C++ Memory Management E-Book

Patrice Roy

• Herausgeber: Packt Publishing
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Veröffentlichungsjahr: 2025

Beschreibung

C++ programmers often face challenges in allocating and managing memory efficiently, especially given the diverse needs of real-time systems, embedded systems, games, and conventional desktop applications. This book offers a targeted approach to address the unique memory constraints of each domain.
Written by an ISO C++ Standards Committee member, Patrice Roy, this guide covers fundamental concepts of object lifetime and memory organization to help you write simpler and safer programs. You’ll learn how to control memory allocation mechanisms, create custom containers and allocators, and adapt allocation operators to suit your specific requirements, making your programs smaller, faster, safer, and more predictable.
Starting with core principles of memory management, this book introduces modern facilities that simplify your work and then dives into memory management mechanics, building solutions for specific application needs, and measuring their impact on your program’s behavior.
By the end of this book, you’ll be able to write secure programs that handle memory optimally for your application domain. You will also have a strong grasp of both high-level abstractions for safer programs and low-level abstractions that allow detailed customization.

Leseprobe

C++ Memory Management

Write leaner and safer C++ code using proven memory-management techniques

Patrice Roy

C++ Memory Management

Copyright © 2025 Packt Publishing

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First published: March 2025

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This book was written with love, and I was fortunate to write it from a loving home with the encouragement of my wife, Isabelle (Za), and my children, Marguerite, Calypso, Amandine, Viktor, and Ludo. Oh, and lots of animals.

My participation in the ISO C++ Standards Committee has allowed me to get a deeper understanding of the workings of the amazing language that is C++. There are too many to thank for this, but I will at least mention Michael Wong, who invited me to participate in this enlightening adventure; Jon Kalb, who made it possible for me to meet these fine folks and gave me an opportunity to teach to a wider audience; and, of course, Bjarne Stroustrup, who gave us this language, which has been my primary tool for decades now. If you enjoy this book, know that they are indirectly responsible for it too.

– Patrice Roy

Foreword

Back in 2014, when Patrice Roy first joined our Canadian C++ standardization delegation team, I noticed something distinctive about his approach. He had this remarkable ability to untangle complex technical concepts and present them with striking clarity – a skill that would serve him well in crafting this book.

I’ve had the pleasure of collaborating with Patrice within the C++ standardization community since 2014, during which time he has contributed to ISO C++, CPPCON, and my SG14 group actively. His expertise and ability to clearly articulate complex technical concepts are evident throughout this work. This book isn’t merely a collection of rules; it’s an exploration of the core principles governing how C++ interacts with memory. From the foundational definition of an “object” to the intricacies of pointers and references, Patrice meticulously guides readers through the essential building blocks. He tackles challenging topics such as object lifetime, memory alignment, and the potential pitfalls of undefined behavior with clarity and precision.

Memory management lies at the core of modern C++ programming, yet it remains one of the most challenging areas to master. When Patrice approached me about this book, I immediately knew he was the perfect person to tackle such a vital topic. Having worked closely with Patrice for years, I’ve witnessed his exceptional ability to distill complex ideas into accessible, actionable knowledge. His technical expertise, coupled with his passion for teaching, sets him apart as a thought leader and educator in the C++ world. He is also one of the most genuine, kind, and honest people I have ever met.

This book, C++ Memory Management, is a testament to Patrice’s passion for dissecting complex topics and presenting them in an accessible way. It’s not just a dry recitation of rules and best practices; it’s a journey into the very heart of how C++ interacts with memory. From the fundamental definition of an “object” – a concept often taken for granted but surprisingly nuanced – to the often-misunderstood relationship between pointers and references, Patrice guides you through the essential building blocks. He doesn’t shy away from the tricky bits either, tackling the thorny issues of object lifetime, alignment, padding, and the ever-present danger of memory leaks.

This book reflects Patrice’s gift for progressive enlightenment. He begins with fundamental concepts – what exactly is an object in C++? How do pointers and references truly differ? These seemingly basic questions have nuanced answers that impact how we write code. From there, he ventures into trickier territory: object lifetime, alignment requirements, padding bytes, and the eternal challenge of preventing memory leaks.

