diff --git a/src/idempotency/client/client_channel.c b/src/idempotency/client/client_channel.c
index f2a3109..118c937 100644
--- a/src/idempotency/client/client_channel.c
+++ b/src/idempotency/client/client_channel.c
@@ -174,6 +174,7 @@ static struct fast_task_info *alloc_channel_task(IdempotencyClientChannel
         *channel, const uint32_t hash_code, const FCCommunicationType comm_type,
         const char *server_ip, const uint16_t port, int *err_no)
 {
+    int len;
     struct fast_task_info *task;
     SFAddressFamilyHandler *fh;
     SFNetworkHandler *handler;
@@ -194,7 +195,12 @@ static struct fast_task_info *alloc_channel_task(IdempotencyClientChannel
         return NULL;
     }
 
-    snprintf(task->server_ip, sizeof(task->server_ip), "%s", server_ip);
+    len = strlen(server_ip);
+    if (len >= sizeof(task->server_ip)) {
+        len = sizeof(task->server_ip) - 1;
+    }
+    memcpy(task->server_ip, server_ip, len);
+    *(task->server_ip + len) = '\0';
     task->port = port;
     task->arg = channel;
     task->thread_data = g_sf_context.thread_data +
@@ -255,7 +261,10 @@ struct idempotency_client_channel *idempotency_client_channel_get(
     IdempotencyClientChannel *current;
     IdempotencyClientChannel *channel;
 
-    key_len = snprintf(key, sizeof(key), "%s-%u", server_ip, server_port);
+    key_len = strlen(server_ip);
+    memcpy(key, server_ip, key_len);
+    *(key + key_len++) = '-';
+    key_len += fc_itoa(server_port, key + key_len);
     hash_code = fc_simple_hash(key, key_len);
     bucket = channel_context.htable.buckets +
         hash_code % channel_context.htable.capacity;
diff --git a/src/sf_binlog_index.c b/src/sf_binlog_index.c
index 62c25c5..37b9942 100644
--- a/src/sf_binlog_index.c
+++ b/src/sf_binlog_index.c
@@ -186,9 +186,11 @@ static int save(SFBinlogIndexContext *ctx, const char *filename)
     result = 0;
     p = buff;
     bend = buff + sizeof(buff);
-    p += sprintf(p, "%d %"PRId64"\n",
-            ctx->index_array.count,
-            ctx->last_version);
+
+    p += fc_itoa(ctx->index_array.count, p);
+    *p++ = ' ';
+    p += fc_itoa(ctx->last_version, p);
+    *p++ = '\n';
 
     index = ctx->index_array.indexes;
     for (i=0; i<ctx->index_array.count; i++) {
diff --git a/src/sf_global.c b/src/sf_global.c
index c4ca912..03cb242 100644
--- a/src/sf_global.c
+++ b/src/sf_global.c
@@ -865,8 +865,7 @@ static void combine_bind_addr(char *bind_addr, const char *ip_addr)
         p = bind_addr + strlen(bind_addr);
         *p++ = ',';
     }
-
-    sprintf(p, "%s", ip_addr);
+    strcpy(p, ip_addr);
 }
 
 static const char *get_address_family_caption(