diff --git a/src/debug.c b/src/debug.c
index d9d36c858..340c98ebe 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -59,7 +59,7 @@ int format_print(FILE *fp, int format, int indent, const char *str, ...)
 
 int format_bytes(FILE *fp, int format, int indent, const char *str, const uint8_t *data, size_t datalen)
 {
-	int i;
+	size_t i;
 
 	if (datalen > (1<<24)) {
 		error_print();
diff --git a/src/sm2_enc.c b/src/sm2_enc.c
index 3c4c2ea17..af7424dfa 100644
--- a/src/sm2_enc.c
+++ b/src/sm2_enc.c
@@ -142,6 +142,11 @@ int sm2_do_encrypt_ex(const SM2_KEY *key, const SM2_ENC_PRE_COMP *pre_comp,
 	uint8_t x2y2[64];
 	SM3_CTX sm3_ctx;
 
+	if (inlen < 1 || inlen > SM2_MAX_PLAINTEXT_SIZE) {
+		error_print();
+		return -1;
+	}
+
 	// output C1
 	out->point = pre_comp->C1;
 
@@ -159,7 +164,7 @@ int sm2_do_encrypt_ex(const SM2_KEY *key, const SM2_ENC_PRE_COMP *pre_comp,
 
 	// output C2 = M xor t
 	gmssl_memxor(out->ciphertext, out->ciphertext, in, inlen);
-	out->ciphertext_size = (uint32_t)inlen;
+	out->ciphertext_size = (uint8_t)inlen;
 
 	// output C3 = Hash(x2 || m || y2)
 	sm3_init(&sm3_ctx);
@@ -182,7 +187,7 @@ int sm2_do_encrypt(const SM2_KEY *key, const uint8_t *in, size_t inlen, SM2_CIPH
 	uint8_t x2y2[64];
 	SM3_CTX sm3_ctx;
 
-	if (!(SM2_MIN_PLAINTEXT_SIZE <= inlen && inlen <= SM2_MAX_PLAINTEXT_SIZE)) {
+	if (inlen < 1 || inlen > SM2_MAX_PLAINTEXT_SIZE) {
 		error_print();
 		return -1;
 	}
@@ -214,7 +219,7 @@ int sm2_do_encrypt(const SM2_KEY *key, const uint8_t *in, size_t inlen, SM2_CIPH
 
 	// output C2 = M xor t
 	gmssl_memxor(out->ciphertext, out->ciphertext, in, inlen);
-	out->ciphertext_size = (uint32_t)inlen;
+	out->ciphertext_size = (uint8_t)inlen;
 
 	// output C3 = Hash(x2 || m || y2)
 	sm3_init(&sm3_ctx);
@@ -238,7 +243,7 @@ int sm2_do_encrypt_fixlen(const SM2_KEY *key, const uint8_t *in, size_t inlen, i
 	uint8_t x2y2[64];
 	SM3_CTX sm3_ctx;
 
-	if (!(SM2_MIN_PLAINTEXT_SIZE <= inlen && inlen <= SM2_MAX_PLAINTEXT_SIZE)) {
+	if (inlen < 1 || inlen > SM2_MAX_PLAINTEXT_SIZE) {
 		error_print();
 		return -1;
 	}
@@ -295,7 +300,7 @@ int sm2_do_encrypt_fixlen(const SM2_KEY *key, const uint8_t *in, size_t inlen, i
 
 	// output C2 = M xor t
 	gmssl_memxor(out->ciphertext, out->ciphertext, in, inlen);
-	out->ciphertext_size = (uint32_t)inlen;
+	out->ciphertext_size = (uint8_t)inlen;
 
