diff --git a/src/asn1.c b/src/asn1.c
index b5bf0a86..2fee6592 100644
--- a/src/asn1.c
+++ b/src/asn1.c
@@ -302,8 +302,6 @@ int asn1_type_to_der(int tag, const uint8_t *d, size_t dlen, uint8_t **out, size
 
 int asn1_type_from_der(int tag, const uint8_t **d, size_t *dlen, const uint8_t **in, size_t *inlen)
 {
-	int ret;
-
 	if (!d || !dlen || !in || !(*in) || !inlen) {
 		error_print();
 		return -1;
@@ -367,8 +365,6 @@ int asn1_nonempty_type_from_der(int tag, const uint8_t **d, size_t *dlen, const
 
 int asn1_any_type_from_der(int *tag, const uint8_t **d, size_t *dlen, const uint8_t **in, size_t *inlen)
 {
-	int ret;
-
 	if (!tag || !d || !dlen || !in || !(*in) || !inlen) {
 		error_print();
 		return -1;
@@ -686,7 +682,7 @@ int asn1_int_from_der_ex(int tag, int *a, const uint8_t **in, size_t *inlen)
 int asn1_bit_string_to_der_ex(int tag, const uint8_t *bits, size_t nbits, uint8_t **out, size_t *outlen)
 {
 	size_t nbytes = (nbits + 7) / 8;
-	uint8_t unused_nbits = nbytes * 8 - nbits;
+	size_t unused_nbits = nbytes * 8 - nbits;
 
 	if (!outlen) {
 		error_print();
@@ -712,7 +708,7 @@ int asn1_bit_string_to_der_ex(int tag, const uint8_t *bits, size_t nbits, uint8_
 
 	// unused num of bits
 	if (out && *out) {
-		*(*out)++ = unused_nbits;
+		*(*out)++ = (uint8_t)unused_nbits;
 	}
 	(*outlen)++;
 
@@ -728,7 +724,6 @@ int asn1_bit_string_to_der_ex(int tag, const uint8_t *bits, size_t nbits, uint8_
 
 int asn1_bit_string_from_der_ex(int tag, const uint8_t **bits, size_t *nbits, const uint8_t **in, size_t *inlen)
 {
-	int ret;
 	size_t len;
 	int unused_bits;
 
@@ -1095,9 +1090,7 @@ int asn1_object_identifier_to_der_ex(int tag, const uint32_t *nodes, size_t node
 int asn1_object_identifier_from_der_ex(int tag, uint32_t *nodes, size_t *nodes_cnt,
 	const uint8_t **in, size_t *inlen)
 {
-	int ret;
 	size_t len;
-	const uint8_t *p;
 
 	// unlike _from_octets(), _from_der() require output buffer
 	if (!nodes || !nodes_cnt || !in || !(*in) || !inlen) {
diff --git a/src/sm2_lib.c b/src/sm2_lib.c
index d98260b5..f5fcb14c 100644
--- a/src/sm2_lib.c
+++ b/src/sm2_lib.c
@@ -220,7 +220,6 @@ int sm2_signature_print(FILE *fp, int fmt, int ind, const char *label, const uin
 int sm2_sign(const SM2_KEY *key, const uint8_t dgst[32], uint8_t *sigbuf, size_t *siglen)
 {
 	SM2_SIGNATURE sig;
-	uint8_t *p;
 
 	if (!key || !dgst || !sigbuf || !siglen) {
 		error_print();
@@ -276,7 +275,6 @@ int sm2_verify(const SM2_KEY *key, const uint8_t dgst[32], const uint8_t *sigbuf
 {
 	int ret;
 	SM2_SIGNATURE sig;
-	const uint8_t *p;
 
 	if (!key || !dgst || !sigbuf || !siglen) {
 		error_print();
@@ -481,7 +479,6 @@ int sm2_do_encrypt(const SM2_KEY *key, const uint8_t *in, size_t inlen, SM2_CIPH
 	SM2_JACOBIAN_POINT _kP, *kP = &_kP;
 	uint8_t x2y2[64];
 	SM3_CTX sm3_ctx;
-	size_t i;
 
 	if (!(SM2_MIN_PLAINTEXT_SIZE <= inlen && inlen <= SM2_MAX_PLAINTEXT_SIZE)) {
 		error_print();
@@ -545,7 +542,6 @@ int sm2_do_encrypt_fixlen(const SM2_KEY *key, const uint8_t *in, size_t inlen, i
 	SM2_JACOBIAN_POINT _kP, *kP = &_kP;
 	uint8_t x2y2[64];
 	SM3_CTX sm3_ctx;
-	size_t i;
 
 	if (!(SM2_MIN_PLAINTEXT_SIZE <= inlen && inlen <= SM2_MAX_PLAINTEXT_SIZE)) {
 		error_print();