Implement the C++ Standard Library - Design, Optimizations, and Testing while Implementing Libc++

Explore practical approaches to implementing the C++ Standard Library through real-world examples from the libc++ project in this conference talk from CppCon 2025. Discover space optimization techniques including compact type usage, tail padding byte reuse, and unused bit utilization across standard types like std::stop_token, std::expected, std::optional, std::variant, std::ranges library, and std::move_only_function. Learn time optimization strategies covering std::atomic::wait waiting mechanisms, algorithm optimizations for segmented iterators, and forward-thinking design approaches that preserve future optimization opportunities while managing compilation time through reduced template instantiations. Examine comprehensive unit testing methodologies for libc++ including high test coverage of standard specifications, shared testing techniques between runtime and constexpr contexts, and negative testing approaches. Gain insights from an active libc++ contributor and WG21 standard committee member who brings practical experience from both industry development and standard library implementation work.