 	// output C3 = Hash(x2 || m || y2)
 	sm3_init(&sm3_ctx);
diff --git a/src/sm2_sign.c b/src/sm2_sign.c
index 312b7bedb..4a193411d 100644
--- a/src/sm2_sign.c
+++ b/src/sm2_sign.c
@@ -178,7 +178,6 @@ int sm2_fast_sign_pre_compute(SM2_SIGN_PRE_COMP pre_comp[32])
 int sm2_fast_sign(const sm2_z256_t fast_private, SM2_SIGN_PRE_COMP *pre_comp,
 	const uint8_t dgst[32], SM2_SIGNATURE *sig)
 {
-	SM2_Z256_POINT R;
 	sm2_z256_t e;
 	sm2_z256_t r;
 	sm2_z256_t s;
@@ -504,8 +503,6 @@ int sm2_compute_z(uint8_t z[32], const SM2_Z256_POINT *pub, const char *id, size
 
 int sm2_sign_init(SM2_SIGN_CTX *ctx, const SM2_KEY *key, const char *id, size_t idlen)
 {
-	size_t i;
-
 	if (!ctx || !key) {
 		error_print();
 		return -1;
diff --git a/src/sm4_ccm.c b/src/sm4_ccm.c
index 4dc69185a..faf046b91 100644
--- a/src/sm4_ccm.c
+++ b/src/sm4_ccm.c
@@ -74,7 +74,7 @@ int sm4_ccm_encrypt(const SM4_KEY *sm4_key, const uint8_t *iv, size_t ivlen,
 	}
 
 	inlen_size = 15 - ivlen;
-	if (inlen_size < 8 && inlen >= (1 << (inlen_size * 8))) {
+	if (inlen_size < 8 && inlen >= ((size_t)1 << (inlen_size * 8))) {
 		error_print();
 		return -1;
 	}
diff --git a/src/sm4_xts.c b/src/sm4_xts.c
index 12e805b19..81417e711 100644
--- a/src/sm4_xts.c
+++ b/src/sm4_xts.c
@@ -165,10 +165,7 @@ int sm4_xts_encrypt_update(SM4_XTS_CTX *ctx,
 	const uint8_t *in, size_t inlen, uint8_t *out, size_t *outlen)
 {
 	size_t DATA_UNIT_SIZE = ctx->data_unit_size;
-
 	size_t left;
-	size_t nblocks;
-	size_t len;
 
 	if (ctx->block_nbytes >= DATA_UNIT_SIZE) {
 		error_print();
@@ -253,10 +250,7 @@ int sm4_xts_decrypt_update(SM4_XTS_CTX *ctx,
 	const uint8_t *in, size_t inlen, uint8_t *out, size_t *outlen)
 {
 	size_t DATA_UNIT_SIZE = ctx->data_unit_size;
-
 	size_t left;
-	size_t nblocks;
-	size_t len;
 
 	if (ctx->block_nbytes >= DATA_UNIT_SIZE) {
 		error_print();
diff --git a/src/x509_crl.c b/src/x509_crl.c
index 776dca870..8c6ab3008 100644
--- a/src/x509_crl.c
+++ b/src/x509_crl.c
@@ -42,7 +42,7 @@ static const size_t x509_crl_reason_names_count =
 
 const char *x509_crl_reason_name(int reason)
 {
-	if (reason < 0 || reason >= x509_crl_reason_names_count) {
+	if (reason < 0 || reason >= (int)x509_crl_reason_names_count) {
 		error_print();
 		return NULL;
 	}
@@ -51,7 +51,7 @@ const char *x509_crl_reason_name(int reason)
 
 int x509_crl_reason_from_name(int *reason, const char *name)
 {
-	int i;
+	size_t i;
 	for (i = 0; i < x509_crl_reason_names_count; i++) {
 		if (strcmp(name, x509_crl_reason_names[i]) == 0) {
 			*reason = i;
diff --git a/src/x509_ext.c b/src/x509_ext.c
index 15191237d..4c8592c51 100644
--- a/src/x509_ext.c
+++ b/src/x509_ext.c
@@ -1216,7 +1216,7 @@ static size_t x509_key_usages_count =
 
