diff --git a/demos/scripts/reqdemo.sh b/demos/scripts/reqdemo.sh
index d348d2b3..e7bc89dd 100755
--- a/demos/scripts/reqdemo.sh
+++ b/demos/scripts/reqdemo.sh
@@ -1,5 +1,7 @@
 #!/bin/bash -x
 
+set -e
+
 # generate self-signed CA certificate
 gmssl sm2keygen -pass 1234 -out cakey.pem -pubout pubkey.pem
 gmssl certgen -C CN -ST Beijing -L Haidian -O PKU -OU CS -CN CA -days 365 -key cakey.pem -pass 1234 -out cacert.pem
@@ -24,3 +26,17 @@ gmssl reqsign -in alicereq.pem -days 365 -key_usage digitalSignature -cacert cac
 gmssl certparse -in alicecert.pem
 
 
+rm -fr pubkey.pem
+rm -fr cacert.pem
+rm -fr signkey.pem
+rm -fr signreq.pem
+rm -fr signcert.pem
+rm -fr enckey.pem
+rm -fr encreq.pem
+rm -fr enccert.pem
+rm -fr alicekey.pem
+rm -fr alicepubkey.pem
+rm -fr alicereq.pem
+rm -fr alicecert.pem
+
+echo ok
diff --git a/src/asn1.c b/src/asn1.c
index ac93fd9e..86c37c54 100644
--- a/src/asn1.c
+++ b/src/asn1.c
@@ -1334,9 +1334,12 @@ int asn1_utf8_string_from_der_ex(int tag, const char **a, size_t *alen, const ui
 
 static int asn1_char_is_printable(int a)
 {
-	if (isalpha(a) || isdigit(a)) {
+	if (('0' <= a && a <= '9')
+		|| ('a' <= a && a <= 'z')
+		|| ('A' <= a && a <= 'Z')) {
 		return 1;
 	}
+
 	switch (a) {
 	case ' ': case '\'': case '(': case ')':
 	case '+': case ',': case '-': case '.':
@@ -1494,7 +1497,7 @@ int asn1_time_from_str(int utc_time, time_t *timestamp, const char *str)
 
 	utc_time &= 1;
 	for (i = 0; i < time_str_len[utc_time] - 1; i++) {
-		if (!isdigit(str[i])) {
+		if (!('0' <= str[i] && str[i] <= '9')) {
 			error_print();
 			return -1;
 		}