MSVC C++23: constexpr cmath with LLVM Libc

This article discusses the implementation of constexpr math functions in C++23 as part of MSVC's experimental features. It highlights the changes made to the standard library and invites user feedback on the new functionality.

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Proposal P0533R9 made numerous math functions in the standard library compile-time evaluable in C++23. Implementing the feature required a good bit of time and effort, but MSVC is preparing its experimental implementation for the 14.52 build tools (compiler version 19.52)! We are still refining the feature, so expect the dust to settle only when this has shipped for production.

The feature is enabled with a combination of the /std:c++23 or later and /Zc:cmath compiler options. It is initially shipping as experimental and off by default because our implementation is powered by a new math library at compile-time and runtime, which can change performance and accuracy characteristics for existing programs. Our aim is to collect user feedback before making decisions about default behaviors…

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