https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82318
--- Comment #3 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> --- (In reply to Andrew Pinski from comment #1) > This is interesting because log2 should have already done a rounding to > double before returning. I suppose that if the C library has been built with GCC without -fexcess-precision=standard (explicitly or implied), then this rounding is not done. I've done my tests on a Debian/unstable machine (currently glibc 2.24).