Once More About dynamic_cast, a Real Use Case -- Sandor Dargo

By Blog Staff | Aug 21, 2025 08:13 AM | Tags: None

While dynamic_cast is often discouraged for its impact on readability and reliance on RTTI, there are rare situations where it can be the most practical and safe solution. In this post, we explore one such real-world case: using dynamic_cast for runtime versioning of plugin interfaces in a way that balances compatibility, safety, and extensibility.

Once More About dynamic_cast, a Real Use Case

by Sandor Dargo

From the article:

I wrote a couple of times about dynamic_cast and I discouraged you from using it. In general, it makes code worse in terms of readability. When you get rid of dynamic_cast, either via self-discipline or by turning RTTI off, you’ll have to rely on dynamic dispatching and better abstractions.

But there might be cases, when it’s not possible or at least it’s not meaningful to remove dynamic_cast, here is one, sent by one of you.

Versioning with the help of dynamic_cast

They have an SDK that anyone can implement. As there are new features added every now and then, the API keeps changing. Not surprisingly, the owners of the SDK want to prevent their users’ code from breaking. They achieve this by having different “versioned” interfaces for the same service where a new version inherits from the previous one.

Let’s see a simplified example.

CppCon 2025 Best Practices for AI Tool Use -- Jason Turner

By Blog Staff | Aug 20, 2025 08:40 AM | 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!

Best Practices for AI Tool Use

Wednesday, September 17 09:00 - 10:00 MDT

by Jason Turner

Summary of the talk:

AI (LLMs) are becoming prolific in C++ tooling. Virtually everything has an AI bot built in or available to it. Common wisdom says that these tools simply regurgitate what they find on the internet. As we all know, the internet is full of terrible examples of outdated memory leaks, undefined behavior, and worse!

How do we effectively and safely use these tools while ensuring good code quality?!

Jason is host of the YouTube channel C++Weekly, co-host emeritus of the podcast CppCast, author of C++ Best Practices, and author of the first casual puzzle books designed to teach C++ fundamentals while having fun!

Trip report: C++ On Sea 2025 -- Sandor Dargo

By Blog Staff | Aug 19, 2025 07:10 AM | Tags: None

Another year, another trip report from C++ On Sea!

Trip report: C++ On Sea 2025

by Sandor Dargo

From the article:

First, a heartfelt thank-you to the organizers for inviting me to speak, and an equally big thank-you to my wife for taking care of the kids while I spent three days in Folkestone — plus a few more in London to visit the Spotify office and catch up with some bandmates.

If you have the chance, try to arrive early or stay around Folkestone for an extra day. It’s a lovely town and it’s worth exploring it. The conference program is very busy even in the evenings, so don’t count on the after hours.

This year, I arrived an half a day in advance and I had a wonderful hike from Folkestone to Dover. It was totally worth it.

In this post I’ll share:

• Thoughts on the conference experience.
• Highlights from talks and ideas that resonated with me.
• Personal impressions, including reflections on my own sessions — both the main talk and the lightning talk.

CppCon 2025 std::optional --- Optional Over References -- Steve Downey

By Blog Staff | Aug 18, 2025 02:36 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!

std::optional --- Optional Over References

Tuesday, September 16 15:15 - 16:15 MDT

by Steve Downey

Summary of the talk:

Optionals were first proposed for C++ in 2005.

Optional , where T is constrained not to be a reference, was added in 2017.

Optionals for lvalue references are on track to be added in C++ 26.

What are we getting and what design choices were made? This talk will show the results.

This talk will discuss the early history of Optionals, starting with Boost.Optional and “N1878: A Proposal to Add an Utility Class to Represent Optional Objects (Revision 1)”, and what the early concerns were for the reference specialization. “P1175R0: A Simple and Practical Optional Reference for C++” then re-proposed reference support for C++20, which was not adopted. In 2020, “P1683R0: References for Standard Library Vocabulary Types - an optional<> case study” surveyed existing behavior of optional references in the wild, and pointed out the trap of assignment behavior being state dependent. In 2023, “P2988R0: Std:Optional” picked up the torch again, and Revision 10 of that is the proposal that is approved by the Library Working Group.

In 2024, “P3168R0: Give Std:Optional Range Support”, the proposal to make optional a range -- as opposed to having a separate range of zero or one -- was adopted. The reference implementation for optional

Steve Downey has been a programmer for more than 30 years. Steve graduated from SUNY Purchase with a BS in Mathematics. A Computer Science degree would have involved two classes before 11:00 am, so was impossible.

He has worked at Bloomberg since 2003, and is currently working as an Engineer on the C++ Infrastructure team.

CppCon 2025 Back to Basics: Refactoring -- Amir Kirsh

By Blog Staff | Aug 16, 2025 02:36 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: Refactoring

Tuesday, September 16 09:00 - 10:00 MDT

by Amir Kirsh

Summary of the talk:

Writing C++ code is one thing, keeping it clean, readable and maintainable over time is another. In this talk, we'll review the basics of refactoring C++ code, focusing on strategies to improve code clarity, reduce duplication, and make your code easier to maintain. You'll learn how to identify code smells, recognize when refactoring is needed, and apply techniques to improve readability. We will also explore how to modernize your code by leveraging new C++ features when relevant, ensuring that your code not only adheres to best practices but is also aligned with the evolving standards of the language. Participants will gain practical knowledge on how to refactor C++ code to enhance clarity, reduce complexity, and improve long-term maintainability, a skill that becomes even more essential as AI starts generating parts of our codebase. This talk is part of the Back to Basics track and is designed for C++ beginners, but it can also be useful for intermediate and experienced developers who want to revisit the fundamentals of maintaining clean, well-structured C++ code through effective refactoring.

