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Speaking about C++ is tomorrow

By Meeting C++ | Jun 5, 2024 01:41 AM | Tags: meetingcpp intermediate community basics

Like in the last two years Meeting C++ is organizing an event about technical speaking at C++ conferences, aiming to help new speakers with their talks and give everyone a chance to pick up something to improve their talks! The call for talks for Meeting C++ 2024 is running until June 25th!

Speaking about C++

Organized by Jens Weller

From the event description:

This event will focus on the process of creating technical talks for the C++ community. Various speakers will share their views on how to submit, prepare and give talks to the C++ community in the form of lightning talks and a panel.

Qt and Trivial Relocation (Part 1) -- Giuseppe D'Angelo

By Blog Staff | Jun 4, 2024 03:33 PM | Tags: None

In Qt 4, container classes like QVector introduced an optimization that transformed certain operations on contained objects into efficient byte-level manipulations. By identifying types that can be safely moved via a simple memory copy, Qt was able to streamline reallocations for specific data types like int and QString. This article explores the concept of trivial relocation, how Qt leverages it for optimized data manipulation, and the implications for different container structures and data types.

Qt and Trivial Relocation (Part 1)

by Giuseppe D'Angelo

From the article:

The container classes introduced in Qt 4 (Tulip, for the aficionados) had an interesting optimization: the ability to turn certain operations on the contained objects into byte-level manipulations.

Example: vector reallocation

Consider the reallocation of a QVector<T>: when the vector is full and we want to insert a new value (of type T), the vector has to allocate a bigger block of memory.

Error on verge of extinction, or why I put if (x = 42) in Red List of C & C++ bugs

By Andrey Karpov | Jun 4, 2024 11:14 AM | Tags: yoda notation collection of bugs bugs assignment

If we ask a programmer what bugs are the most common in C and C++ code, they'll name a null pointer dereference, undefined behavior, array overrun, and other typical error patterns. They may name an accidental assignment in condition as well. However, let's see if this error is common today.

Error on verge of extinction, or why I put if (x = 42) in Red List of C & C++ bugs

by Andrey Karpov

From the article:

Because of this bug, developers invented the Yoda notation: a programming style where the constant is placed on the left side of the comparison operator. This style was meant to prevent a typo. If a programmer writes = instead of ==, the code won't compile.

CppCon 2023 Cooperative C++ Evolution - Toward a Typescript for C++ -- Herb Sutter

By Blog Staff | Jun 3, 2024 02:03 PM | Tags: None

Registration is now open for CppCon 2024! The conference starts on September 15 and will be held in person in Aurora, CO. To whet your appetite for this year’s conference, we’re posting videos of some of the top-rated talks from last year's conference. Here’s another CppCon talk video we hope you will enjoy – and why not register today for CppCon 2024!

Plenary: Cooperative C++ Evolution - Toward a Typescript for C++

by Herb Sutter

Summary of the talk:

C++23 is done. But C++ is not! In this talk I’ll give my personal perspectives on:

C++’s ongoing and very active evolution;

The latest progress updates on my cppfront experimental compiler, and what I’ve learned about modern ISO C++20 and C++23 in the experiment (https://github.com/hsutter/cppfront);

Why compatibility (and what kind, and how much) is essential; and

Why we should aim to keep bringing C++ forward successfully by cooperating and being part of C++’s ongoing true evolution via WG 21, even though that’s more work than pursuing a new fresh-but-competing evolutionary path.

CppCon 2023 ClangFormat Is Not It -- Anastasia Kazakova

By Blog Staff | Jun 1, 2024 02:00 PM | Tags: None

Lightning Talk: ClangFormat Is Not It

by Anastasia Kazakova

Summary of the talk:

Sometimes things are not what we think of them. But we keep using them based on our perception. ClangFormat is a widely used tool by the C++ community. Join me to explore the typical delusions around it.

Adding State to the Update Notification Pattern, Part 6 -- Raymond Chen

By Blog Staff | May 30, 2024 03:31 PM | Tags: None

Last time, we built a stateful but coalescing update notification using a change counter to identify which request is the latest one, but noted that it does unnecessary work. Let’s see if we can avoid the unnecessary work.

