https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83773
--- Comment #2 from Eric Gallager <egallager at gcc dot gnu.org> ---
Clang calls it -Wmacro-redefined:
$ clang -fdiagnostics-show-option -Wall -c 83773.c
83773.c:2:9: warning: 'AAA' macro redefined [-Wmacro-redefined]
#define AAA 2
^
83773.c:1:9: note: previous definition is here
#define AAA 1
^
1 warning generated.
$
