Oddly enough, this wasn't actually having any effect. Apparently it's
legitimate to pass empty arguments to function-like macros. But this
wasn't the intention here. I had intended for this macro to never
accept any argument.
SWITCH_METRICS_OP (op);
/* Switch back to metrics operation saved by SAVE_THEN_SWITCH_METRICS_OP */
SWITCH_METRICS_OP (op);
/* Switch back to metrics operation saved by SAVE_THEN_SWITCH_METRICS_OP */
-#define RESTORE_METRICS_OP(op) \
+#define RESTORE_METRICS_OP() \
SWITCH_METRICS_OP (save);
void
SWITCH_METRICS_OP (save);
void