Code Generation in Rust vs C++26 -- Barry Revzin

By Blog Staff | Oct 22, 2024 10:30 AM | Tags: None

Exploring how different languages solve the same problem often reveals interesting contrasts, especially when it comes to implementing powerful features like reflection. While C++26 aims to introduce introspection and code generation via P2996 and P3294, Rust’s approach using its derive macros offers a mature solution for code generation, even without introspection, highlighting different philosophies in language design and their practical applications.

Code Generation in Rust vs C++26

by Barry Revzin

From the article:

One of the things I like to do is compare how different languages solve the same problem — especially when they end up having very different approaches. It’s always educational. In this case, a bunch of us have been working hard on trying to get reflection — a really transformative language feature — into C++26. Fundamentally, reflection itself can be divided into two pieces:

1. Introspection — the ability to ask questions about your program during compilation
2. Code Generation — the ability to have your code write new code

P2996 (Reflection for C++26) is the (huge) core proposal that fundamentally deals with the first problem, along with setting the foundation for being able to extend this feature in lots of different directions in the future, including generation (for which our design is P3294). But introspection, while valuable, is only half of the piece. Andrei Alexandrescu went so far as to claim in his CppCon talk that introspection without generation is useless.

2024-10 Mailing Available

By Administrator | Oct 17, 2024 09:36 PM | Tags: None

The 2024-10 mailing of new standards papers is now available.

Synchronization Primitives in C++20 -- Shivam Kunwar

By Blog Staff | Oct 17, 2024 10:20 AM | Tags: None

In C++20, the standard library introduced new synchronization primitives: std::latch and std::barrier. These are the utilities designed to coordinate between concurrent threads.

Synchronization Primitives in C++20

by Shivam Kunwar

From the article:

What is a synchronization primitive?

In concurrent programming, synchronization primitives are the fundamental tools that help in managing the coordination, execution order, and data safety of multiple threads or processes that run concurrently.

Briefly said, they ensure that:

• multiple threads don’t simultaneously execute some specific segment of code (a “critical section”)
• the program and the data remain in a consistent state
• deadlocks (where threads wait indefinitely for resources) and race conditions (where the outcome depends on the timing of accessing the shared data by a thread) are prevented or managed

There are multiple synchronization primitives in C++; for example, mutual exclusion, condition variables, atomic operations, locking mechanisms, etc.

In C++20, we have two additional synchronization primitives: latches and barriers.

Let’s discuss both of them.

std::latch

A std::latch is a synchronization primitive that permits a certain number of count_down operations (decrements) before allowing one or more threads to pass the wait point. A latch cannot be reused once its internal counter reaches zero.

How do we use a latch?

• A std::latch object is created with an initial count.
• Multiple threads can decrement this count using the count_down method.
• Threads can call wait, which block until the internal count of the latch reaches zero.

 

30 days until Meeting C++ 2024!

By Meeting C++ | Oct 15, 2024 06:56 AM | Tags: meetingcpp conference community

Meeting C++ 2024 is just 30 days away! Come to Berlin and meet with the C++ Community and the C++ committee for 3 days!

The Schedule of Meeting C++ 2024

by Jens Weller

From the page:

Meeting C++ 2024 features 4 keynotes, 3 tracks onsite and one online track, the conference is live streamed from Berlin. All Tickets include access to the videos after the conference.

This years keynotes are Titus Winters, Hana Dusíková, Herb Sutter and Peter Sommerlad!

Write Modern Code with Features of C++17 and C++20 -- Andreas Fertig

By Blog Staff | Oct 14, 2024 10:13 AM | Tags: None

When you transition from older C++ standards like C++11 or C++14 to the latest C++17 and C++20 it can be a tough journey. It's essential for writing clean and easy-to-maintain code, but many developers find the process challenging.

Write Modern Code with Features of C++17 and C++20

by Andreas Fertig

From the article:

Here are three common hurdles:

1. Variety of New Features

Adapting to C++17 and C++20 can be intimidating. As the latest standards offer a wide range of new features and syntax changes. One such feature is the introduction of structured bindings in C++17, which represents a shift from how variables were traditionally declared and accessed.

Old Way (C++14 and Earlier):

Before C++17, when you needed to unpack values from a pair or a tuple, you would typically do something like this:

Here, you need to use std::get<>() to access each element of the tuple, which is both verbose and less intuitive, especially when dealing with more complex data structures.

