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C++26: std::format improvements (Part 2) -- Sandor Dargo

By Blog Staff | Sep 2, 2025 02:54 PM | Tags: None

In Part 1, we explored the improvements C++26 brings to std::format — from better to_string behavior to compile-time safety checks. In this part, we look at runtime formatting, defect fixes, and support for new types like std::filesystem::path.

C++26: std::format improvements (Part 2)

by Sandor Dargo

From the article:

Runtime format strings

P2216R3 brought quite some improvements to std::format, including compile-time checking for format strings. Sadly, in use cases where format strings were only available at runtime, users had to go with the type-erased formatting version, std::vformat:

std::vformat(str, std::make_format_args(42));

Using two different APIs is not a great user experience, moreover, std::vformat was designed to be used by formatting function writers and not by end users. In addition, you might run into undefined behaviour, detailed in the next section.

To overcome this situation, P2918R2 adds std::runtime_format so you can mark format strings that are only available at run-time. As such you can opt out of compile-time format strings checks. This makes the API cleaner and the user code will read better as it shows better the intentions.

CppCon 2025 Back to Basics: static, inline, const, and constexpr -- Andreas Fertig

By Blog Staff | Sep 1, 2025 12:54 PM | Tags: None

Registration is now open for CppCon 2025! The conference starts on September 13 and will be held in person in Aurora, CO. To whet your appetite for this year’s conference, we’re posting some upcoming talks that you will be able to attend this year. Here’s another CppCon future talk we hope you will enjoy – and register today for CppCon 2025!

Back to Basics: static, inline, const, and constexpr

Thursday, September 18 09:00 - 10:00 MDT

by Andreas Fertig

Summary of the talk:

C++ comes with a whole toolbox of keywords you can apply to types and functions. You think it's straightforward? My experience says otherwise. There are false-friends like static , which I often see misapplied.

In this talk, I will demystify those tricky little keywords. You'll learn what they really mean, how they behave in different contexts, and — most importantly — when to use them (and when not to). Think const, constexpr, consteval, constinit: yes, C++ has more flavors of constness than your local ice cream shop. We'll explore them all.

We'll go beyond syntax and dive into what's actually happening in the language.

While the talk includes some features from C++23, most of what we cover is rooted in C++11 or even classic C++98. We'll touch on important concepts like the One Definition Rule (ODR) and top-level qualifiers, giving you a deeper understanding of how these keywords shape your code.

After this session, you'll walk away knowing exactly where each keyword belongs. No more guesswork. Just the right keyword in the right place.

Andreas Fertig, CEO of Unique Code GmbH, is an experienced trainer and consultant for C++ for standards 11 to 23. Andreas is involved in the C++ standardization committee, developing the new standards. At international conferences, he presents how code can be written better. He publishes specialist articles, e.g., for iX magazine, and has published several textbooks on C++. With C++ Insights (https://cppinsights.io), Andreas has created an internationally recognized tool that enables users to look behind the scenes of C++ and thus understand constructs even better. Before training and consulting, he worked for Philips Medizin Systeme GmbH for ten years as a C++ software developer and architect focusing on embedded systems. You can find Andreas online at andreasfertig.com.

CppCon 2025 Welcome to v1.0 of the meta::[[verse]]! -- Inbal Levi

By Blog Staff | Aug 30, 2025 12:50 PM | Tags: None

Welcome to v1.0 of the meta::[[verse]]!

Wednesday, September 17 16:45 - 17:45 MDT

by Inbal Levi

Summary of the talk:

This talk will introduce what is (likely) the final version of the "Reflection" feature targeting C++26.

With a proposal to introduce reflection to C++26 (including the “std::meta” namespace) slated to be voted into the standard in June 2025, we can already start imagining a whole new world of possibilities.