Having spent years working on C++ atomics and memory models, I especially appreciate how the book builds understanding from first principles. Chapter 1 lays crucial groundwork for objects and memory representation. Chapter 2 bravely tackles undefined behavior and other pitfalls that can trap even experienced developers. This mirrors my own experience implementing transactional memory in C++ – understanding edge cases is vital.

As someone who has spent over two decades working on C++ compilers, language design, safety, AI, and particularly parallel computing and memory models, I appreciate the careful balance this book strikes between practical guidance and theoretical foundations. The progression from fundamental concepts in Chapter 1 through increasingly sophisticated memory management techniques mirrors the journey that many C++ developers must take.

I have had the privilege of working with Patrice for years, and I can confidently say that his approach to teaching and writing reflects the traits of a seasoned expert who deeply understands both the intricacies of C++ and the challenges faced by those who wield it. With his clear explanations and practical insights, this book is not just about memory management – it’s about writing better, safer, and more expressive C++ at every level of abstraction.

What sets this book apart is how it builds knowledge methodically, layer by layer, always connecting low-level details to high-level design principles. The sections on casts and const-correctness in Chapter 3 go far beyond syntax, illustrating how to express intent clearly in code and leverage the type system as a safety net. Chapter 4 delves into destructors and the RAII idiom, showcasing why C++ remains one of the most powerful tools for managing resources, allowing developers to write code that is both robust and clean.

The book’s treatment of smart pointers and RAII in later chapters reflects modern C++ at its finest – showing how we can harness the type system and object lifetime semantics to write code that is both safer and more elegant. This exemplifies the philosophy that has guided my work chairing various C++ standardization groups: that C++ should offer powerful abstractions while still giving developers precise control when they need it.

As a long-time contributor to the evolution of C++ standards and a leader in the development of parallel and heterogeneous programming models, my own journey has revolved around navigating the delicate balance between high-level abstractions and low-level optimizations. Whether working on high-performance computing (HPC) systems, pushing the boundaries of AI/ML frameworks, or designing robust programming models for safety-critical systems, I’ve often found myself returning to the fundamental questions: How do we manage resources efficiently? and How do we write code that is both powerful and maintainable?

Whether you’re a student learning C++, a professional developer looking to deepen your expertise, or an experienced programmer wanting to better understand the language’s memory model, this book is an invaluable resource. Patrice has created something special here – a thorough yet approachable guide to one of C++’s most important topics.

This book is not just a technical manual – it is a conversation with a mentor. I consider Patrice to also be my mentor. Patrice writes with the voice of someone who has navigated the sharp edges of C++ and emerged with a deep respect for its potential. His examples are not contrived; they are drawn from the real world.

So, dive in. Embrace the journey. And let Patrice’s expertise guide you to new heights in your C++ mastery.

– Michael Wong

Distinguished Engineer, ISO C++ Standards Founding Directions Group Chair, C++ Foundation Founding Director, Chair of SG14 (Games Dev/Low Latency/Financial, Embedded), SG19 (Machine Learning), Editor Concurrency TS2, Transactional Memory TS1/TS2, Canada’s All Programming Languages (SC22) and Automotive Functional Safety for self-driving cars (TC22/SC32) Chair

Contributors

About the author

Patrice Roy has been playing with C++ professionally, for pleasure, or (mostly) both for over 30 years. After a few years doing R&D and working on military flight simulators, he moved on to academics and has taught computer science since 1998. Since 2005, he has been involved more specifically in helping graduate students and professionals from the fields of real-time systems and game programming develop the skills they need to face today’s challenges.

Patrice has been a participating member of the ISO C++ Standards Committee since late 2014. He has five children, and his wife ensures that their house is home to a continuously changing number of cats, dogs, birds, and other animals.

