Perfect Forwarding Forwards Objects Not Braced Things Trying To Become Objects -- Raymond Chen

By Blog Staff | Aug 25, 2023 02:43 PM | Tags: None

In C++, perfect forwarding is the act of passing a function’s parameters to another function while preserving its reference category. It is commonly used by wrapper methods that want to pass their parameters through to another function, often a constructor.

Perfect Forwarding Forwards Objects, Not Braced Things That Are Trying To Become Objects

By Raymond Chen

From the article:

In C++, perfect forwarding is the act of passing a function’s parameters to another function while preserving its reference category. It is commonly used by wrapper methods that want to pass their parameters through to another function, often a constructor.

template<typename T, typename... Args>
std::unique_ptr<T> make_unique(Args&&... args)
{
    return std::unique_ptr<T>(
        new T(std::forward<Args>(args)...));
}

The make_unique function takes its parameters, forwards them to the T constructor, and then puts the pointer to the newly-constructed T inside a unique_ptr. Those parameters are forwarded perfectly into the constructor: If the original parameters were rvalue reference, then the constructor receives rvalue reference. If the original parameters were lvalue references, then the constructor receives lvalue reference.

But the catch is that it can forward only objects. It can’t forward “braced things that are trying to become objects”.

C++ exceptions and memory allocation failure -- Wu Yongwei

By Wu Yongwei | Aug 24, 2023 10:45 AM | Tags: None

C++ exceptions are habitually disabled in many software projects. A related issue is that these projects also encourage the use of new (nothrow) for fear of exceptions. Is it good practice or bad practice? Also, how likely are we to really encounter out-of-memory errors? I will investigate on this topic and discuss strategies to deal with memory issues.

C++ Exceptions and Memory Allocation Failure

By Wu Yongwei

From the article:

In fact, every time we initialize or modify a string, vector, or map, we may be allocating memory on the heap. If we think that new will end in an exception (and therefore choose to use new (nothrow)), exceptions may also occur when using these mechanisms. In a program that has disabled exceptions, the result will inevitably be a program crash.

Ignoring abnormal scenarios like allocating more memory than the physical memory size at a time (which would likely be a logic error in the program), can a reasonable program still experience memory allocation failures?

Dynamic CUDA with NVIDIA's Runtime Compilation -- Richard Thomson

By Legalize Adulthood | Aug 23, 2023 02:42 PM | Tags: None

Utah C++ Programmers has released a new video:

Dynamic CUDA with NVIDIA's Runtime Compilation

by Richard Thomson

From the video description:

Using CUDA is great way to accelerate tasks on the GPU. Regular CUDA programming compiles your C++ code into code that can execute on the GPU. But what if your problem domain is more dynamic and requires generation of code on the fly?

On the CPU you can use techniques like LLVM to compile code Just-in-Time (JIT) into the native CPU instruction set and call this code directly from your application. What about on the GPU?

The NVRTC (Runtime Compilation) library accepts CUDA C++ source code and creates modules of GPU ready code that you can execute on the GPU.

This month, Richard Thomson will give us an introduction to using the NVRTC library for runtime compilation and nvJitLink for runtime linking of CUDA C++ source code to execute code on the GPU. We'll use a simple fractal generator as the example, with a user provided "iteration formula" to generate a fractal image in the complex plane.

https://www.youtube.com/watch?v=9OCQb5RA-s0

C++23: static operator() and static operator[] -- Sandor Dargo

By Blog Staff | Aug 23, 2023 02:03 PM | Tags: None

In this article, we are going to review two new features of C++23. Now the language allows the call operator (operator()) and the subscription operator (operator[]) to be static.

C++23: static operator() and static operator[]

By Sandor Dargo

From the article:

static operator()

As we saw earlier in our big C++ algorithms tutorial, function objects are extensively used in the standard library to customise the behaviour of several functions. With the introduction of ranges in C++20 (and of earlier non-standard libraries), the usage of function objects became even more widespread.

Many function objects are extremely simple. Let’s take an implementation of isEven.

auto isEven = [](int i) {return i % 2 == 0;};

2023-08 Mailing Available

By Administrator | Aug 23, 2023 09:54 AM | Tags: None

The 2023-08 mailing of new standards papers is now available.

CopperSpice: Template Parameters

By Ansel Sermersheim | Aug 22, 2023 11:31 AM | Tags: None

New video on the CopperSpice YouTube Channel:

Template Parameters

by Barbara Geller and Ansel Sermersheim

About the video:

Do you know the precise difference between a parameter and an argument? Where can a default argument appear for a template parameter? We have some answers in our newest C++ video.

