Tag: C++

Yesterday’s talk video posted: Reflection — C++’s decade-defining rocket engine

My CppCon keynote video is now online. Thanks to Bash Films for turning around the keynotes in under 24 hours!

C++ has just reached a true watershed moment: Barely three months ago, at our Sofia meeting, static reflection became part of draft standard C++. This talk is entirely devoted to showing example after example of how it works in C++26 and planned extensions beyond that, and how it will dramatically alter the trajectory of C++ — and possibly also of other languages. Thanks again to Max Sagebaum for coming on stage and explaining automatic differentiation, including his world’s-first C++ (via cppfront) autodiff implementation using reflection!

I hope you enjoy the talk and live demos, and find it useful.

Here is a copy of the talk abstract…

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, Daveed Vandevoorde’s EDG 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.

New U.S. executive order on cybersecurity

The Biden administration just issued another executive order (EO) on hardening U.S. cybersecurity. This is all great stuff. (*) (**)

A lot of this EO is repeating the same things I urged in my essay nearly a year ago, “C++ safety — in context”… here’s a cut-and-paste of my “Call(s) to action” conclusion section I published back then, and I think you’ll see a heavy overlap with this week’s new EO…

Call(s) to action

As an industry generally, we must make a major improvement in programming language memory safety — and we will.

In C++ specifically, we should first target the four key safety categories that are our perennial empirical attack points (type, bounds, initialization, and lifetime safety), and drive vulnerabilities in these four areas down to the noise for new/updated C++ code — and we can.

But we must also recognize that programming language safety is not a silver bullet to achieve cybersecurity and software safety. It’s one battle (not even the biggest) in a long war: Whenever we harden one part of our systems and make that more expensive to attack, attackers always switch to the next slowest animal in the herd. Many of 2023’s worst data breaches did not involve malware, but were caused by inadequately stored credentials (e.g., Kubernetes Secrets on public GitHub repos), misconfigured servers (e.g., DarkBeam, Kid Security), lack of testing, supply chain vulnerabilities, social engineering, and other problems that are independent of programming languages. Apple’s white paper about 2023’s rise in cybercrime emphasizes improving the handling, not of program code, but of the data: “it’s imperative that organizations consider limiting the amount of personal data they store in readable format while making a greater effort to protect the sensitive consumer data that they do store [including by using] end-to-end [E2E] encryption.”

No matter what programming language we use, security hygiene is essential:

  • Do use your language’s static analyzers and sanitizers. Never pretend using static analyzers and sanitizers is unnecessary “because I’m using a safe language.” If you’re using C++, Go, or Rust, then use those languages’ supported analyzers and sanitizers. If you’re a manager, don’t allow your product to be shipped without using these tools. (Again: This doesn’t mean running all sanitizers all the time; some sanitizers conflict and so can’t be used at the same time, some are expensive and so should be used periodically, and some should be run only in testing and never in production including because their presence can create new security vulnerabilities.)
  • Do keep all your tools updated. Regular patching is not just for iOS and Windows, but also for your compilers, libraries, and IDEs.
  • Do secure your software supply chain. Do use package management for library dependencies. Do track a software bill of materials for your projects.
  • Don’t store secrets in code. (Or, for goodness’ sake, on GitHub!)
  • Do configure your servers correctly, especially public Internet-facing ones. (Turn authentication on! Change the default password!)
  • Do keep non-public data encrypted, both when at rest (on disk) and when in motion (ideally E2E… and oppose proposed legislation that tries to neuter E2E encryption with ‘backdoors only good guys will use’ because there’s no such thing).
  • Do keep investing long-term in keeping your threat modeling current, so that you can stay adaptive as your adversaries keep trying different attack methods.

We need to improve software security and software safety across the industry, especially by improving programming language safety in C and C++, and in C++ a 98% improvement in the four most common problem areas is achievable in the medium term. But if we focus on programming language safety alone, we may find ourselves fighting yesterday’s war and missing larger past and future security dangers that affect software written in any language.

