https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115273
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Note ubsan can detect (correctly) a different undefined behavior since GCC 13 (since r13-4988-g8692b15ae7c05e; aka PR108256) but the undefinedness of passing 0 to ctz is still not detected and that is a dup of bug 115127 .
