https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63352
--- Comment #20 from Richard PALO <richard at netbsd dot org> --- >From what I've been able to gather, 'f' precision 17 & 18 incorrectly terminate with a '2' where they seemingly need be '1' and '5' respectfully (along with corresponding 'e' with precision 16 & 17). The default rounding is FE_TONEAREST on illumos. The other modes seem okay. Therefore I filed https://www.illumos.org/issues/5224 (with an updated version of the test program). BTW, on a sidenote, with the test program on NetBSD (6.1) I notice that rounding mode seems to be completely ignored. Does gnu-c runtime expect correct behaviour? (NB I made a version of the test program to avoid any constant 1.0/3.0 being used)... It would be interesting to know about other platforms... I came across a sourceware bug where this was supposedly fixed (https://sourceware.org/bugzilla/show_bug.cgi?id=5044)