Registration is now open for CppCon 2022, which starts on September 11 and will again be held both in person and online. To whet your appetite for this year’s conference, we’re posting videos of some of the top-rated talks from last year’s conference. Here’s another CppCon talk video we hope you will enjoy – and why not register today for CppCon 2022 to attend in person, online, or both!

Implementing C++ Modules: Lessons Learned, Lessons Abandoned

by Cameron DaCamara & Gabriel Dos Reis

Summary of the video:

C++ Modules were designed to bring more safety to your programs, while dramatically reducing compile time, resulting in overall increased productivity. How can your C++ toolchain meet this challenge? What can you do to take advantage of these new functionalities available in your toolbox? In this talk, we share lessons learned from implementing Modules based on the singular idea of providing robust support through the entire toolchain (from the lexer through the linker, the IDE, the build system, etc.), debunking the misconception that C++ Modules are just some syntactic sugar that is compiled away by the front-end. The challenges that any C++ compiler implementer faces include: (1) how to satisfy the requirements of merging materialization of declarations -- needed for sound handling of the global module fragments, in particular, as found in header files and header units – with associated performance cost; (2) how to take advantage of the One Definition Rule guarantees provided by named modules. They must address those challenges without compromising efficiency and static semantics. These lessons are valuable not just to C++ tools developers, but to ordinary C++ programmers as well, shedding light on how speed and safety gains are achieved by staying close to the spirit of the original C++ Modules design (“take the ODR as foundational”), and how you can put them to good use in the architecture of your programs and libraries.