Seems like since C++26, it does use constexpr https://en.cppreference.com/w/cpp/numeric/math/sqrt

My understanding is that all of the functions found in the C compatibility headers that the C++ standard defines can not be made constexpr. sqrt is among them, as are a lot of the math functions.

The compatibility can be solved with macros to toggle it on or off depending on how you're building. C++26 has constexpr sqrt.

There is a paper suggesting to replace all macro based code, due to way modules work.

https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p26...