#define USED(...) (void)(__VA_ARGS__)

int main() {
    int a, b, c;
    USED(a, b, c);
}

<source>:5:10: warning: left operand of comma operator has no effect [-Wunused-value]
    5 |     USED(a, b, c);
      |          ^
<source>:1:26: note: expanded from macro 'USED'
    1 | #define USED(...) (void)(__VA_ARGS__)
      |                          ^~~~~~~~~~~
1 warning generated.