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Conditional Members--Barry Revzin

By Adrien Hamelin | Nov 30, 2021 02:03 PM | Tags: c++20 advanced

Did you feel the need?

Conditional Members

by Barry Revzin

From the article:

I’d previously written a post about if constexpr (and how it’s not broken). I argued in that post how, broadly speaking, C++20 gives you the tools to solve the problems you want, even if they work a bit differently to D’s static if (with one notable exception, which this post greatly expands on). Now, over the past couple years, I’ve been working on a project that really is a deep dive into what Andrei calls “Design by Introspection.” This approach (for lack of a better definition), relies on conditioning functionality based on template parameters...

C++20: Heterogeneous Lookup in (Un)ordered Containers--Bartlomiej Filipek

By Adrien Hamelin | Nov 28, 2021 11:45 PM | Tags: performance

Did you know?

C++20: Heterogeneous Lookup in (Un)ordered Containers

by Bartlomiej Filipek

From the article:

Would you like to gain 20…35 or even 50% speed improvements when searching in associative containers? In this blog post, we’ll explore a technique called “heterogenous access” that offers such impressive speedups. We’ll explore ordered containers, and the support for unordered collections added recently in C++20...

Virtual function calls in constructors and destructors

By Andrey Karpov | Nov 27, 2021 01:38 AM | Tags: virtual functions pitfalls code analyzers

In different programming languages, the behavior of virtual functions differs when it comes to constructors and destructors. Incorrect use of virtual functions is a classic mistake. Developers often use virtual functions incorrectly. In this article, we discuss this classic mistake.

Virtual function calls in constructors and destructors

by Andrey Karpov

From the article:

So, what's the problem? You can find this information in any C++ programming book. The problem is that it's easy to forget about it! Thus, some programmers assume that foo and bar functions are called from the most derived C class. People keep asking the same question on forums: "Why does the code run in an unexpected way?" I think now you understand why it's easy to make a mistake in such code. Especially if you write code in other languages where the behavior is different. Let's look at the code fragment in C#.

Three reasons to pass std::string_view by value--Arthur O’Dwyer

By Adrien Hamelin | Nov 12, 2021 01:14 PM | Tags: performance

You should.

Three reasons to pass std::string_view by value

by Arthur O’Dwyer

From the article:

It is idiomatic to pass std::string_view by value. Let’s see why.

First, a little background recap. In C++, everything defaults to pass-by-value; when you say Widget w you actually get a whole new Widget object. But copying big things can be expensive. So we introduce “pass-by-const-reference” as an optimization of “pass-by-value,” and we tell people to pass big and/or expensive things like std::string by const reference instead of by value.

But for small cheap things — int, char*, std::pair<int, int>, std::span<Widget> — we continue to prefer the sensible default behavior of pass-by-value.

Pass-by-value has at least three performance benefits over pass-by-(const)-reference. I’ll illustrate all three of them via string_view...