In this session, we will dive into reflection and its transformative potential within our codebases. We will start with a brief history of "reflection" history. We'll continue with an introduction of utilities from the latest reflection proposal. Then, we delve deeper into practical applications and demonstrate solutions to problems that commonly use reflection and the power it holds. For the last part, we will explore the possibilities within “Reflection Libraries”. This includes both “traditional” libraries which provide functionality, and more “novel” approaches which reshape users’ code. We will look at examples of what such libraries can cover, and demonstrate potential directions the future holds. Last but not least, we will discuss how "Reflection" may impact the way we manage our codebases and the delivery process.

Join us as we traverse the meta::[[verse]]!

Inbal Levi is a Lead Software Engineer at Millennium (MPGC Services Ltd) with a passion for high performance, readability, compilers, language, and software design. She is an active member of the ISO C++ Standards Committee as Library Evolution Work Group Chair, and as the ISO C++ Israeli NB Chair. Inbal is also a director at ISO C++ Foundation and the Boost Foundation and puts effort into evolving both the local and international C++ communities, as an organizer of the CoreC++ conference and meetup group, and as the program chair of C++Now.

C++26: std::format improvement (Part 1) -- Sandor Dargo

By Blog Staff | Aug 29, 2025 02:54 PM | Tags: None

C++26 brings a series of improvements to std::format, continuing the work started in C++20 and refined in C++23. These changes improve formatting consistency, runtime safety, and user ergonomics. There are so many of these updates, that I decided to divide them into two articles.

C++26: std::format improvement (Part 1)

by Sandor Dargo

From the article:

Arithmetic overloads of std::to_string and std::to_wstring use std::format

P2587R3 by Victor Zverovich proposes replacing sprintf with std::format in the arithmetic overloads of std::to_string and std::to_wstring.

The motivation?

std::to_string has long been known to produce not-so-great and misleading results (differing from iostreams), especially with floating-point values. std::to_string uses the global C locale. In practice, it’s unlocalized. Also, it often places the decimal points to suboptimal places:
std::cout << std::to_string(-1e-7); // prints: -0.000000 
std::cout << std::to_string(0.42); // prints: 0.420000
These outputs are imprecise and often unnecessary. By leveraging std::format (and ultimately std::to_chars), we now get clearer, shorter representations. The representations of floating-point overloads become also unlocalized and use the shortest decimal representations.

As a result, the above outputs would change as follow:

    std::cout << std::to_string(-1e-7);  // prints: -1e-7
    std::cout << std::to_string(0.42); // prints: 0.42

CppCon 2025 Keynote: C++: Some Assembly Required -- Matt Godbolt

By Blog Staff | Aug 29, 2025 12:39 PM | Tags: None

C++: Some Assembly Required

Friday, September 19 16:15 - 18:00 MDT

by Matt Godbolt

Summary of the talk:

Join Matt in exploring how the C++ ecosystem has evolved through the interplay of intentional design and emergent collaboration. Standards committees craft language features and compiler teams implement them, but something amazing happens in the spaces between: tools appear, communities form, and solutions emerge that nobody quite planned for. What started as individual developers solving their own problems has grown into an interconnected ecosystem that shapes how we all write C++.

From documentation to testing, from build systems to package managers, we'll examine how the C++ community has assembled itself around shared pain points and accidental standards. Using examples and perhaps too many rainforest metaphors, this talk celebrates not just the language we've built, but the organic ecosystem that's grown up around it. Come discover why C++'s greatest strength might be that it's always required some assembly.
Presenters

Matt Godbolt is the creator of the Compiler Explorer website. He is passionate about writing efficient code. He has previously worked at a trading firm, on mobile apps at Google, run his own C++ tools company and spent more than a decade making console games. When he's not hacking on Compiler Explorer, Matt enjoys writing emulators for old 8-bit computer hardware.

