Write a Dynamic Memory Allocator
Introduction
Dynamic memory allocation
Design a dynamic memory allocator
Implement a dynamic memory allocator
Memory allocation summary
Next Steps

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About this Learning Path

Skill level:  Introductory
Reading time:  2 hrs
Last updated:  02 Jul 2026
Skill level:
  Introductory
Reading time:
  2 hrs
Last updated:
  02 Jul 2026
Author:David Spickett, Arm
Arm IP:Cortex-A Neoverse
Tags: Performance and Architecture Linux C Runbook
Author:
  • David Spickett, Arm
Arm IP:
Cortex-A Neoverse
Tags:
Performance and Architecture Linux C Runbook

Who is this for?

This is an introductory topic for software developers learning about dynamic memory allocation for the first time, and who may have used malloc and free in C programming. It also provides a starting point to explore more advanced memory allocation topics.

What will you learn?

Upon completion of this Learning Path, you will be able to:

  • Explain how dynamic memory allocation and the C heap works
  • Write a simple dynamic memory allocator
  • Explain some of the risks of heap allocation in general

Prerequisites

Before starting, you will need the following:

  • Familiarity with C programming, with a good understanding of pointers.
  • A Linux machine to run the example code.

Summary

AI-assisted

This summary was drafted with an approved AI-assisted workflow and reviewed by Arm contributors before publication. Human technical review remains part of the process so the final page reflects engineering rigor, accuracy, and Arm editorial standards.

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You’ll design and implement a minimal dynamic memory allocator in C on Linux, showing how heap-style allocation works behind familiar interfaces. First, you’ll define the behavior of simple_malloc and simple_free, implement them in a small project with heap.c and heap.h, and exercise them from a provided test program. Then, you’ll contrast dynamic and static allocation, describe failure behavior, and explore practical trade-offs of a simple allocator. You’ll build and run the code, observe allocations and frees in action, and reason about basic risks and limitations of heap usage when integrating allocation into real programs.

Frequently asked questions

AI-assisted

These FAQs were drafted with an approved AI-assisted workflow and reviewed by Arm contributors before publication. Human technical review remains part of the process so the final page reflects engineering rigor, accuracy, and Arm editorial standards.

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Which files do I edit to implement the allocator?
Put the implementation in heap.c and the declarations in heap.h. The test program that calls your functions is in main.c, and CMakeLists.txt configures the build.
How do I confirm the test program calls my `simple_malloc` and `simple_free`?
Check that main.c includes heap.h and uses simple_malloc and simple_free. You can also add temporary logging or assertions in heap.c to verify the call flow during a test run.
What should I check if `simple_malloc` returns `NULL` for a small request?
Verify the requested size and confirm your allocator is initialized before the first request. Ensure your implementation handles allocation failure paths correctly and that the test code checks for NULL before using the returned pointer.
Do I need to replace the C library `malloc` and `free`?
No. You’ll use separate functions named simple_malloc and simple_free and won’t replace the C library allocator.
How can I sanity-check that `simple_free` works before moving on?
Run sequences that allocate, free, and then allocate again to see if subsequent requests succeed without errors. Add basic checks or prints in main.c and heap.c to confirm that block metadata and returned pointers behave as expected.
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