Sadly, there are too many bad actors. For the foreseeable future, our software and data will continue to be under attack, written in any language and stored anywhere. But we can defend our programs and systems, and we will.

(*) My main disappointment is that some of the provisions have deadlines that are too far away. Specifically: Why would it take until 2030 to migrate to TLS 1.3? It’s not just more secure, it’s also faster and has been published for seven years already… maybe I’m just not aware enough of TLS 1.3 adoptability issues though, as I’m not a TLS expert.

(**) Here in the United States, we’ll have to see whether the incoming administration will continue this EO, or amend/replace/countermand it. In the United States, that’s a drawback of using an EO compared to passing an actual law with Congressional approval… an EO is “quick” because the President can issue it without getting legislative approval (for things that are in the Presidential remit), but for the same reason an EO also isn’t “durable” or guaranteed to outlive its administration. Because the next President can just order something different, an EO’s default shelf life is just 1-4 years.

So far, all the major U.S. cybersecurity EOs that could affect C++ have been issued since 2021, which means so far they have all come from one President… and so we’re all going to learn a lot this year, one way or another, about their permanence. (In both the U.S. and the E.U., actual laws are also in progress to shift software liability from consumer to software producers, and those will have real teeth. But here we’re talking about the U.S. EOs from 2021 to date.)

That said, what I see in these EOs is common sense pragmatism that’s forcing the software industry to eat our vegetables, so I’m cautiously optimistic that we’ll continue to maintain something like these EOs and build on them further as we continue to work hard to secure the infrastructure that our comfortable free lifestyle (and, possibly someday, our lives) depends on. This isn’t about whether we love a given programming language, it’s about how we can achieve the greatest hardening at the greatest possible scale for our civilization’s infrastructure, and for those of us whose remit includes the C++ language that means doing everything we can to harden as much of the existing C and C++ code out there as possible — all the programmers in the world can only write so much new/rewritten code every year, and for us in C++ by far the maximum contribution we can make to overall security issues related to programming languages (i.e., the subset of security issues that fall into our remit) is to find ways to improve existing C and C++ code with no manual source code changes — that won’t always be possible, but where it’s possible it will maximize our effectiveness in improving security at enormous scale. See also this 2-minute answer I gave in post-talk Q&A in Poland two months ago.

Speaking at University of Waterloo on January 15

Next week, on January 15, I’ll be speaking at the University of Waterloo, my alma mater. There’ll be a tech talk on key developments in C++ and why I think the language’s future over the next decade will be exciting, with lots of time allocated to a “fireside chat / interview” session for Q&A. The session is hosted by Waterloo’s Women in Computer Science (WiCS) group, and dinner and swag by Citadel Securities, where I work.

This talk is open to Waterloo students only (registration required). The organizers are arranging an option to watch remotely for the half of you who are away from campus on your co-op work terms right now — I vividly remember those! Co-op is a great experience.

I look forward to meeting many current students next week, and comparing notes about co-op work terms, pink ties (I still have mine) and MathSoc and C&D food (if Math is your faculty), WATSFIC, and “Water∞loo” jokes (I realize doing this in January is tempting the weather/travel gods, but I do know how to drive in snow…).

My code::dive talk video is available: New Q&A

Two weeks ago, Bjarne and I and lots of ISO committee members had a blast at the code::dive C++ conference held on November 25, just two days after the end of the Wrocław ISO C++ meeting. Thanks again to Nokia for hosting the ISO meeting, and for inviting us all to speak at their conference! My talk was an updated-and-shortened version of my CppCon keynote (which I also gave at Meeting C++; I’ll post a link to that video too once it’s posted):

If you already saw the CppCon talk, you can skip to these “new parts at the end” where the Q&A got into very interesting topics:

Finally, I’m glad I got a chance to give this last answer to cap things off, and thanks again for the audience question that led to it:

That morning, on our route while traveling from the hotel to the conference site, at one point we noticed that up ahead there was a long line of people all down the length of a block and wrapped around the corner. It took me a few beats to realize that was where we were going, and those were the people still waiting to get in to the conference (at that time there were already over 1,000 people inside the building). Here’s one photo that appeared in the local news showing part of the queue:

In all, I’m told 1,800 people attended on-site, and 8,000 attended online. Thank you again to our Nokia hosts for hosting the ISO C++ meeting and inviting us to code::dive, and thank you to all the C++ developers (and, I’m sure, a few C++-curious) who came from Poland and beyond to spend a day together talking about our favorite programming language!