 const char *x509_key_usage_name(int flag)
 {
-	int i;
+	size_t i;
 	for (i = 0; i < x509_key_usages_count; i++) {
 		if (flag & 1) {
 			if (flag >> 1) {
@@ -1233,7 +1233,7 @@ const char *x509_key_usage_name(int flag)
 
 int x509_key_usage_from_name(int *flag, const char *name)
 {
-	int i;
+	size_t i;
 	for (i = 0; i < x509_key_usages_count; i++) {
 		if (strcmp(name, x509_key_usages[i]) == 0) {
 			*flag = 1 << i;
@@ -2527,7 +2527,7 @@ static size_t x509_revoke_reason_flags_count =
 
 const char *x509_revoke_reason_flag_name(int flag)
 {
-	int i;
+	size_t i;
 	for (i = 0; i < x509_revoke_reason_flags_count; i++) {
 		if (flag & 1) {
 			if (flag >> 1) {
@@ -2543,7 +2543,7 @@ const char *x509_revoke_reason_flag_name(int flag)
 
 int x509_revoke_reason_flag_from_name(int *flag, const char *name)
 {
-	int i;
+	size_t i;
 	for (i = 0; i < x509_revoke_reason_flags_count; i++) {
 		if (strcmp(name, x509_revoke_reason_flags[i]) == 0) {
 			*flag = 1 << i;
diff --git a/tests/sm2_enctest.c b/tests/sm2_enctest.c
index d575b5361..751c04a37 100644
--- a/tests/sm2_enctest.c
+++ b/tests/sm2_enctest.c
@@ -49,7 +49,7 @@ static int test_sm2_ciphertext(void)
 		}
 
 		sm2_z256_point_to_bytes(&sm2_key.public_key, (uint8_t *)&(C.point));
-		C.ciphertext_size = tests[i].ciphertext_size;
+		C.ciphertext_size = (uint8_t)tests[i].ciphertext_size;
 
 		if (sm2_ciphertext_to_der(&C, &p, &len) != 1) {
 			error_print();
@@ -176,7 +176,6 @@ static int test_sm2_encrypt_fixlen(void)
 	};
 
 	SM2_KEY sm2_key;
-	size_t point_size;
 	uint8_t plaintext[SM2_MAX_PLAINTEXT_SIZE];
 	uint8_t encrypted[SM2_MAX_CIPHERTEXT_SIZE];
 	uint8_t decrypted[SM2_MAX_PLAINTEXT_SIZE];
diff --git a/tests/sm4_ccmtest.c b/tests/sm4_ccmtest.c
index d7bae5f61..47d7415f9 100644
--- a/tests/sm4_ccmtest.c
+++ b/tests/sm4_ccmtest.c
@@ -103,9 +103,7 @@ static int test_sm4_ccm_test_vectors(void)
 
 	SM4_KEY sm4_key;
 	uint8_t *encrypted;
-	size_t encrypted_len;
 	uint8_t *decrypted;
-	size_t decrypted_len;
 	uint8_t mac[16];
 	size_t i;
 
diff --git a/tests/sm4_cfbtest.c b/tests/sm4_cfbtest.c
index 26980d474..acd481101 100644
--- a/tests/sm4_cfbtest.c
+++ b/tests/sm4_cfbtest.c
@@ -107,9 +107,7 @@ static int test_sm4_cfb_test_vectors(void)
 
 	SM4_KEY sm4_key;
 	uint8_t *encrypted;
-	size_t encrypted_len;
 	uint8_t *decrypted;
-	size_t decrypted_len;
 	size_t i;
 
 	for (i = 0; i < sizeof(tests)/sizeof(tests[0]); i++) {
diff --git a/tests/sm4_ofbtest.c b/tests/sm4_ofbtest.c
index 2d673ec69..4e1e54171 100644
--- a/tests/sm4_ofbtest.c
+++ b/tests/sm4_ofbtest.c
@@ -98,9 +98,7 @@ static int test_sm4_ofb_test_vectors(void)
 
