Replace CRTP with Concepts -- Sandor Dargo

By Blog Staff | Jan 15, 2025 11:15 AM | Tags: None

This article explores how C++20 concepts can replace CRTP when implementing static interfaces for a family of classes. By leveraging concepts, we achieve cleaner, more readable, and less error-prone code—provided you have access to C++20.

Replace CRTP with Concepts

by Sandor Dargo

From the article:

In my Meeting C++ 2024 trip report, among my favourite ideas I mentioned Klaus Iglberger’s talk where he mentioned the possibility of replacing the curiously returning template pattern with the help of class tagging and concepts.

Class tagging might mean different things in different contexts, or at least might be implemented in different ways. The end goal is to mark, in other words, tag classes or functions to be used in certain contexts, with certain algorithms. As you’ll see, in our case it’ll also be a tool to prevent duck typing.

We are going to see an example implementation of a static interface with CRTP with a couple of different derived classes, then we’ll see the implementation without CRTP.

The CRTP solution

With the static interface, we are creating a static family of types. There is no need for dynamic polymorphism to share the same interface. It’s still granted through a base class, which is a template taking the deriving class as a parameter.

 

 

Solving the Puzzle of Trying to Put an Object into a std::optional -- Raymond Chen

By Blog Staff | Jan 10, 2025 11:06 AM | Tags: None

Last time, we investigated the puzzle of why the compiler wouldn’t let us put an object into a std::optional. It came down to the fact that the object is not copy-constructible, move-constructible, copy-assignable, or move-assignable, so there’s no way to put the temporary object into the std::optional.

Solving the Puzzle of Trying to Put an Object into a std::optional

by Raymond Chen

From the article:

What we have to do is construct the object in place inside the std::optional. And the C++ standard library term for “construct an object inside a container” is “emplace”.

struct Doodad
{
    Doodad();
    ~Doodad();
    std::unique_ptr<DoodadStuff> m_stuff;
};

struct Widget
{
    std::optional<Doodad> m_doodad;

    Widget()
    {
        if (doodads_enabled()) {
            m_doodad.emplace();
        }
    }
};

The parameters to emplace are whatever parameters you would have passed to the Doodad constructor. In our case, we wanted the default constructor, so that means that we pass nothing to emplace().

Court is in session: Top 10 most notorious C and C++ errors in 2024

By Andrey Karpov | Jan 8, 2025 07:28 AM | Tags: top 10 pvs-studio errors bugs

Every year, we witness the same drama: bugs wreak havoc on our code as if asserting their dominance. But today, the tide turns—it's time for judgment. Let's dive into the most intriguing bugs we've uncovered this year.

Court is in session: Top 10 most notorious C and C++ errors in 2024

by Aleksandra Uvarova

From the article:

The seventh defendant, what are you draggin' behind your back? Show us quickly! Ah! A little thief! Decided to pocket a juicy chunk of code, huh? No chance, we're bringing this to the light. Honestly, we really wanted to paste the full code of the function here—which has almost 400 code lines—to make searching for errors more interesting. However, we don't want to abuse your mouse wheel, so we've included just the most intriguing part.

Write More C++ Code Thanks to constexpr -- Andreas Fertig

By Blog Staff | Jan 6, 2025 11:15 AM | Tags: None

Since its introduction, constexpr in C++ has evolved significantly, offering powerful ways to optimize code at compile-time. This article shares a real-world story of using constexpr to dramatically reduce memory usage and code size in an embedded system, showcasing its potential to improve both performance and efficiency.

Write More C++ Code Thanks to constexpr

by Andreas Fertig

From the article:

I'm a big fan of constexpr and am not alone. Jason Turner is also very vocal, having coined the term "constexpr all the things".

Well, demonstrating the powers of constexpr is nonetheless something difficult. I know that from my training classes and various consulting contracts. Today, I'd like to share a story from back in time when a customer hired me to consult. They did develop an embedded system and ran out of memory. Not during run-time, but before. The features they wanted to put in the chip were too big in code size and somewhat RAM.

Initial constexpr-free example

They used a class I've seen a couple of times in embedded systems with some variations. A string brings its memory picky-back.

It’s just ‘,’ – The Comma Operator -- Coral Kashri

By Blog Staff | Jan 3, 2025 11:07 AM | Tags: None

We all know that every ‘,’ matters in this language, so I decided to talk directly about that character today. So, how much impact can be for such a small little character?

It’s just ‘,’ – The Comma Operator

by Coral Kashri

From the article:

This operator comes from C, where it tells the compiler to evaluate all the expressions (left to right) and to return the result of the latest evaluated expression. For example:

     int a, b;

     a = 5, b = 4, b += a, ++a, std::cout << b << " " << a; // Prints 9 6

Another example of that operator usage is as follows:

     for (size_t i = 0, k = 500; i < 10; ++i, ++k) { /*...*/ }

We can see this operator in action in the third section of the for statement. It evaluates the ++i and then evaluates ++k.