Implement the C++ Standard Library: Design, Optimisations, Testing while Implementing Libc++

https://cppcon.org​
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Implement the C++ Standard Library: Design, Optimisations and Testing while Implementing Libc++ - Hui Xie - CppCon 2025
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This presentation covers various practical examples in the designs, optimisations and testing in libc++, a standard library implementation.

In space optimisation section, it presents various examples of using compact type, reusing tail padding bytes, reusing unused bits in existing bytes, in various standard types: std::stop_token , std::expected , std::optional , std::variant , std::ranges library and std::move_only_function .

In time optimisations section, it presents examples of how we optimise std::atomic＜T＞::wait 's waiting strategy, how we optimised algorithms for segmented iterators, and also how we keep in mind optimisations by leaving the door open for future optimisations. At the same time, compilation time is also important so it also contains examples how unnecessary template instantiations can be avoided.

Finally, this talk covers the unit tests of libc++, including the high test coverage of standard spec, the technique we share tests between runtime and constexpr, negative testing and so on.

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Slides: https://github.com/CppCon/CppCon2025/...

Video Sponsored by Susquehanna -    / @lifeatsusquehanna  
Sponsored by JetBrains: https://www.jetbrains.com/clion/
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Hui Xie

Hui Xie is a C++ software developer at Qube Research and Technologies in the finance industry. He is a member of the standard committee WG21 and the UK national body BSI. He usually contributes to the ranges study group SG9. He is also an active contributor to libc++, the clang's standard library implementation.
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