De-fragmenting C++: Making Exceptions and RTTI More Affordable and Usable

by Herb Sutter

A fundamental reason why C++ is successful and loved is its adherence to Stroustrup’s zero-overhead principle: You don’t pay for what you don’t use, and if you do use a feature you can’t reasonably code it better by hand. In the C++ language itself, there are only two features that violate the zero-overhead principle, exception handling and RTTI – and, unsurprisingly, these are also the only two C++ language features that every C++ compiler has switches to turn off and that are regularly discouraged or even banned. This matters because not using these features is the largest current cause of fragmentation of the C++ community into incompatible dialects, and the cause of recurring problems including type confusion security vulnerabilities arising from “didn’t down-cast using dynamic_cast because that would be too slow.” This talk is about ongoing long-term efforts to try to unify the community in this area, not by replacing exceptions and RTTI, but by doubling down: fully embracing exceptions and RTTI, and improving them so they can be zero-overhead too.

Better Code: Relationships

by Sean Parent

Computer scientists are bad at relationships. Nearly every program crash is rooted in a mismanaged relationship, yet we spend most of our time discussing types and functions and not the relationships connecting them together. This talk looks at common ways data and code are connected in an application, how those relationships are typically represented, and the problems caused by the use, and misuse of these paradigms. Then we'll look at ways to model these relationships in C++ and use them to build correct applications.

CppCon 2019 Trip Report

by Matt Godbolt

I’m on my way back from the 2019 CppCon conference and my head is buzzing with ideas! What an amazing experience!

Applied WebAssembly: Compiling and Running C++ in Your Web Browser

by Ben Smith

WebAssembly is a new technology in all modern browsers designed to let you run high-performance code. Maybe you've heard of WebAssembly before, read an article or two, or even tried to use it with your software project. Since WebAssembly is a low-level language, it's easy to get bogged down in the technical details, and leave without knowing whether WebAssembly will be useful for you. In this talk, I'll take a top-down approach, showing a real problem and how WebAssembly can help.

From August to December this year, I'll be teaching C++ to students at Morehouse College. Having a tool like Compiler Explorer is invaluable as a teaching aid, since it allows the students to immediately see C++ compilation results, on any device that has a web browser. But Compiler Explorer and tools like it require a server to do compilation, so they're hard to use offline. With WebAssembly, we can run the compiler client-side, in the browser, no server required.

First, I'll show how I ported the clang compiler and linker to WebAssembly. Since Clang 8 supports WebAssembly as a compilation target, we can even run the resulting executable sandboxed in the browser. Next, we'll dive into how Clang compiles C++ constructs into WebAssembly. Finally, we'll look at some of the new WebAssembly features in development.

Speed Is Found In The Minds of People

by Andrei Alexandrescu

In all likelihood, sorting is one of the most researched classes of algorithms. It is a fundamental task in Computer Science, both on its own and as a step in other algorithms. Efficient algorithms for sorting and searching are now taught in core undergraduate classes. Are they at their best, or is there more blood to squeeze from that stone? This talk will explore a few less known – but more allegro! – variants of classic sorting algorithms. And as they say, the road matters more than the destination. Along the way, we'll encounter many wondrous surprises and we'll learn how to cope with the puzzling behavior of modern complex architectures.

Back to Basics at CppCon 2019

by Arthur O’Dwyer

Tomorrow I’ll be flying out to Denver, Colorado, for CppCon 2019. This will be my busiest CppCon yet! Besides giving my “STL From Scratch” weekend course for the third year in a row, this year I’m also the chair of CppCon’s new “Back to Basics” track...

Nano-coroutines to the Rescue! (Using Coroutines TS, of Course)

by G. Nishanov

Are you doing memory lookups in a huge table?
Does your embarrassingly random access to your lookup tables lead to memory stalls?

Fear no more!

We will explore techniques that allow us to do useful work while the prefetcher is busily working on bringing the requested cache lines from main memory, by utilizing nano-coroutines.

And the best part, nano-coroutines can be easily implemented using Coroutines TS that is already available in MSVC and Clang compilers. With a little bit of library support we can utilize the coroutines to extract intra-thread parallelism and quadruple the speed up your lookups.

Tool Time 2019

by Jon Kalb

Similar to tech labs at some other events, we’re offering the opportunity for anyone, from an author/creator, to a vendor, to a super-user, to represent a tool (app, library, framework, or service) and run their own table answering questions or showing demos...

Highlighting the Student and Support Tickets for Meeting C++ 2019

by Jens Weller

With the Schedule for Meeting C++ 2019 being complete regarding submitted talks, I want to highlight, that there is an opportunity for folks to attend the conference with a free ticket!

Modern C++ Design (part 1 of 2)

Modern C++ Design (part 2 of 2)

by Titus Winters

The old rules for C++API design are due for an update - we have made ad hoc changes to design principles in the standard library, but haven’t really written down the new ideas. Parameter passing and API design for free functions/member functions is due for a general update, particularly as a result of rvalue-references and reference qualification. How do we pass non-owning references? How do we sink a T? How do we express “maybe move” APIs? When do we want reference-qualified overload sets? What does an rvalue-reference qualified non-overloaded method mean? How do we express call once semantics?

For types, our consistency in producing Regular types has weakened in recent C++ releases with types like unique_ptr (move-only) and string_view (reference semantics). These classes of design that have shown themselves to be valuable, but certainly surprising at first. As we should not continue to extend the set of type designs arbitrarily, this is a good time to look at type design in the modern C++ era and narrow down the set of designs that are generally favored. This talk will focus on modern C++ design from small (choice of passing by value or reference) to large (Regular types, reference types, move-only types, etc). We will also introduce a taxonomy of type properties as a means to discuss known-good type design families.

We will also dive into the discussion of whether Regular design covers all good design, or whether there is more to the story.