diff --git a/nemu/scripts/build.mk b/nemu/scripts/build.mk
index 0a04409..07c3c79 100644
--- a/nemu/scripts/build.mk
+++ b/nemu/scripts/build.mk
@@ -42,13 +42,11 @@ $(OBJ_DIR)/%.o: %.cc
 
 $(OBJ_DIR)/%.tag.c: %.y
 	@echo + YACC $<
-	@echo $@ $<
 	@mkdir -p $(dir $@)
 	@$(YACC) $(YFLAGS) --header=$(<:.y=.h) -o $@ $<
 
 $(OBJ_DIR)/%.yy.c: %.l $(OBJ_DIR)/%.tag.c
 	@echo + LEX $<
-	@echo $@ $<
 	@mkdir -p $(dir $@)
 	@$(LEX) $(LFLAGS) -o $@ $<
 
diff --git a/nemu/src/monitor/sdb/filelist.mk b/nemu/src/monitor/sdb/filelist.mk
index bad7396..394a8a3 100644
--- a/nemu/src/monitor/sdb/filelist.mk
+++ b/nemu/src/monitor/sdb/filelist.mk
@@ -1,13 +1,3 @@
 SRCS-y += src/monitor/sdb/addrexp.tag.c src/monitor/sdb/addrexp.yy.c
 INC_PATH += src/monitor/sdb
 LFLAGS += -DYY_NO_UNPUT -DYY_NO_INPUT
-
-$(BUILD_DIR)/src/monitor/sdb/addr-exp.c: src/monitor/sdb/addr-exp.y
-	@echo + YACC $<
-	@mkdir -p $(dir $@)
-	@$(YACC) $(YFLAGS) --header=$(<:.y=.h) -o $@ $<
-
-$(BUILD_DIR)/src/monitor/sdb/addr-lex.c: src/monitor/sdb/addr-lex.l $(BUILD_DIR)/src/monitor/sdb/addr-exp.c
-	@echo + LEX $<
-	@mkdir -p $(dir $@)
-	@$(LEX) $(LFLAGS) -o $@ $<
diff --git a/nemu/src/monitor/sdb/sdb.c b/nemu/src/monitor/sdb/sdb.c
index b1e3ae0..23218d5 100644
--- a/nemu/src/monitor/sdb/sdb.c
+++ b/nemu/src/monitor/sdb/sdb.c
@@ -286,8 +286,6 @@ void sdb_mainloop() {
     cmd_c(NULL);
     return;
   }
-  // int res = yyparse();
-  // exit(res);
 
   for (char *str; (str = rl_gets()) != NULL;) {
     char *str_end = str + strlen(str);