(*) Here’s a transcript of what I said in that closing summary:

… Reflection and safety improvements as what I see are the two big drivers of our next decade of C++.

So I’m excited about C++. I really think that this was a turning point year, because we’ve been talking about safety for a decade, the Core Guidelines are a decade old, we’ve been talking about reflection for 20 years in the C++ committee — but this is the year that it’s starting to get real. This is the year we put erroneous behavior [in] and eliminated uninitialized locals in the standard, this is the year that we design-approved reflection for the standard — both for C++26 and hopefully they’ll both get in. We are starting to finally see these proposals land, and this is going to create a beautiful new decade, open up a new fresh era of C++. Bjarne [….] when C++11 came out, he said, you know, there’s been so many usability improvements here that C++11, even though it’s fully compatible with C++98, it feels like a new language. I think we’re about to do that again, and to make C++26 feel like a new language. And then just as we built on C++11 and finished it with C++14, 17, 20, the same thing with this generation. That’s how I view it. I’m very hopeful for a bright future for C++. Our language and our community continues to grow, and it’s great to see us addressing the problems we most need to address, so we have an answer for safety, we have an answer for simpler build systems and reducing the number of side languages to make C++ work in practice. And I’m looking forward to the ride for the next decade and more.

And at the end of the Q&A, the final part of my answer about why I’m focused on C++ rather than other efforts:

Why am I spending all this time in ISO C++? Not just because I’m some C++-lover on a fanatical level — you may accuse me of that too — but it’s just because I want to have an impact. I’m a user of this world’s society and civilization. I use this world’s banking system. I rely on this world’s hospital system. I rely on this world’s power grid. And darnit I don’t want that compromised, I want to harden it against attack. And if I put all my energy into some new programming language, I will have some impact, but it’s going to be much smaller because I can only write so much new code. If I can find a way to just recompile — that’s why you keep hearing me say that — to just recompile the billions of lines of C++ code that exist today, and make them even 10% safer, and I hope to make them much more than that safer, I will have had an outsized effect on securing our civilization. And I don’t mean to speak too grandiosely, but look at all the C++ code that needs fixing. If you can find a way to do that, it will have an outsized impact and benefit to society. And that’s why I think it’s important, because C++ is important — and not leaving all that code behind, helping that code too as well as new code, I think is super important, and that’s kind of my motivation.

A new chapter, and thoughts on a pivotal year for C++

Starting today I’m excited to be working on a new team, with my C++ standards and community roles unchanged. I also wanted to write a few words about why I’m excited about continuing to invest my time heavily in C++’s standardization and evolution especially now, because I think 2024 has been a pivotal year for C++ — and so this has turned into a bit of an early “year-end C++ retrospective” post too.

It’s been a blast to be on the Microsoft Visual C++ compiler team for over 22 years! The time has flown by because the people and the challenges have always been world-class. An underappreciated benefit of being on a team that owns a foundational technology (like a major C++ compiler) is that you often don’t have to change teams to find interesting projects, because new interesting projects need compiler support and so tend to come to you. That’s been a real privilege, and why I stuck around way longer than any other job I’ve held. Now I am finally going to switch to a new job, but I’ll continue to cheer my colleagues on as a happy MSVC user on my own projects, consuming all the cool things they’re going to do next!