 	SM4_KEY sm4_key;
 	uint8_t *encrypted;
-	size_t encrypted_len;
 	uint8_t *decrypted;
-	size_t decrypted_len;
 	size_t i;
 
 	for (i = 0; i < sizeof(tests)/sizeof(tests[0]); i++) {
diff --git a/tests/sm4_xtstest.c b/tests/sm4_xtstest.c
index 4fe8b88b0..6689f9048 100644
--- a/tests/sm4_xtstest.c
+++ b/tests/sm4_xtstest.c
@@ -93,19 +93,13 @@ static int test_sm4_xts_test_vectors(void)
 	size_t key_len;
 	uint8_t iv[16];
 	size_t iv_len;
-	uint8_t *aad;
-	size_t aad_len;
-	uint8_t tag[16];
-	size_t tag_len;
 	uint8_t *plaintext;
 	size_t plaintext_len;
 	uint8_t *ciphertext;
 	size_t ciphertext_len;
 
 	uint8_t *encrypted;
-	size_t encrypted_len;
 	uint8_t *decrypted;
-	size_t decrypted_len;
 	size_t i;
 
 	for (i = 0; i < sizeof(tests)/sizeof(tests[0]); i++) {
diff --git a/tests/sm9test.c b/tests/sm9test.c
index 978c25df8..4177aa62a 100644
--- a/tests/sm9test.c
+++ b/tests/sm9test.c
@@ -799,7 +799,7 @@ int test_sm9_z256_exchange()
 	SM9_Z256_TWIST_POINT de;
 	SM9_Z256_POINT RA, RB;
 	sm9_z256_t rA;
-	int i, j = 1;
+	size_t i, j = 1;
 
 	uint8_t idA[5] = {0x41, 0x6C, 0x69, 0x63, 0x65};
 	uint8_t idB[3] = {0x42, 0x6F, 0x62};
diff --git a/tools/sm4_ecb.c b/tools/sm4_ecb.c
index 8fa112217..68b596b37 100755
--- a/tools/sm4_ecb.c
+++ b/tools/sm4_ecb.c
@@ -45,8 +45,6 @@ int sm4_ecb_main(int argc, char **argv)
 	char *outfile = NULL;
 	uint8_t key[16];
 	size_t keylen;
-	uint8_t iv[16];
-	size_t ivlen;
 	FILE *infp = stdin;
 	FILE *outfp = stdout;
 	SM4_ECB_CTX ctx;
@@ -182,7 +180,6 @@ int sm4_ecb_main(int argc, char **argv)
 
 end:
 	gmssl_secure_clear(key, sizeof(key));
-	gmssl_secure_clear(iv, sizeof(iv));
 	gmssl_secure_clear(&ctx, sizeof(ctx));
 	gmssl_secure_clear(buf, sizeof(buf));
 	if (infile && infp) fclose(infp);
diff --git a/tools/tls12_server.c b/tools/tls12_server.c
index 55aa45a05..b910a7843 100644
--- a/tools/tls12_server.c
+++ b/tools/tls12_server.c
@@ -40,7 +40,6 @@ int tls12_server_main(int argc , char **argv)
 	tls_socket_t conn_sock;
 	struct sockaddr_in server_addr;
 	struct sockaddr_in client_addr;
-	tls_socklen_t client_addrlen;
 
 	argc--;
 	argv++;
diff --git a/tools/tls13_server.c b/tools/tls13_server.c
index a86ac5cd2..2f4b6d85b 100644
--- a/tools/tls13_server.c
+++ b/tools/tls13_server.c
@@ -38,7 +38,6 @@ int tls13_server_main(int argc , char **argv)
 	tls_socket_t conn_sock;
 	struct sockaddr_in server_addr;
 	struct sockaddr_in client_addr;
-	tls_socklen_t client_addrlen;
 
 	argc--;
 	argv++;