initially the mapped region of the heap will have a size of 0.
Heap data structure
A simple memory allocator for the heap can be implemented using a linked list data structure. The elements of the linked list will be the allocated blocks of memory on the heap. To structure our data, each allocated block of memory will be preceded by a header containing metadata.
For each block, we include the following metadata:
prev, next
Pointers to metadata describing the adjacent blocks
free
Boolean describing whether or not this block is free
size
Allocated size of the block of memory
You might also consider using a flexible array member to serve as a pointer to the memory block.