Amir Kirsh is a C++ lecturer at the Academic College of Tel-Aviv-Yaffo and Tel-Aviv University, previously the Chief Programmer at Comverse, after being CTO and VP R&D at a startup acquired by Comverse. He is also a co-organizer of the annual Core C++ conference and a member of the ISO C++ Israeli National Body.

2025-08 Mailing Available

By Administrator | Aug 15, 2025 05:33 PM | Tags: None

The 2025-08 mailing of new standards papers is now available.

A virtual destructor in C++, when? -- Andreas Fertig

By Blog Staff | Aug 15, 2025 08:04 AM | Tags: None

When should a destructor be virtual in C++? In this post, we’ll explore a real-world example from smart pointer implementation to illustrate when virtual destructors are necessary — and when they’re not.

A virtual destructor in C++, when?

by Andreas Fertig

From the article:

In today's post, I would like to explain a design rationale used in my post Understanding the inner workings of C++ smart pointers - The shared_ptr.

Keen readers spotted that in my implementation of ctrl_blk_base, I didn't make the destructor virtual. Here is the original code for easy reference:

PVS-Studio 7.38: new C++ analyzer core

By Andrey Karpov | Aug 15, 2025 01:42 AM | Tags: sast pvs-studio parser misra

PVS-Studio 7.38 has been released. This version brings the new core for the C and C++ analyzer, the user annotation mechanism in the Java analyzer, enhanced taint analysis, and that's not all! See more details in this note.

PVS-Studio 7.38: new C++ analyzer core, user annotations in Java, enhanced taint analysis, and more

by Aleksandra Uvarova

From the article:

The C and C++ analyzer got a new core with completely redesigned components like a parser, a semantic analyzer, and a type system. The new core provides more accurate handling of template constructs and better parsing of the standard library and code based on modern C++ standards. During the extended testing period (EAP), the new core demonstrated stable performance across a wide range of real-world projects.

CppCon 2025 Missing Step: Making Data Oriented Design One Million Times Faster -- Andrew Drakeford

By Blog Staff | Aug 14, 2025 09:31 AM | 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!

The Missing Step: Making Data Oriented Design One Million Times Faster

Tuesday, September 16 09:00 - 10:00 MDT

by Andrew Drakeford

Summary of the talk:

Data-oriented design (DOD) has gained traction for its practical approach to solving real-world problems. Refactoring data into an Entity-Component format sets the stage for cleaner, more efficient implementations, where lambdas process ranges and SIMD operations exploit the power of contiguous data layouts. DOD is widely recognised for addressing hardware-related performance challenges, but where do these challenges originate? The engineers behind our hardware platforms didn’t design performance bottlenecks; they created performance opportunities. By engineering how our code interacts with hardware, we can unlock these opportunities and achieve substantial speed-ups. The key lies in understanding and exploiting the state of the system. From the instruction cache and registers to the L1 cache and memory access patterns, the processor's statefulness plays a crucial role in performance. Writing "hardware-friendly" code is fundamentally about aligning with this state. But hardware is only part of the equation. What about the statefulness of our software? By carefully engineering the sequence of operations and algorithms to align with both hardware and software states, we can achieve unparalleled optimization. This is the missing step. Engaging with the design problem in full can be very difficult. We leverage George Polya’s problem-solving process and heuristics to guide our approach. This presentation explores these principles through real-world examples in machine learning and mathematical finance, demonstrating how addressing both sides of the problem can improve performance by orders of magnitude. (Yes, even six orders of magnitude.) Attendees will leave with insights into the exploration process and actionable techniques that might lead to achieving similar gains in their own work. It has been noted that some attendees might start drawing more diagrams when problem-solving and have an overwhelming urge to get Polya’s book.

Andrew Drakeford A Physics PhD who started developing C++ applications in the early 90s at British Telecom labs. For the last two decades, he has worked in finance developing efficient calculation libraries and trading systems in C++. His current focus is on making quant libraries more ecologically sound. He is a member of the BSI C++ panel.

Reflecting JSON into C++ Objects -- Barry Revzin

By Blog Staff | Aug 13, 2025 08:59 AM | Tags: None

C++26 marks a transformative milestone with the adoption of full compile-time reflection, enabling powerful new metaprogramming capabilities. In this post, we’ll explore how reflection lets you turn a JSON file directly into a fully-typed C++ object — all at compile time.

Reflecting JSON into C++ Objects

by Barry Revzin

From the article:

Last week, C++26 was finalized in Sofia, Bulgaria — and C++26 will include all of the reflection papers that we were pushing for:

1. P2996R13: Reflection for C++26
2. P3394R4: Annotations for Reflection
3. P3293R3: Splicing a Base Class Subobject
4. P3491R3: define_static_{string,object,array}
5. P1306R5: Expansion Statements
6. P3096R12: Function Parameter Reflection in Reflection for C++26
7. P3560R2: Error Handling in Reflection

Those are in the order in which they were adopted, not in the order of their impact (otherwise splicing base classes would go last). This is a pretty incredible achievement that couldn’t have happened without lots of people’s work, but no one person is more responsible for Reflection in C++26 than Dan Katz.

So today I wanted to talk about a very cool example that Dan put together on the flight home from Sofia, while I was unconscious a few seats over: the ability to, at compile time, ingest a JSON file and turn it into a C++ object. That is, given a file test.json that looks like this:

{ "outer": "text", 
"inner": { "field": "yes", "number": 2996 } 
} 

We can write this:

constexpr const char data[] = { 
     #embed "test.json" 
     , 0 

}; constexpr auto v = json_to_object<data>;