Adding State to the Update Notification Pattern, Part 6

by Raymond Chen

From the article:

We could add some early exits to abandon the work if we notice that we are no longer doing work on behalf of the most recent text change. It means that we have to switch the change counter variable to a std::atomic since we will be reading the variable from the background thread at the same time the UI thread may be modifying it.
class EditControl
{
    ⟦ ... existing class members ... ⟧

    std::atomic<unsigned> m_latestId;
};

winrt::fire_and_forget
EditControl::TextChanged(std::string text)
{
    auto lifetime = get_strong();

    auto id = m_latestId.fetch_add(1, std::memory_order_relaxed);

    co_await winrt::resume_background();

    if (!IsLatestId(id))) co_return;

    std::vector<std::string> matches;
    for (auto&& candidate : FindCandidates(text)) {
        if (candidate.Verify()) {
            matches.push_back(candidate.Text());
        }
        if (!IsLatestId(id))) co_return;
    }

    co_await winrt::resume_foreground(Dispatcher());

    if (!IsLatestId(id))) co_return;

    SetAutocomplete(matches);
}

bool EditControl::IsLatestId(unsigned id) 
{ 
 return id == m_latestId.load(std::memory_order_relaxed);
} 
The background worker periodically checks whether its work has been discarded and abandons its efforts if so.

HPX V1.10.0 released -- STE||AR Group

By Hartmut Kaiser | May 29, 2024 07:43 AM | Tags: performance parallelism heterogeneous computing distributed computing concurrency c++23 c++20 c++17 c++14 c++11

The STE||AR Group has released V1.10.0 of HPX -- A C++ Standard library for Concurrency and Parallelism.

HPX V1.10.0 Released

We have released HPX 1.10.0 — a major update to our C++ Standard Library for Concurrency and Parallelism. We have continued to modernize HPX to fully conform to the latest standardization efforts in the are of parallelism and concurrency. Our HPX documentation has seen a major overhaul for this release, please have a look here. We finished documenting the public local HPX API, we have added migration guides from widely used parallelization platforms to HPX (OpenMP, TBB, and MPI). Among other things, we have performed a lot of code cleanup and refactoring to improve the overall code quality and decrease compile times and to improve the consistency of our exposed APIs. The core implementation has seen many performance optimizations that impact every aspect of our applications.

If you have any questions, comments, or exploits to report you can reach us on IRC or Matrix (#ste||ar on libera.chat) or email us at hpx-users. We depend on your input!

You can download the release from our releases page or check out the v1.10.0 tag using git. A full list of changes can be found in the release notes.

HPX is a general-purpose parallel C++ runtime system for applications of any scale. It implements all of the related facilities as defined by the C++20 Standard. As of this writing, HPX provides the only widely available open-source implementation of the new C++17, C++20, and C++23 parallel algorithms, including a full set of parallel range-based algorithms. Additionally, HPX implements functionalities proposed as part of the ongoing C++ standardization process, such as large parts of the features related parallelism and concurrency as specified by the upcoming C++23 Standard, the C++ Concurrency TS, Parallelism TS V2, data-parallel algorithms, executors, and many more. It also extends the existing C++ Standard APIs to the distributed case (e.g., compute clusters) and for heterogeneous systems (e.g., GPUs).

HPX seamlessly enables a new Asynchronous C++ Standard Programming Model that tends to improve the parallel efficiency of our applications and helps reducing complexities usually associated with parallelism and concurrency.

Exploring the Impact of Top-Level cv-qualifiers on type-deduction -- Andreas Fertig

By Blog Staff | May 28, 2024 03:30 PM | Tags: None

In today's post, I will continue where I left off with last month's post Understanding the role of cv-qualifiers in function parameters. This time, I will focus on type deduction.

Exploring the Impact of Top-Level cv-qualifiers on type-deduction

by Andreas Fertig

From the article:

CppCon 2023 C++ Modules: Getting Started Today -- Andreas Weis

By Blog Staff | May 27, 2024 01:56 PM | Tags: None

C++ Modules: Getting Started Today

by Andreas Weis

Summary of the talk:

Modules have been one of the most highly anticipated features of C++20. Unfortunately, it was also the language feature that took the longest to become widely available for developers to use. This year, for the first time, we see broad support for the feature in all major compilers and mainstream build system support through CMake. The goal of this talk is to provide you with all the basic knowledge to allow you getting started with C++20 modules today.

We will take a look at how modules change the build process and why it took so long to implement them. We will take a tour of the essentials of the named modules mechanism and explore the new best practices for physical code structure in a modules-based code base, including how to set up a build with CMake. And last but not least, we will discuss different options for interacting with existing header-based code.

The talk will focus above all else on practicality: We will only be covering features that are widely available for use today with the latest compilers and build tools. We will give special attention to the areas where the design practices for modules differ from the familiar header-based approach and address common misconceptions and pitfalls that are typical among developers first encountering the feature. No prior knowledge of modules is required.

CppCon 2023 Higher-Order Template Metaprogramming with C++23 -- Ed Catmur

By Blog Staff | May 26, 2024 01:51 PM | Tags: None

Lightning Talk: Higher-Order Template Metaprogramming with C++23

by Ed Catmur

Summary of the talk:

C++20's Concepts transformed metaprogramming, but they can still be inflexible and are not readily composable. I demonstrate a few simple yet powerful techniques to allow building concepts from type traits, type transformations and even other concepts.