About the reviewers

Dr. Martin Reddy is an IEEE fellow, an AAIA fellow, and an ACM Distinguished Engineer. He has published over 40 professional articles, 10 patents, and 2 books, including API Design for C++. Dr. Reddy was co-founder and CTO of the AI technology company PullString, which was acquired by Apple in 2019. At Apple, he was a software architect and designed major components of the Siri virtual assistant. Martin also spent 6 years at Pixar Animation Studios where he worked on the Academy Award-winning films Finding Nemo, The Incredibles, Ratatouille, and Wall-E. Before that, Dr. Reddy worked for 5 years at SRI International on distributed 3D terrain visualization technologies.

Kevin Carpenter, an experienced software engineer, excels in crafting high-availability C++ solutions for Linux and Windows, with expertise in transaction software, financial modeling, and system integration. As a lead project engineer, he ensures secure, high-speed credit card transactions. In his prior position, he played a lead role in developing an interest rate risk model for large credit unions, enhancing legacy code, and optimizing ERP data integration.

Kevin actively engages in the C++ community, volunteering at conferences such as ACCU, CppCon, C++ on Sea, and SwiftCraft, where he holds key positions such as speaker liaison and volunteer coordinator/chair. His diverse contributions to the C++ community showcase his commitment to excellence and drive for collaborative growth, leaving a lasting impact in the tech world.

Faezeh Sadat Zolfaghari began her journey into technology and robotics in late elementary school, driven by her passion for innovation and problem-solving. In middle school, she joined an elite national program for C++ programming, completing its 5-year curriculum as the top graduate among only 5 final participants out of 40. She then pursued a degree in computer science with a focus on cybersecurity. Since graduating, she has been working as a software engineer. Her curiosity spans areas such as biology, neuroscience, and robotics, inspiring her to explore the intersection of computing and interdisciplinary research. Her interests include algorithm optimization, HPC, and mathematics, all aimed at solving complex challenges.

Table of Contents

Preface

Part 1: Memory in C++

1

Objects, Pointers, and References

Technical requirements

Representation of memory in C++

Objects, pointers, and references

Understanding the fundamental properties of objects

Object lifetime

Object size, alignment, and padding

Copy and movement

Arrays

Summary

2

Things to Be Careful With

Different kinds of evil

Ill-formed, no diagnostic required

Undefined behavior

Implementation-defined behavior

Unspecified behavior (not documented)

The ODR

Erroneous behavior

Pointers

Uses of pointer arithmetic within an array

Pointer interconvertibility

Uses of pointer arithmetic within an object

Type punning

Type punning through members of a union

The intptr_t and uintptr_t types

The std::memcpy() function

The special cases of char*, unsigned char*, and std::byte*

The std::start_lifetime_as<T>() function

Summary

3

Casts and cv-qualifications

Technical requirements

What is a cast?

Safety in the type system – cv-qualifications

The C++ casts

Your best friend (most of the time) – static_cast

A sign something’s wrong – dynamic_cast

Playing tricks with safety – const_cast

“Believe me, compiler” – reinterpret_cast

I know the bits are right – bit_cast

Somewhat unrelated, but still – duration_cast

The reviled one – the C cast

Summary

Part 2: Implicit Memory Management Techniques

4

Using Destructors

Technical requirements

On destructors: a short recap

Managing resources

Exception handling… or not?

The RAII idiom

RAII and C++’s special member functions

Some pitfalls

Destructors should not throw

Know thy destruction order

Standard resource management automation tools

unique_ptr<T> and shared_ptr<T>

lock_guard and scoped_lock

stream objects

vector<T> and other containers

Summary

5

Using Standard Smart Pointers

Technical requirements

The standard smart pointers

On the exposition of intent through function signatures

Type unique_ptr

Handling objects

Handling arrays

Custom deleters

make_unique

Types shared_ptr and weak_ptr

Usefulness and costs

make_shared()

What about weak_ptr?

