core: split out event code

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/utils.h

@@ -30,6 +30,9 @@ safe_isnan(double a) {
 	return isnan(a);
 }
 
+#define CASESTRRET(s)                                                                    \
+	case s: return #s
+
 /// Same as assert false, but make sure we abort _even in release builds_.
 /// Silence compiler warning caused by release builds making some code paths reachable.
 #define BUG()                                                                            \