diff --git a/nemu/scripts/build.mk b/nemu/scripts/build.mk
index 1ff0ae8..51350e8 100644
--- a/nemu/scripts/build.mk
+++ b/nemu/scripts/build.mk
@@ -40,16 +40,6 @@ $(OBJ_DIR)/%.o: %.cc
 	@$(CXX) $(CFLAGS) $(CXXFLAGS) -c -o $@ $<
 	$(call call_fixdep, $(@:.o=.d), $@)
 
-$(OBJ_DIR)/%-lex.l: %-exp.y
-	@echo + YACC $<
-	@mkdir -p $(dir $@)
-	@$(YACC) $(YFLAGS) -H $(<:.y=.h) -o $@ $<
-
-$(OBJ_DIR)/%.c: %-lex.l
-	@echo + LEX $<
-	@mkdir -p $(dir $@)
-	@$(LEX) $(LFLAGS) -o $@ $<
-
 # Depencies
 -include $(OBJS:.o=.d)
 
diff --git a/nemu/src/monitor/sdb/sdb.c b/nemu/src/monitor/sdb/sdb.c
index 210fe1a..b1e3ae0 100644
--- a/nemu/src/monitor/sdb/sdb.c
+++ b/nemu/src/monitor/sdb/sdb.c
@@ -26,6 +26,8 @@
 
 static int is_batch_mode = false;
 
+extern int yyparse(void);
+
 // command handlers
 static int cmd_help(char *args);
 static int cmd_c(char *args);
@@ -284,6 +286,8 @@ 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);