CppCon 2025 Keynote: More Speed & Simplicity:Practical Data-Oriented Design in C++ -- Vittorio Romeo

By Blog Staff | Aug 28, 2025 12:32 PM | Tags: None

Keynote: More Speed & Simplicity:Practical Data-Oriented Design in C++

Thursday, September 18 10:30 - 12:00 MDT

by Vittorio Romeo

Summary of the talk:

Data-Oriented Design (DOD) presents a different way of thinking: prioritizing data layout not only unlocks significant performance gains via cache efficiency but can also lead to surprising simplicity in the code that actually processes the data.

This talk is a practical introduction for C++ developers familiar with OOP. Through a step-by-step refactoring of a conventional OOP design, we’ll both cover how data access patterns influence speed and how a data-first approach can clarify intent.

We’ll measure the performance impact with benchmarks and analyze how the refactored code, particularly the data processing loops, can become more direct and conceptually simpler.

Key techniques like Structure-of-Arrays (SoA) vs. Array-of-Structures (AoS) will be explained and benchmarked, considering their effects on both execution time and code clarity. We’ll pragmatically weigh the strengths (performance, simpler data logic) and weaknesses of DOD, highlighting how it can complement, not just replace, OOP.

We’ll also demonstrate that DOD doesn’t necessitate abandoning robust abstractions, showcasing C++ techniques for creating safe, expressive APIs that manage both complexity and performance.

Let’s learn how thinking “data-first” can make your C++ code faster and easier to reason about!

Vittorio Romeo (B.Sc. Computer Science, 9+ YoE at Bloomberg) works on mission-critical C++ infrastructure and provides Modern C++ training to hundreds of fellow employees. He began programming around the age of 8 and became a C++ enthusiast shortly after discovering the language. Vittorio created several open-source C++ libraries and games, published many video courses and tutorials, actively participates in the ISO C++ standardization process, and maintains the popular SFML library. He co-authored the acclaimed "Embracing Modern C++ Safely" book (published in January 2022) with J. Lakos, R. Khlebnikov, and A. Meredith. Vittorio is an active member of the C++ community with an ardent desire to share his knowledge and learn from others: he presented and offered workshops over 20 times at international C++ conferences (including CppCon, C++Now, ++it, ACCU, C++ On Sea, C++ Russia, and Meeting C++), covering topics of various nature. He also maintains a website with advanced C++ articles and a YouTube channel featuring well-received modern C++11/14 tutorials. Lastly, he's active on StackOverflow, taking great care in answering interesting C++ question (90k reputation). When he's not writing code, Vittorio enjoys weightlifting, playing volleyball, scuba diving, canyoning, gaming, and enjoying sci-fi content.

Boost version 1.89 released!

By Blog Staff | Aug 27, 2025 02:50 PM | Tags: None

Release 1.89 of the Boost C++ Libraries is now available.

One new library and updates to 28 more.

Bloom, configurable filters for probabilistic lookup: https://boost.org/libs/bloom

CppCon 2025 Keynote: Crafting the Code You Don’t Write: Sculpting SW in an AI World -- Daisy Hollman

By Blog Staff | Aug 26, 2025 12:27 PM | Tags: None

Crafting the Code You Don't Write: Sculpting Software in an AI World

Tuesday, September 16 10:30 - 12:00 MDT

by Daisy Hollman

Summary of the talk:

It’s shockingly uncontroversial to say that the fields of developer experience and developer productivity have changed more in the past six months than in the 25 years before that.

As part of the Claude Code team at Anthropic, I’ve had the privilege of witnessing the evolution of agentic coding from proof-of-concept experiments to nearly autonomous software engineers in just six months. In this keynote, I’ll share some of my experiences and learnings from that journey, talk about how LLMs work more generally, attempt some live demonstrations of the latest functionality, explore the future of agentic programming, and tie all of this back to what it means for your workflow as a software engineer.

