https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103848
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Jakub Jelinek from comment #3) > Other options perhaps could be - (__x._M_node ? 1 : 0) That produces worse code (with a jump) at -O1 > or - 1 + !__x._M_node Isn't that undefined for (x - y - 1 + !x) if x and y are both null? We get (T*)0 - 1 + 1 which overflows twice. > or - !!__x._M_node I think that's what I'll go with, thanks.