https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120901
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Note with -O2 -W -Wall we do get an uninitialized variable warning even: <source>:8:18: warning: 'argc.0' is used uninitialized [-Wuninitialized] 8 | struct c a; | ^ <source>:6:9: note: 'argc.0' was declared here 6 | }; | ^