When I agreed to give this talk earlier this year, there was some portion of the narrative that involved “why you should be using agents to accelerate your development process.” Since then, the world of software engineering has evolved such that the interesting question is no longer “why” but “how.” Like sculptors facing the invention of power tools, or painters around the invention of photography, we now live in a world where vast quantities of rough-draft code can be generated with a very low barrier to entry. How does the role of a software engineer evolve when AI can autonomously implement features from requirements? How do we build safety features into the power tools we’re chiseling away at our codebases with? What aspects of software craftsmanship become more important, not less, in an age of abundant code generation? And critically for the C++ community: how do we leverage these tools where correctness and performance are non-negotiable? The future isn’t about AI replacing programmers, but about a fundamental shift in how we think about software creation. And surprisingly, you might not miss the old way of doing things.

Dr. Daisy Hollman is a distinguished software engineer and programming language expert, known for her impactful contributions to the C++ standards committee since 2016. She has worked on C++ language and library design at Google, and more recently joined Anthropic, where she explores the intersection of programming languages and AI systems.

CppCon 2025 Keynote: Reflection: C++’s Decade-Defining Rocket Engine -- Herb Sutter

By Blog Staff | Aug 25, 2025 09:14 AM | Tags: None

Keynote: Reflection: C++’s Decade-Defining Rocket Engine

Wednesday, September 17 10:30 - 12:00 MDT

by Herb Sutter

Summary of the talk:

In June 2025, C++ crossed a Rubicon: it handed us the keys to its own machinery. For the first time, C++ can describe itself—and generate more. The first compile-time reflection features in draft C++26 mark the most transformative turning point in our language’s history by giving us the most powerful new engine for expressing efficient abstractions that C++ has ever had, and we’ll need the next decade to discover what this rocket can do.

This session is a high-velocity tour through what reflection enables today in C++26, and what it will enable next. We’ll start with live compiler demos (Godbolt, of course) to show how much the initial C++26 feature set can already do. Then we’ll jump a few years ahead, using Dan Katz’s Clang extensions and my own cppfront reflection implementation to preview future capabilities that could reshape not just C++, but the way we think about programming itself.

We’ll see how reflection can simplify C++’s future evolution by reducing the need for as many bespoke new language features, since many can now be expressed as reusable compile-time libraries—faster to design, easier to test, and portable from day one. We’ll even glimpse how it might solve a problem that has long eluded the entire software industry, in a way that benefits every language.

The point of this talk isn’t to immediately grok any given technique or example. The takeaway is bigger: to leave all of us dizzy from the sheer volume of different examples, asking again and again, “Wait, we can do that now?!”—to fire up our imaginations to discover and develop this enormous new frontier together, and chart the strange new worlds C++ reflection has just opened for us to explore.

Reflection has arrived, more is coming, and the frontier is open. Let’s go.

Herb is an author, designer of several Standard C++ features, and chair of the ISO C++ committee and the Standard C++ Foundation. His current interest is simplifying C++.

CppCon 2025 To Err is Human: Robust Error Handling in C++26 -- Sebastian Theophil

By Blog Staff | Aug 24, 2025 08:45 AM | Tags: None

To Err is Human: Robust Error Handling in C++26

Wednesday, September 17 15:15 - 16:15 MDT

by Sebastian Theophil

Summary of the talk:

Every program may encounter errors, some originating from internal bugs in the program, others coming from the environment the program is operating in. Ignoring all errors will make the program utterly unreliable, while treating every conceivable one introduces lots of extra complexity with little benefit. So which errors should you handle? And how should you handle them? This talk describes our proven approach to error handling so that you can write more reliable software with less effort.

C++23 and C++26 have seen several improvements to C++ error handling: std::stacktrace, std::expected, contracts and library hardening. We will cover these features as well and how to best use them in practice to catch more errors, report them and fix them.

Sebastian has been working at think-cell since its founding in 2002. In the last few years, among many other things, he has ported think-cell to run on macOS. He is also the maintainer of the typescripten project which lets programmers call JavaScript libraries from C++ code compiled to WebAssembly in a convenient and type-safe way. He enjoys leaving his desk from time to time to talk at international C++ conferences.