Please take a look and remember to subscribe.

Using GitHub Actions for Continuous Integration -- Richard Thomson

By Legalize Adulthood | Aug 21, 2023 02:34 PM | Tags: None

Utah C++ Programmers has released a new video:

Using GitHub Actions for Continuous Integration

by Richard Thomson

From the video description:

GitHub actions allow you to set up continuous integration for your C++ project. You can configure, build and test your code in a variety of operating systems and hardware configurations.

This month, Richard Thomson will give us an introduction to GitHub actions for continuous integration of C++ projects. We'll look at how to set up automatic building and testing of code on various repository events, such as commits, pull requests, and so-on.

Some of the topics we will cover are:

• How to configure GitHub actions from scratch
• How to use some continuous integration project templates
• How to run tests
• How to integrate custom build/test environments

https://www.youtube.com/watch?v=1q8BQtvr8sY

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C++23: Syntactic Sugar with Deducing This -- Rainer Grimm

By Blog Staff | Aug 21, 2023 01:57 PM | Tags: None

The Curiously Recurring Template Pattern (CRTP) is a heavily used idiom in C++. It is similarly resistant to understanding as the classic design pattern visitor I presented in my last post: “C++23: Deducing This“.  Thanks to deducing this, we can remove the C and R from the abbreviation.

C++23: Syntactic Sugar with Deducing This

By Rainer Grimm

From the article:

CRTP

The acronym CRTP stands for the C++ idiom Curiously Recurring Template Pattern and denotes a technique in C++ in which a class Derived is derived from a class template Base. The critical point is that Base has Derived as a template argument.

template <typename T>
class Base{
    ...
};

class Derived : public Base<Derived>{
    ...
};

CRTP is typically used to implement static polymorphism. Unlike dynamic polymorphism, static polymorphism happens at compile time and does not require an expensive run-time pointer indirection.

Introduction to Programming with C++ For Engineers, Book Review -- Bartlomiej Filipek

By Bjarne Stroustrup | Aug 18, 2023 01:52 PM | Tags: None

Lots of practical examples, general programming, software development techniques, OOP, parallel algorithms, plus C++ to combine it all into working applications. This is a short introduction to the book “Introduction to Programming with C++” by Prof. Boguslaw Cyganek, an excellent book for students who start their journey with system coding.

Introduction to Programming with C++ For Engineers, Book Review

By Bartlomiej Filipek

From the review:

“I have been highly impressed by Introduction to Programming with C++ for Engineers and can’t recommend it enough. With its content designed keeping in mind the author’s own students, the book assumes no prior programming experience, making it an excellent choice for anyone who wishes to learn C++ as their first programming language. […]
The book extends its reach beyond just the programming language, shedding light on aspects such as microprocessor operations, software development processes, UML, and more. Furthermore, the appendices cover essential tools like CMake and Git, making this book a comprehensive guide for anyone delving into C++ programming. The detailed content, careful attention to detail, and clarity in explaining concepts have garnered much praise for the book. This makes it an invaluable resource for those aspiring to learn and understand modern C++ programming."

Let's Enumerate the UB -- Shafik Yaghmour

By Blog Staff | Aug 16, 2023 01:46 PM | Tags: None

Some time ago I started working on P1705 Enumerating Core Undefined Behavior, I have collected a large set of undefined behavior (UB) during that time. There is going to be a lot of work involved in getting the annex into shape and editing it into the standard. While this work is ongoing, I will take some time to write blog posts to explore the set of undefined behaviors.

Let's Enumerate the UB

By Shafik Yaghmour

From the article:

In these posts I will cover: why we have each undefined behavior, some consequences of running afoul of each UB and tools we can use to catch UB. My plan is to enumerate them in the order they appear in the standard.

IFNDR (What is that?)

Before we go on, let’s talk about a term we find in the standard, ill-formed no diagnostic required; also known as IFNDR. This is like undefined behavior in that the standard places no requirements on a program that contains IFNDR constructs, see [intro.compliance.general]p2.2 which says (emphasis mine):

If a program contains a violation of a rule for which no diagnostic is required, this document places no requirement on implementations with respect to that program.

compared to the defintion of undefined behavior which says:

behavior for which this document imposes no requirements

The main difference is that IFNDR is a static property of your code (it is a propety of the program).