https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77886
--- Comment #6 from Marc Mutz <marc.mutz at kdab dot com> --- Created attachment 39770 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=39770&action=edit Test case Result: $ g++ -Wextra -std=c++1z -O2 bug.cpp bug.cpp: In function ‘void qt_memfill(T*, T, int) [with T = int]’: bug.cpp:10:20: warning: this statement may fall through [-Wimplicit-fallthrough] case 0: do { *dest++ = value; ^ bug.cpp:12:7: note: here case 7: *dest++ = value; ^~~~ bug.cpp:12:20: warning: this statement may fall through [-Wimplicit-fallthrough] case 7: *dest++ = value; ^ bug.cpp:14:7: note: here case 6: *dest++ = value; ^~~~ bug.cpp:14:20: warning: this statement may fall through [-Wimplicit-fallthrough] case 6: *dest++ = value; ^ bug.cpp:16:7: note: here case 5: *dest++ = value; ^~~~ bug.cpp:16:20: warning: this statement may fall through [-Wimplicit-fallthrough] case 5: *dest++ = value; ^ bug.cpp:18:7: note: here case 4: *dest++ = value; ^~~~ bug.cpp:18:20: warning: this statement may fall through [-Wimplicit-fallthrough] case 4: *dest++ = value; ^ bug.cpp:20:7: note: here case 3: *dest++ = value; ^~~~ bug.cpp:20:20: warning: this statement may fall through [-Wimplicit-fallthrough] case 3: *dest++ = value; ^ bug.cpp:22:7: note: here case 2: *dest++ = value; ^~~~ iow: only the attribute helps.
