MSVC is experimenting with correctly-rounded math (LLVM libc)

Since 2015, the math functions in cmath and cstdlib are supplied by the C runtime via math.h and stdlib.h, which Microsoft ships as part of the Universal C Runtime (UCRT). … In the modern day, the UCRT math functions have known mathematical inaccuracies. See Accuracy of Mathematical Functions in Single, Double, Double Extended, and Quadruple Precision by Gladman, et al. for more info (it’s hot off the press). These inaccuracies stem from implementations that are quite old, dating to times whe...