Today I’m thrilled to start at Citadel Securities, a firm that “combines deep trading acumen with leading-edge analytics and technology to deliver liquidity to some of the world’s most important markets, retail brokerages, and financial institutions.” I’ve known folks at CitSec for many years now (including some who participate in WG 21) and have long known it to be a great organization with some of the brightest minds in engineering and beyond. Now I’m looking forward to helping to drive CitSec’s internal C++ training initiatives, advise on technical strategy, share things I’ve learned along the way about sound design for both usability and pragmatic adoptability, and mentor a new set of talented folks there to not only take their own skilled next steps but also to themselves become mentors to others in turn. I think a continuous growth and learning culture like I’ve seen at CitSec consistently for over a dozen years is one of the most important qualities a company can have, because if you have that you can always grow all the other things you need, including as demands evolve over time. But maybe most of all I’m looking forward to learning a lot myself as I dive back into the world of finance — finance is where I started my junior career in the 80s and 90s, and I’m sure I’ll learn a ton in CitSec’s diverse set of 21st-century businesses that encounter interesting, leading-edge technical challenges every day that go well beyond the ones I encountered back in the 20th.

My other C++ community roles are unchanged — I’m continuing my current term as chair of the ISO C++ committee, I’m continuing as chair of the Standard C++ Foundation, and especially I’m continuing to work heavily on ISO C++ evolution (I have eight papers in the current mailing for this month’s Wrocław meeting!) including supporting those with cppfront prototype implementations. I meant it when I said in my CppCon talk that C++’s next decade will be dominated by reflection and safety improvements, and that C++26 really is shaping up to be the most impactful release since C++11 that started a new era of C++; it’s an exciting time for C++ and I plan to keep spending a lot of time contributing to C++26 and beyond.

Drilling down a little: Why is 2024 a pivotal year for C++? Because for the first time in 2024 the ISO committee has started adopting (or is on track to soon adopt) serious safety and reflection improvements into the draft C++ standard, and that’s a big turning point:

  • For safety: With uninitialized local variables no longer being undefined behavior (UB) in C++26 as of March 2024, C++ is taking a first serious step to really removing safety-related UB, and achieve the ‘holy grail’ of an easy adoption story: “Just recompile your existing code with a C++26 compiler, with zero manual code changes, and it’s safer with less UB.” This month, I’m following up on that proposing P3436R1, a strategy for how we could remove all safety-related UB by default from C++ — something that I’m pretty sure a lot of folks can’t imagine C++ could ever do while still remaining true to what makes C++ be C++, but that in fact C++ has already been doing for years in constexpr code! The idea I’m proposing is to remove the same cases of UB we already do in constexpr code also at execution time, in one of two ways for each case: when it’s efficient enough, eliminate that case universally the same as we just did for uninitialized locals; otherwise, leverage the great ideas in the Profiles proposals as a way to opt in/out of that case (see P3436 for details). If the committee likes the idea enough to encourage me to go do more work to flesh it out, over the winter I’ll invest the time to expand the paper into a complete catalog of safety-related UB with a per-case proposal to eliminate that UB at execution time. If we can really achieve a future C++ where you can “just recompile your existing code with safety Profiles enabled, and it’s safer with zero safety-related UB,” that would be a huge step forward. (Of course, some Profiles rules will require code changes to get the full safety benefits; see the details in section 2 of my supporting Profiles paper.)
  • For reflection: Starting with P2996R7 whose language part was design-approved for C++26 in June 2024, we can lay a foundation to then build on with follow-on papers like P3294R2 and P3437R1 to add generation and more features. As I demonstrated with examples in the above-linked CppCon talk, reflection (including generation) will be a game-changer that I believe will dominate the next decade of C++ as we build it out in the standard and learn to use it in the global C++ community. I’m working with P2996/P3294 prototypes and my own cppfront compiler to help gather usability experience, and I’m contributing my papers like P0707R5 and P3437R1 as companion/supporting papers to those core proposals to try to help them progress.