C++ Compile-Time Programming -- Yongwei Wu

By Wu Yongwei | Oct 13, 2024 08:04 AM | Tags: None

<img alt="ACCU" data-cke-saved-src="https://isocpp.org/files/img/logo.png" src="https://isocpp.org/files/img/logo.png" 225px;="" height:="" 60px;="" float:="" right;"="" style="float: right;">Programming at compile time has been possible in C++ for a long time. Yongwei Wu considers its past, present, and future.

C++ Compile-Time Programming

by Yongwei Wu

From the article:

Compile-time programming is a key feature of C++. It enables writing high-performance code often unattainable in other languages. This article explores its past, present, and future applications, highlighting the diverse possibilities in C++. We’ll briefly cover template metaprogramming, constexpr, variadic templates, static reflection, and more.

How To Convert Unicode Strings to Lower Case and Upper Case in C++ -- Giovanni Dicanio

By Giovanni Dicanio | Oct 13, 2024 08:02 AM | Tags: None

Converting Unicode strings to lower and upper cases should be an easy task to accomplish. Unfortunately, that is not the case with C++. Even the so common approach of iterating "char-by-char" in the input string and invoking std::tolower/toupper is wrong. Let's discuss a possible solution to this problem in this article:

How To Convert Unicode Strings to Lower and Upper Case in C++

by Giovanni Dicanio

From the article:

[...] A possible solution to properly convert Unicode strings to lower and upper cases in Windows C++ code is to use the LCMapStringEx Windows API. This is a low-level C interface API.

I wrapped it in higher-level convenient reusable C++ code, available here on GitHub. I organized that code as a header-only library: you can simply include the library header, and invoke the ToStringLower and ToStringUpper helper functions.

 

AMA with Herb Sutter - Meeting C++ live

By Meeting C++ | Oct 12, 2024 05:56 AM | Tags: meetingcpp community c++26 c++23 c++20 basics advanced

Meeting C++ hosted an online AMA with Herb Sutter on Friday.

AMA with Herb Sutter - Meeting C++ live

by Jens Weller & Herb Sutter

Video:

What is std::ref? -- Sandor Dargo

By Blog Staff | Oct 11, 2024 10:06 AM | Tags: None

When working with C++ standard containers and functions, handling references can sometimes lead to unexpected behavior, particularly with copy semantics. This is where std::ref and std::cref come into play, allowing you to store references in containers and pass them safely to template functions like std::bind or std::thread.

What is std::ref?

by Sandor Dargo

From the article:

Have you heard about std::ref and std::cref? The helper functions that generate objects of type std::reference_wrapper? The answer is probably yes. In that case, this article is probably not for you. But if you haven’t heard about them, or the only usage of std::reference_wrapper you faced was storing references in a vector, then probably it’s worth reading on.

This article is inspired by some failing tests that needed me to use std::ref in order to pass them.

What does reference_wrapper do?

A reference of an object T (T&) is not copy assignable. On the other hand, std::reference_wrapper<T> which emulates T& it both copy-constructible and copy-assignable. It’s even trivially copyable, so copying can take place on a byte level which makes it very efficient.

So when should we use such a wrapper?

Learn Modern C++ at Meeting C++ 2024!

By Meeting C++ | Oct 9, 2024 10:59 AM | Tags: meetingcpp learning event community c++26 c++23 c++20

A post highlighting some of the talks that let you learn about Modern C++ at Meeting C++ 2024

Learn Modern C++ at Meeting C++ 2024

by Jens Weller

From the article:

I think this is what should you get excited the most, C++20 is making its way through the compiler implementations and you actually can apply this to your own code base. The top voted talk this year reflects this, in C++ Modules - getting started today Andreas Weis will show you how Modules are now available with the big 3 compilers.

...

Trainings at Meeting C++

After Meeting C++ 2024 there is a trainings week in the last week of November, you an choose between trainings from Kevlin Henney, Slobodan Dimtrovic and Nicolai Josuttis:

    Programming with Guts by Kevlin Henney
    C++ for C Developers - Migrating from C to C++ by Slobodan Dimtrovic
    Generic programming in C++ with templates and auto by Nico Josuttis
    Concepts, Ranges, and Views - The New Way of Programming in C++ by Nico Josuttis