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Quick Q: What are copy elision and return value optimization?

By Adrien Hamelin | Aug 5, 2019 12:42 PM | Tags: basics

Quick A: optimisation compilers are allowed to do for perfomance.

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What are copy elision and return value optimization?

Copy elision is an optimization implemented by most compilers to prevent extra (potentially expensive) copies in certain situations. It makes returning by value or pass-by-value feasible in practice (restrictions apply).

It's the only form of optimization that elides (ha!) the as-if rule - copy elision can be applied even if copying/moving the object has side-effects...

Enabling Polymorphism in SYCL using the C++ idiom "Curiously Recurring Template Pattern"

By rodburns | Aug 1, 2019 11:43 PM | Tags: None

Dynamic polymorphism is a widely used C++ feature that allows code to be more flexible, and helps create easily extendable interfaces by overriding the base class specified interfaces inside our derived classes. However, in SYCL kernel code in order to emulate dynamic polymorphism we need to use some curious tricks and techniques.

Enabling Polymorphism in SYCL using the C++ idiom "Curiously Recurring Template Pattern"

by Georgi Mirazchiyski

From the article:

The CRTP idiom offers an alternative approach to polymorphism by providing us with the ability to specify static interfaces, where the base class specifies the the structure of the interface, while the derived one represents the implementation. In this case, the base class does represent the interface and the derived class represents the implementation — similar to the general idea of polymorphism.

Why Static Analysis Can Improve a Complex C++ Codebase

By Andrey Karpov | Jul 30, 2019 10:23 AM | Tags: static code analysis static analysis sast legacy code code quality

Gradually and imperceptibly we get the situation when C++ projects’ complexity becomes extreme. Unfortunately, now a C++ programmer can’t be on his own.

Why Static Analysis Can Improve a Complex C++ Codebase

by Andrey Karpov

From the article:

Analyzers know more than even professional developers. It has become too difficult to take into account and remember all the nuances when writing code. For instance, if you haven’t specifically read about it, you’ll never guess that calls to memset function for clearing private data sometimes disappear, as from a compiler’s point of view, a call to memset function is redundant. Meanwhile, it is a serious security defect CWE-14 that is detected literally everywhere.

Comparisons in C++20--Barry Revzin

By Adrien Hamelin | Jul 29, 2019 10:29 AM | Tags: experimental

Get familiar with it, it's coming and it's going to help you!

Comparisons in C++20

by Barry Revzin

From the article:

Now that the Cologne meeting is over and we’ve more or less finalized (at least before the NB comments come in) C++20, I wanted to take the time to describe in detail one of the new language features we can look forward to. The feature is typically referred to as operator<=> (defined in the language as “three-way comparison operator” but more colloquially referred to as “operator spaceship”), but I think it has broader scope than that.

We’re not just getting a new operator, we’re significantly changing the semantics of how comparisons work at a language level...

Trip Report: C++ Standards Meeting in Cologne, July 2019--Botond Ballo

By Adrien Hamelin | Jul 26, 2019 12:51 PM | Tags: community

Lots happened!

Trip Report: C++ Standards Meeting in Cologne, July 2019

by Botond Ballo

From the article:

Last week I attended a meeting of the ISO C++ Standards Committee (also known as WG21) in Cologne, Germany. This was the second committee meeting in 2019; you can find my reports on preceding meetings here (February 2019, Kona) and here (November 2018, San Diego), and previous ones linked from those. These reports, particularly the Kona one, provide useful context for this post...

How To Detect Function Overloads in C++17, std::from_chars Example

By bfilipek | Jul 24, 2019 01:35 AM | Tags: None

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How To Detect Function Overloads in C++17, std::from_chars Example

by Bartlomiej Filipek

From the article:

Working with real examples is better in most of the cases, so I like that we could show how the detection pattern works on a real function: std::from_chars. The full check used various of techniques: SFINAE, void_t, decltype, std::declval, std::true_type, std::false_type and partial template specialisation. Plus we even used if constexpr!

What Every C++ Developer Should Know to (Correctly) Define Global Constants--Jonathan Boccara

By Adrien Hamelin | Jul 23, 2019 11:50 AM | Tags: intermediate c++17

C++17 to the rescue.

What Every C++ Developer Should Know to (Correctly) Define Global Constants

by Jonathan Boccara

From the article:

Constant values are an everyday tool to make code more expressive, by putting names over values.

For example, instead of writing 10 you can write MaxNbDisplayedLines to clarify your intentions in code, with MaxNbDisplayedLines being a constant defined as being equal to 10.

Even though defining constants is such a basic tool to write clear code, their definition in C++ can be tricky and lead to surprising (and even, undefined) behaviour, in particular when making a constant accessible to several files.

Everything in this article also applies to global variables as well as global constants, but global variables are a bad practice contrary to global constants, and we should avoid using them in the first place...

std::format in C++20--Victor Zverovich

By Adrien Hamelin | Jul 23, 2019 11:38 AM | Tags: experimental community

Just great!

std::format in C++20

by Victor Zverovich

From the article:

I’m happy to announce that the Text Formatting proposal (std::format) made it into the C++20 Committee Draft at the Cologne meeting, just in time before the feature freeze. This concludes a three-year long design, implementation, and standardization effort.

Here’s a brief history of the proposal aka “what took you so long?”...