As Bjarne Stroustrup famously said, “C++11 [felt] like a new language,” starting a new “modern” C++ style featuring auto and lambdas and standard safe smart pointers and range-for and move semantics and constexpr compile-time code, that we completed and built on over the next decade with C++14/17/20/23. (And don’t forget that C++11’s move semantics already delivered the ideal adoption story of “just recompile your existing code with a C++11 compiler, with zero manual code changes, and it’s faster.”) Since 2011 until now, “modern C++” has pretty much meant “C++ since C++11” because C++11 made that much of a difference in how C++ worked and felt.

Now I think C++26 is setting the stage to do that again for a second time: Our next major era of what “modern C++” will mean will be characterized by having safety by default and first-class support for reflection-based generative compile-time libraries. Needless to say, this is a group effort that is accomplished only by an amazing set of C++ pros from dozens of countries, including the authors of the above papers but also many hundreds of other experts who help design and review features. To all of those experts: Again, thank you! I’ll keep trying to contribute what I can too, to help ship C++26 with its “version 1” of a set of these major new foundational tools and to continue to add to that foundation further in the coming years as we all learn to use the new features to make our code safer and simpler.

C++ is critically important to our society, and is right now actively flourishing. C++ is essential not only at Citadel Securities itself, but throughout capital markets and the financial industry… and even that is itself just one of the critical sectors of our civilization that heavily depend on C++ code and will for the foreseeable future. I’m thrilled that CitSec’s leadership shares my view of that, and my same goals for continuing to evolve ISO C++ to make it better, especially when it comes to increasing safety and usability to harden our society’s key infrastructure (including our markets) and to make C++ even easier to use and more expressive. I’m excited to see what the coming decade of C++ brings… 2024 really has shaped up to be a pivotal year for C++ evolution, and I can’t wait to see where the ride takes us next.

My AMA yesterday is up on YouTube

Boy, Jens Weller turns these things around quickly! Thanks again, Jens, for having me on your Meeting C++ Live show.

I’ve put a list of the questions, with timestamped links, below…

All the questions and answers, with links

00:19 What are you up to with C++ currently / what keeps you excited?

04:04 Sean Baxter has finally written up a proposal to bring borrow checking to C++, to improve safety. What are your views on his proposal and what approach is Cpp2 planning?

08:48 Is there a long-term vision for C++? How can C++ maintain its relevance in the next 20 years?

13:14 What is your favorite C++ editor/IDE when not using Microsoft Visual Studio?

14:19 Will networking be in C++26?

17:43 Why is MSVC 2022 falling behind Clang and GCC on C++23 and C++26 features?

21:21 What is the roadmap for Cpp2? Whether it will be fit for production use?

26:30 Should the stdlib be split in two parts. One with slow changes and one with fast changes. E.g., ranges were introduced in C++20 but finished in C++23. I am still missing some features.

29:34 Are there plans to address ABIs with interfaces or other features in C++?

36:18 What is your answer to the growing complexity of C++ to be learned especially by novices? How would we teach C++ (e.g., at the university) if it gets larger and larger?

40:53 In the context of C++’s zero-cost abstractions philosophy, how do you see future proposals for making bounds checking in std::vector both safer and more efficient?

47:13 Are C++ safety initiatives arriving too late to fend off the growing adoption of Rust for “safe” low-level development?

55:25 What is the status of the profiles proposal in C++? Will some of it be part of C++26 or C++29?

57:35 The Common Package Specification, which looked very promising, seems stalled. Why is tooling in the language not a priority?

59:11 What do you think of std::execution / P2300R10? The API changed a lot across papers, and to me is quite a piece of work for library implementers to integrate.

1:04:35 Aren’t you afraid that reflection might be misused too much (e.g., use it for serialization)?

1:06:46 If local uninitialized variables are no longer UB, how will they behave? Could you please elaborate a bit on that?

1:11:30 How is the Contracts TS coming along? What are your thoughts on Contract Based Programming, in general?

1:15:56 Any chance of having type erasure (mainly std::any) in MSVC reimplemented not on top of RTTI? Unfortunately the current implementation makes it unusable in places where symbol names are left behind by RTTI.

1:17:38 What happened with the official publication of the C++23 standard?

1:22:31 Preview of my keynote next month at Meeting C++.