https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88097
--- Comment #5 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- As of glibc 2.28, glibc uses __builtin_bswap* when available on all architectures. commit 0d40d0ecba3b1e5b8c3b8da01c708fea3948e193 Author: Joseph Myers <jos...@codesourcery.com> Date: Tue Feb 6 21:55:08 2018 +0000 Unify and simplify bits/byteswap.h, bits/byteswap-16.h headers (bug 14508, bug 15512, bug 17082, bug 20530).