C++20 Coroutines

by Martin Bond

There seems to be a lot of confusion around the implementation of C++20 coroutines, which I think is due to the draft technical specification for C++20 stating that coroutines are a work in progress so we can’t expect full compiler and library support at this point in time.

A lot of the problems probably arise from the lack of official documentation about working with coroutines. We have been given C++ syntax support for coroutines (the co_yield and co_return) but without all of what I consider full library support. The standard library has hooks and basic functionality for supporting coroutines, but we must incorporate this into our own classes. I anticipate that there will be full library support for generator style coroutines in C++23.

The C++20 specification is obviously looking to provide support for parallel (or asynchronous) coroutines using co_await, which makes the implementation of a simpler generator style synchronous coroutines more complex. The implementation requirements for our coroutines utilises a Future and Promise mechanism similar to the std::async mechanism for asynchronous threads.

If you are a Python or C# developer expecting a simple coroutine mechanism, you’ll be disappointed because the C++20 general purpose framework is incomplete. Having said that, there are many blogs and articles on the web that include a template class that supports generator style coroutines. This blog contains a usable coroutine template and example code after discussing what a coroutine is...

C++20 Concepts — Complete Guide

by Šimon Tóth

One of the well deserved common complaints about C++ is the low quality of compiler errors. Both GCC and Clang made a lot of progress to improve the situation in the past 10 years, but templated code is one area where they can’t really help...

From Variadic Templates to Fold Expressions

by Rainer Grimm

In my last two posts "Variadic Templates or the Power of Three Dots" and "More about Variadic Templates", I introduced variadic templates. This post goes one step further in the future and presents fold expressions that can directly reduce a parameter pack with a binary operator...

Design Patterns VS Design Principles: Iterator, Mediator and Memento

by Jonathan Boccara

In our objective to understand how the GoF design patterns relate to the GRASP design principles, we’re going to analyse 3 more Behavioural patterns today: Iterator, Mediator and Memento...

Coercing deep const-ness

by Barry Revzin

In C++, template deduction doesn’t allow for any conversion. A type matches the pattern, or it’s a deduction failure. But there’s one sort-of exception to this rule, and it’s an exception that everyone has taken advantage of...

C++20 Modules: Private Module Fragment and Header Units

by Rainer Grimm

In the last weeks; I learned something new about modules in C++20: private modules fragments and header units. Consequently, I make a short detour in this post and present these new features...

C++20 Modules — Complete Guide

by Šimon Tóth

Compilers and build systems are slowly starting to support C++20 modules. Perfect time for you to read this guide and benefit from the massive compilation speedups. This article reflects the state as of September 2021...

Ordering asynchronous updates with coroutines, part 1, part 2, part 3, part 4, part 5

by Raymond Chen

I opined some time ago on the perils of holding a lock across a coroutine suspension point. But say you have a bunch of asynchronous activity that you want to serialize. How can you do that without a lock?

There are a few different scenarios in which you may need to protect asynchronous activity. We’ll look at them over the next few days...

Choosing Hubilo as an online platform for Meeting C++ 2021

by Jens Weller

During July and August I did compare many online platforms, to choose the one to host this years online conference and the events of Meeting C++ online in. The winner is Hubilo.

Its been a difficult and time consuming process to compare the various platforms and get a feel for what online events will have a look and feel in 21/22 when choosing a certain platform. I'd like to be able to host all formats of the online User Group in one platform: the talks, the panels and especially the online fairs for C++ jobs/recruiting and tooling. This years conference will host all these event types too!

C++ User Group Meetings in September 2021

by Jens Weller

The monthly overview about upcoming C++ User Group Meetings in September. As the pandemic ends or continues, depending in which part of the world you live, I list again all meetings online and real world.

Meeting C++ online hosts two events in September:

Meeting C++ is still looking for employers to participate in the online job fair, register your spot with in the next days to be best visible for this event.