C++23: Deducing This -- Rainer Grimm

By Blog Staff | Aug 14, 2023 01:39 PM | Tags: None

Anyone who thinks a small C++ standard follows a significant C++ standard is wrong. C++23 provides powerful extensions to C++20. These extensions include the core language, particularly the standard library. Today, I present a small but very impactful feature of the core language: deducing this.

C++23: Deducing This

By Rainer Grimm

From the article:

Deducing this, sometimes also called explicit object parameter, allows it to make the implicit this pointer of a member function explicit. Like Python, the explicit object parameter must be the first function parameter and is called in C++, by convention, Self and self.

struct Test {

    void implicitParameter();               // implicit this pointer
    void explictParameter(this Self& self); // explicit this pointer
};

Deducing this enables new programming techniques in C++23: deduplication of function overloading based on the object’s lvalue/rvalue value category and constness. Additionally, you can reference a lambda and invoke it recursively. Furthermore, deducing this simplifies the implementation of CRTP

2023-07 Mailing Available

By Administrator | Aug 14, 2023 07:30 AM | Tags: None

The 2023-07 mailing of new standards papers is now available.

HPX V1.9.1 released -- STE||AR Group

By Hartmut Kaiser | Aug 12, 2023 08:25 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 V1.9.1 of HPX -- A C++ Standard library for Concurrency and Parallelism.

HPX V1.9.1 Released

We have released HPX 1.9.1 that adds a number of small new features and fixes a handful of problems discovered since the last 1.9.0 release. In particular: we fixed various occasional hanging during startup and shutdown in distributed scenarios. We also added support for zero-copy serialization on the receiving side to the TCP, MPI, and LCI parcelports. Moreover, we have added support for Visual Studio 2019 and GCC using MINGW on Windows, and also support for GCC 13 and Clang 15.0.0. Furthermore, we aligned our header names to their standards counterparts so porting from standard C++ to HPX is now easier. Last but not least, and by adhering to popular demand, we started adding migration guides for people interested in moving their codes away from other, commonplace parallelization frameworks like OpenMP and MPI. We have also continued to improve our documentation, please have a look here.

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 v1.9.1 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.

How To Address 7 Major C++ Pain Points with CLion -- Anastasia Kazakiova

By Blog Staff | Aug 10, 2023 01:32 PM | Tags: None

In the 2023 Annual C++ Developer Survey conducted by the C++ Foundation, the community identified a number of major pain points when working with C++.

How To Address 7 Major C++ Pain Points with CLion

By Anastasia Kazakiova

From the article:

As we’ll discuss in this article, CLion can help C++ developers with most of these in various ways:

• Managing third-party libraries
• Improving build times
• Setting up a CI-pipeline
• Managing a CMake project
• Checking code for thread, memory and type safety issues on-the-fly
• Setting up a development environment from scratch
• Modernize your code

RFC - fat pointer class, evolution of YOMM2 -- Reddit Q&A

By Blog Staff | Aug 9, 2023 01:24 PM | Tags: None

Question from reddit poster: I am preparing to release a new feature, a fat pointer class (virtual_ptr), that makes method dispatch even more efficient. Dispatching a method with one virtual argument via a virtual_ptr takes only three instructions and two independent memory reads. As an interesting side-effect, it is now possible to use YOMM2 with non polymorphic classes hierarchies.

RFC - fat pointer class, evolution of YOMM2

From the discussion:

I am preparing to release a new feature, a fat pointer class (virtual_ptr), that makes method dispatch even more efficient. Dispatching a method with one virtual argument via a virtual_ptr takes only three instructions and two independent memory reads. As an interesting side-effect, it is now possible to use YOMM2 with non polymorphic classes hierarchies.

Once I increase the semantic minor version number, I will mostly be stuck with the API. So, if you are interested and in the mood, please review the documentation.

Beyond this, I have been mulling a major version bump. There are a few stuff that are deprecated, and I would like to get rid of them.

Also, I wonder if it would be a good time to switch to C++20. The internals would be a lot simpler and cleaner if I could use concepts.

I have a few major developments on the radar:I have a few major developments on the radar:

• dispatch on std::any and std::variant
• "fat" versions of std::any and std::variant (in the manner of virtual_ptr)
• going headers only
• related to the former: tunable runtime
• quasi static initialization of method tables

I wonder if it would be better to wait until these items are completed before switching to C++20 and putting the C++17 code in bugfix only mode.

Finite State Machine with std::variant - Vending Machine -- Bartlomiej Filipek

By Blog Staff | Aug 7, 2023 01:17 PM | Tags: None

In my last article, we discussed Finite State Machines based on std::variant and some cool C++17 techniques. Today I want to go further and show you an example of a Vending Machine implementation.

Finite State Machine with std::variant - Vending Machine

By Bartlomiej Filipek

From the article:

Here’s a basic diagram that illustrates how the machine is going to work:

Following the model from the last article, each state and the event will be a separate small structure. Later we can “pack” them into std::variant.

C++23: The Next C++ Standard -- Rainer Grimm

By Blog Staff | Aug 5, 2023 01:37 PM | Tags: None

C++23 will be the next C++ standard after C++20. This new standard significantly improves C++ but is less game-changing than C++98, C++11, or C++20. C++23 is more in the tradition of C++17.

C++23: The Next C++ Standard

By Rainer Grimm

From the article:

The C++ Standards

C++ is more than 40 years old. What happened in the last years? Here is a simplified answer ending in C++23.

