C++ Enum Class and Error Codes -- Mathieu Ropert

By Blog Staff | Dec 5, 2025 03:33 PM | Tags: None

C++11 gave us enum class and while it’s great to have scoped enums I don’t find it great for error handling. Let’s talk about why.

C++ Enum Class and Error Codes

by Mathieu Ropert

From the article:

Most of my readers, I hope, have been able to use C++11 for a while now (if not hello, I’m sorry the world has changed to become this weird during your 14 years sleep). With it came a small change that allowed for better scoping of names without resorting to weird quirks: enum class. The idea is simple: owing to C, enum values in C++ belong to the class or namespace they are declared in but if we add the class keyword to the declaration they know become their own scope instead of leaking to their parent.

This was a simple quality of life change in the compiler to address a weakness in the language that folks usually worked around by either adding long prefix to the enum values (C style) or wrapping them within structs or classes (C++98/03 style). And with it came the incentive to migrate C era error code enums to scoped enums. But there’s a catch.

Trip report: Budapest C++ - Breaking & Building C++ -- Sandor Dargo

By Blog Staff | Dec 3, 2025 03:30 PM | Tags: None

The Budapest C++ Meetup was a great reminder of how strong and curious our local community is. Each talk approached the language from a different angle — Jonathan Müller from the perspective of performance, mine from design and type safety, and Marcell Juhász from security — yet all shared the same core message: understand what C++ gives you and use it wisely.

Trip report: Budapest C++ - Breaking & Building C++

by Sandor Dargo

From the article:

More than a hundred people registered, and the room quickly filled up with local developers eager to hear three technical talks. The atmosphere was lively and welcoming — it showed the strength of the C++ community in Budapest. In 2027, even WG21 might come to Hungary!

The evening began with Jonathan Müller’s talk, Cache-Friendly C++, followed by my own session on Strongly Typed Containers. Finally, Marcell Juhász closed the event with an insightful and hands-on presentation on Hacking and Securing C++.

Speeding up C++ functions with a thread_local cache -- Daniel Lemire

By Blog Staff | Dec 1, 2025 03:25 PM | Tags: None

When working with legacy or rigid codebases, performance bottlenecks can emerge from designs you can’t easily change—like interfaces that force inefficient map access by index. This article explores how a simple thread_local cache can dramatically improve performance in such cases, reducing repeated lookups from quadratic to near-constant time.

Speeding up C++ functions with a thread_local cache

by Daniel Lemire

From the article:

In large code bases, we are often stuck with unpleasant designs that are harming our performance. We might be looking for a non-intrusive method to improve the performance. For example, you may not want to change the function signatures.

Let us consider a concrete example. Maybe someone designed the programming interface so that you have to access the values from a map using an index. 

 

Using RAII to remedy defect where not all code paths performed required exit actions -- Raymond Chen

By Blog Staff | Nov 28, 2025 03:22 PM | Tags: None

A missing DismissUI() call on one code path led to a subtle bug—but rather than patching it with more try/catch and return logic, there’s a cleaner C++ solution. This article shows how to use RAII and wil::scope_exit to guarantee cleanup across all code paths, even in asynchronous callbacks.

Using RAII to remedy a defect where not all code paths performed required exit actions

by Raymond Chen

From the article:

A team asked me to review their pull request that fixed a bug that was caused by failing to perform some required action along all code paths. Here’s a simplified sketch:

void MySpecialFeature::OnButtonClick()
{
    try {
        auto file = PickFile();
        if (!file) {
            DismissUI();
            return;
        }

        if (ConfirmAction()) {
            if (m_useAlgorithm1) {
                // StartAlgorithm1 invokes the lambda when finished.
                StartAlgorithm1(file, [self = shared_from_this()] {
                    self->DismissUI();
                });
            } else {
                RunAlgorithm2(file);
                DismissUI();
            }
        } else { // this block was missing
           DismissUI(); 
        } 
    } catch (...) {
        DismissUI();
    }
}

How to Iterate through std::tuple: C++26 Packs and Expansion Statements -- Bartlomiej Filipek

By Blog Staff | Nov 25, 2025 02:54 PM | Tags: None

In this final part of the tuple-iteration mini-series, we move beyond C++20 and C++23 techniques to explore how C++26 finally brings first-class language support for compile-time iteration. With structured binding packs (P1061) and expansion statements (P1306), what once required clever template tricks can now be written in clean, expressive, modern C++.

