diff --git a/nemu/src/monitor/sdb/addrexp.l b/nemu/src/monitor/sdb/addrexp.l
index cb7dea4..137d042 100644
--- a/nemu/src/monitor/sdb/addrexp.l
+++ b/nemu/src/monitor/sdb/addrexp.l
@@ -5,8 +5,8 @@
 
 %%
 
-0[xX][0-9a-fA-F]+ { yylval = strtol(yytext, NULL, 16); return HEX_NUMBER; }
-[0-9]+            { yylval = atoi(yytext); return NUMBER; }
+0[xX][0-9a-fA-F]+ { yylval = strtoul(yytext, NULL, 16); return HEX_NUMBER; }
+[0-9]+            { yylval = strtoul(yytext, NULL, 10); return NUMBER; }
 [+\-*/()]         { return *yytext; }
 [ \t]             {  }
 .                 { printf("Unexpected character: %s\n", yytext); }
diff --git a/nemu/src/monitor/sdb/addrexp.y b/nemu/src/monitor/sdb/addrexp.y
index e4fc777..d0dc734 100644
--- a/nemu/src/monitor/sdb/addrexp.y
+++ b/nemu/src/monitor/sdb/addrexp.y
@@ -4,7 +4,7 @@
     #include <stdint.h>
     extern int yylex(void);
     void yyerror(uint32_t *result, const char *err) {
-        // fprintf(stderr, "Error: %s\n", err);
+      fprintf(stderr, "Error: %s\n", err);
     }
 %}