C++98

At the end of the 80ths, Bjarne Stroustrup and Margaret A. Ellis wrote their famous book Annotated C++ Reference Manual (ARM). These books served two purposes. First, there were many independent C++ implementations. ARM defined, therefore, the functionality of C++. Second, ARM was the base for the first C++ standard: C++98 (ISO/IEC 14882). C++98 had a few essential features: templates, the standard template library (STL) with its containers and algorithms, strings, and IO streams.

C++03

With C++03 (14882:2003), C++98 got a technical correction that is so small that there is no place on my timeline. In the community, C++03, which includes C++98, is called legacy C++.

CppCon 2022 Back to Basics: Debugging in C++ -- Mike Shah

By Blog Staff | Aug 4, 2023 06:12 AM | Tags: None

Registration is now open for CppCon 2023! The conference starts on October 1 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 2023!

Back to Basics: Debugging in C++

by Mike Shah

Summary of the talk:

I always tell my students, the debugger is your 'get out of jail free card' when working on a project. I say the same thing to professionals, debuggers are your 'get out of free jail card'. The reality is that programmers spend the majority of their time debugging as opposed to writing new code. Unfortunately many programmers do not learn how to use a debugger, or otherwise how they should approach debugging. In this talk I am going to show you how to debug C++ code, starting from the very basics and then demonstrating how a debugger like GDB can be used to help you track errors in CPU code. Attendees at this talk will learn names of debugging techniques (e.g. delta debugging), and I will demonstrate several debugging tools (stepping through code, capturing backtraces, conditional breakpoints, scripting, and even time traveling!) to demonstrate the power of debuggers. This is a beginner friendly talk where we are going to start from the beginning, but I suspect I may show a trick or two that folks with prior experience will appreciate.

Constrain your user-defined conversions -- Jonathan Mueller

By Blog Staff | Aug 3, 2023 01:08 PM | Tags: None

Sometimes you want to add an implicit conversion to a type. This can be done by adding an implicit conversion operator. For example, std::string is implicitly convertible to std::string_view.

Constrain Your User-Defined Conversions

By Jonathan Mueller

From the article:

Sometimes you want to add an implicit conversion to a type. This can be done by adding an implicit conversion operator. For example, std::string is implicitly convertible to std::string_view:

	class string { // template omitted for simplicity
	public:
	    operator std::string_view() const noexcept
	    {
	       return std::string_view(c_str(), size());
	    }
	}; 

The conversion is safe, cheap, and std::string and std::string_view represent the same platonic value — we match Tony van Eerd’s criteria for implicit conversions and using implicit conversions is justified.

However, even when all criteria are fulfilled, the conversion can still be dangerous.

Thread-Safe Queue - Two Serious Errors -- Rainer Grimm

By Blog Staff | Aug 1, 2023 03:12 PM | Tags: None

In my last post "Monitor Object"  I implemented a thread-safe queue. I made two serious errors. Sorry. Today, I will fix these issues.

Thread-Safe Queue - Two Serious Errors

by Rainer Grimm

From the article:

First, I want to show you again the erroneous implementation from my last post to understand the context.

// monitorObject.cpp

#include <condition_variable>
#include <functional>
#include <queue>
#include <iostream>
#include <mutex>
#include <random>
#include <thread>

class Monitor {
public:
    void lock() const {
        monitMutex.lock();
    }

    void unlock() const {
        monitMutex.unlock();
    }

    void notify_one() const noexcept {
        monitCond.notify_one();
    }

    template <typename Predicate>
    void wait(Predicate pred) const {                 // (10)
        std::unique_lock<std::mutex> monitLock(monitMutex);
        monitCond.wait(monitLock, pred);
    }
  
private:
    mutable std::mutex monitMutex;
    mutable std::condition_variable monitCond;
};

template <typename T>                                  // (1)
class ThreadSafeQueue: public Monitor {
public:
    void add(T val){
        lock();
        myQueue.push(val);                             // (6)
        unlock();
        notify_one();
    }
  
    T get(){
        wait( [this] { return ! myQueue.empty(); } );  // (2)
        lock();
        auto val = myQueue.front();                    // (4)
        myQueue.pop();                                 // (5)
        unlock();
        return val;
    }

private:
    std::queue<T> myQueue;                            // (3)
};


class Dice {
public:
    int operator()(){ return rand(); }
private:
    std::function<int()> rand = std::bind(std::uniform_int_distribution<>(1, 6),
                                          std::default_random_engine());
};


int main(){
  
    std::cout << '\n';
  
    constexpr auto NumberThreads = 100;
  
    ThreadSafeQueue<int> safeQueue;                      // (7)

    auto addLambda = [&safeQueue](int val){ safeQueue.add(val);          // (8)
                                            std::cout << val << " "
                                            << std::this_thread::get_id() << "; ";
                                          };
    auto getLambda = [&safeQueue]{ safeQueue.get(); };  // (9)

    std::vector<std::thread> addThreads(NumberThreads);
    Dice dice;
    for (auto& thr: addThreads) thr = std::thread(addLambda, dice());

    std::vector<std::thread> getThreads(NumberThreads);
    for (auto& thr: getThreads) thr = std::thread(getLambda);

    for (auto& thr: addThreads) thr.join();
    for (auto& thr: getThreads) thr.join();
  
    std::cout << "\n\n";
   
}