C++ Templates: How to Iterate through std::tuple: C++26 Packs and Expansion Statements

by Bartlomiej Filipek

From the article:

In part 1 of this mini-series, we looked at the basics of iterating over a std::tuple using index_sequence and fold expressions. In part 2, we simplified things with std::apply and even created helpers like for_each_tuple and transform_tuple.

So far, we used C++ features up to C++20/23… but now, in C++26, we finally get language-level tools that make tuple iteration straightforward and expressive. In this article, we’ll explore two new techniques:

• Structured bindings can introduce a pack - P1061 - turn a tuple into a pack of variables.
• Expansion statements P1306 - the ultimate “compile-time loop” syntax.

C++ Casts: To lie, and hopefully - to lie usefully - Patrice Roy - Meeting C++ 2025

By Meeting C++ | Nov 23, 2025 09:18 AM | Tags: meetingcpp c++17 c++11 basics advanced

Patrice Roy gave a great talk online on C++ casts at Meetign C++ 2025

To lie, and hopefully - to lie usefully - Patrice Roy - Meeting C++ 2025

by Patrice Roy

Concept-Based Generic Programming -- Bjarne Stroustrup

By Bjarne Stroustrup | Nov 22, 2025 02:14 PM | Tags: None

A new paper:

Bjarne Stroustrup: Concept-Based Generic Programming

https://www.stroustrup.com/Concept-based-GP.pdf

We present programming techniques to illustrate the facilities and principles of C++ generic programming using concepts. Concepts are C++’s way to express constraints on generic code. As an initial example, we provide a simple type system that eliminates narrowing conversions and provides range checking without unnecessary notational or run-time overhead.

User-Defined Formatting in std::format -- Spencer Collyer

By Blog Staff | Nov 21, 2025 02:51 PM | Tags: None

std::format allows us to format values quickly and safely. Spencer Collyer demonstrates how to provide formatting for a simple user-defined class.

User-Defined Formatting in std::format

by Spencer Collyer

From the article:

In a previous article [Collyer21], I gave an introduction to the std::format library, which brings modern text formatting capabilities to C++.

That article concentrated on the output functions in the library and how they could be used to write the fundamental types and the various string types that the standard provides.

Being a modern C++ library, std::format also makes it relatively easy to output user-defined types, and this series of articles will show you how to write the code that does this.

There are three articles in this series. This article describes the basics of setting up the formatting for a simple user-defined class. The second article will describe how this can be extended to classes that hold objects whose type is specified by the user of your class, such as containers. The third article will show you how to create format wrappers, special purpose classes that allow you to apply specific formatting to objects of existing classes.

A note on the code listings: The code listings in this article have lines labelled with comments like // 1. Where these lines are referred to in the text of this article, it will be as ‘line 1’ for instance, rather than ‘the line labelled // 1’.

The Code is Documentation Enough - Tina Ulbrich - Meeting C++ 2025

By Meeting C++ | Nov 20, 2025 07:51 AM | Tags: meetingcpp community

The first video from Meeting C++ 2025. As every year the online track is released first.

The Code is Documentation Enough - Tina Ulbrich - Meeting C++ 2025

by Tina Ulbrich

Watch now:

std::ranges may not deliver the performance that you expect -- Daniel Lemire

By Blog Staff | Nov 19, 2025 02:48 PM | Tags: None

Modern C++ offers elegant abstractions like std::ranges that promise cleaner, more expressive code without sacrificing speed. Yet, as with many abstractions, real-world performance can tell a more nuanced story—one that every engineer should verify through careful benchmarking.

std::ranges may not deliver the performance that you expect

by Daniel Lemire

From the article:

Good engineers seek software code that is ‘simple’ in the sense that we can read and understand it quickly. But they they also look for highly performant code.

For the last 20 years, we have been offering programmers the possibility to replace conventional for loops with a more functional approach. To illustrate, suppose that you want to extract all even integers from a container and create a new container. In conventional C++, you would proceed with a loop, as follows.

std::vector<int> even_numbers;
for (int n : numbers) {
 if (n % 2 == 0) {
 even_numbers.push_back(n);
 }
}