When to use raw pointers

Summary

6

Writing Smart Pointers

Technical requirements

Ownership semantics

Writing your own (naïve) unique_ptr

Type signature

Special member functions

Pointer-like functions

Writing your own (naïve) shared_ptr

A few words on make_shared()

Writing a policy-based duplicating pointer

Detection through interfaces

Detection through traits

Detection through concepts

Some not-so-smart yet useful smart pointers

A non_null_ptr type

An observer_ptr type

Summary

Part 3: Taking Control (of Memory Management Mechanisms)

7

Overloading Memory Allocation Operators

Why would one overload allocation functions?

Brief overview of the C language allocation functions

Overview of the C++ allocation operators

Global allocation operators

Non-throwing versions of the allocation operators

The most important operator new: placement new

Member versions of the allocation operators

Alignment-aware versions of the allocation operators

Destroying delete

Summary

8

Writing a Naïve Leak Detector

Technical requirements

The plan

A first implementation (that almost works)

The Accountant singleton class

Implementing the new and new[] operators

Implementing the delete and delete[] operators

Visualizing it all

Identifying (and fixing) the problems

Revisiting our implementation (and lessons learned)

Summary

9

Atypical Allocation Mechanisms

Technical requirements

Placement new and memory-mapped hardware

Simplifying nothrow new usage

Out-of-memory situations and new_handler

Standard C++ and exotic memory

A fictional shared memory API

A handmade user code example

A standard-looking user code equivalent

Summary

10

Arena-Based Memory Management and Other Optimizations

Technical requirements

Arena-based memory management

Specific example – size-based implementation

Generalizing to SizeBasedArena<T,N>

When parameters change

Chunked pools

Summary

11

Deferred Reclamation

Technical requirements

What do we mean by deferred reclamation?

Reclamation (without finalization) at the end of the program

Reclamation and finalization at the end of the program

Reclamation and finalization at the end of the scope

Summary

Part 4: Writing Generic Containers (and a Bit More)

12

Writing Generic Containers with Explicit Memory Management

Technical requirements

Writing your own vector<T> alternative

Representational choices for a container of contiguous elements

The implementation of Vector<T>

Writing your own forward_list<T> alternative

Representational choices for a node-based container

The implementation of ForwardList<T>

Better memory management

A more efficient Vector<T>

Using low-level standard facilities

Const or reference members and std::launder()

Summary

13

Writing Generic Containers with Implicit Memory Management

Technical requirements

Why explicit memory management complicates our implementation

Implicit memory management with a smart pointer

Impact on the naïve Vector<T> implementation

Impact on the sophisticated Vector<T> implementation

Consequences of this redesign

Generalizing to ForwardList<T>?

Attempt - making each node responsible for its successor

Attempt: making the head pointer responsible for the other nodes

Summary

14

Writing Generic Containers with Allocator Support

Technical requirements

Why allocators?

Traditional allocators

Before C++11

Traditional allocators with contemporary standards

Managing traditional allocator lifetime

Irritants with traditional allocators

Polymorphic memory resource allocators

Nested allocators

Allocators and data collection

Upsides and costs

Summary

15

Contemporary Issues

Technical requirements

Starting object lifetime without constructors

Trivial relocation

Type-aware allocation and deallocation functions

Summary

Annexure

Things You Should Know

struct and class

std::size_t

The sizeof operator

Assertions

Undefined behavior

Type traits

The std::true_type and std::false_type traits

The std::conditional<B,T,F> trait

Algorithms

Functors (function objects) and lambdas

Friends

The decltype operator

Perfect forwarding

The singleton design pattern

Instantiation at program startup

Instantiation of the first call

The std::exchange() function

Index

Other Books You May Enjoy

Part 1: Memory in C++

In this part, we will develop a common vocabulary on some key aspects of the object model in C++. This includes a discussion of ideas such as what an object is, what a reference is, and how C++ represents memory; a look at some of the risky or delicate maneuvers we sometimes need to do when writing low-level code (and the consequences that stem from doing them inappropriately); and how to coerce the type system to our needs in ways that do not come back to harm us. The knowledge gathered in this part will serve as a basis from which later chapters will be built.

This part has the following chapters:

Chapter 1, Objects, Pointers, and ReferencesChapter 2, Things to Be Careful withChapter 3, Casts and cv-qualifications