gc.c: add red (persistent no scan) color in the comment [ci skip]
@@ -193,7 +193,7 @@ gettimeofday_time(void)
#define GC_STEP_SIZE 1024
-/* white: 001 or 010, black: 100, gray: 000 */
+/* white: 001 or 010, black: 100, gray: 000, red:111 */
#define GC_GRAY 0
#define GC_WHITE_A 1
#define GC_WHITE_B (1 << 1)
