diff --git a/src/HttpServer.cc b/src/HttpServer.cc
index 78292e9c..655ddf83 100644
--- a/src/HttpServer.cc
+++ b/src/HttpServer.cc
@@ -259,8 +259,8 @@ public:
   void accept_connection(int fd)
   {
     int val = 1;
-    setsockopt(fd, IPPROTO_TCP, TCP_NODELAY,
-               reinterpret_cast<char *>(&val), sizeof(val));
+    (void)setsockopt(fd, IPPROTO_TCP, TCP_NODELAY,
+                     reinterpret_cast<char *>(&val), sizeof(val));
     SSL *ssl = nullptr;
     if(ssl_ctx_) {
       ssl = ssl_session_new(fd);
@@ -1309,7 +1309,7 @@ int hd_on_frame_send_callback
     auto promised_stream = hd->get_stream(promised_stream_id);
     auto stream = hd->get_stream(frame->hd.stream_id);
 
-    if(!promised_stream) {
+    if(!stream || !promised_stream) {
       return 0;
     }
 
@@ -1550,7 +1550,9 @@ int start_listen(event_base *evbase, Sessions *sessions, const Config *config)
   hints.ai_flags |= AI_ADDRCONFIG;
 #endif // AI_ADDRCONFIG
 
-  auto listen_handler = new ListenEventHandler(sessions, config);
+  auto listen_handler_store =
+    util::make_unique<ListenEventHandler>(sessions, config);
+  auto listen_handler = listen_handler_store.get();
 
   addrinfo *res, *rp;
   r = getaddrinfo(nullptr, service, &hints, &res);
@@ -1585,6 +1587,8 @@ int start_listen(event_base *evbase, Sessions *sessions, const Config *config)
          LEV_OPT_REUSEABLE | LEV_OPT_CLOSE_ON_FREE, -1, fd);
       evconnlistener_set_error_cb(evlistener, evlistener_errorcb);
 
+      listen_handler_store.release();
+
       if(config->verbose) {
         std::cout << (rp->ai_family == AF_INET ? "IPv4" : "IPv6")
                   << ": listen on port "
diff --git a/src/deflatehd.cc b/src/deflatehd.cc
index 03a4deb0..af5842ff 100644
--- a/src/deflatehd.cc
+++ b/src/deflatehd.cc
@@ -86,12 +86,13 @@ static void output_to_json(nghttp2_hd_deflater *deflater,
   auto len = nghttp2_bufs_len(bufs);
   auto hex = std::vector<char>(len * 2);
   auto obj = json_object();
+  auto comp_ratio = inputlen == 0 ? 0.0 : (double)len / inputlen * 100;
 
   json_object_set_new(obj, "seq", json_integer(seq));
   json_object_set_new(obj, "input_length", json_integer(inputlen));
   json_object_set_new(obj, "output_length", json_integer(len));
   json_object_set_new(obj, "percentage_of_original_size",
-                      json_real((double)len / inputlen * 100));
+                      json_real(comp_ratio));
 
   auto hexp = hex.data();
   for(auto ci = bufs->head; ci; ci = ci->next) {
@@ -462,7 +463,10 @@ int main(int argc, char **argv)
   } else {
     perform();
   }
+
+  auto comp_ratio = input_sum == 0 ? 0.0 : (double)output_sum / input_sum;
+
   fprintf(stderr, "Overall: input=%zu output=%zu ratio=%.02f\n",
-          input_sum, output_sum, (double)output_sum / input_sum);
+          input_sum, output_sum, comp_ratio);
   return 0;
 }
diff --git a/src/h2load.cc b/src/h2load.cc
index a463c5f2..33d1e272 100644
--- a/src/h2load.cc
+++ b/src/h2load.cc
@@ -428,8 +428,8 @@ void eventcb(bufferevent *bev, short events, void *ptr)
     }
     int fd = bufferevent_getfd(bev);
     int val = 1;
-    setsockopt(fd, IPPROTO_TCP, TCP_NODELAY,
-               reinterpret_cast<char *>(&val), sizeof(val));
+    (void)setsockopt(fd, IPPROTO_TCP, TCP_NODELAY,
+                     reinterpret_cast<char *>(&val), sizeof(val));
     client->state = CLIENT_CONNECTED;
     client->on_connect();
     return;
diff --git a/src/h2load_http2_session.cc b/src/h2load_http2_session.cc
index 1a0db3ca..1b0e0fb8 100644
--- a/src/h2load_http2_session.cc
+++ b/src/h2load_http2_session.cc
@@ -24,6 +24,8 @@
  */
 #include "h2load_http2_session.h"
 
+#include <cassert>
+
 #include "h2load.h"
 #include "util.h"
 
@@ -111,6 +113,8 @@ int on_stream_close_callback
 
 void Http2Session::on_connect()
 {
+  int rv;
+
   nghttp2_session_callbacks callbacks = {0};
   callbacks.before_frame_send_callback = before_frame_send_callback;
   callbacks.on_frame_recv_callback = on_frame_recv_callback;
@@ -125,8 +129,11 @@ void Http2Session::on_connect()
   iv[0].value = 0;
   iv[1].settings_id = NGHTTP2_SETTINGS_INITIAL_WINDOW_SIZE;
   iv[1].value = (1 << client_->worker->config->window_bits) - 1;
-  nghttp2_submit_settings(session_, NGHTTP2_FLAG_NONE, iv,
-                          sizeof(iv) / sizeof(iv[0]));
+
+  rv = nghttp2_submit_settings(session_, NGHTTP2_FLAG_NONE, iv,
+                               sizeof(iv) / sizeof(iv[0]));
+
+  assert(rv == 0);
 
   auto extra_connection_window =
     (1 << client_->worker->config->connection_window_bits) - 1
diff --git a/src/shrpx.cc b/src/shrpx.cc
index 4fb00956..26ec33fe 100644
--- a/src/shrpx.cc
+++ b/src/shrpx.cc
@@ -818,7 +818,7 @@ int main(int argc, char **argv)
 
   std::vector<std::pair<const char*, const char*> > cmdcfgs;
   while(1) {
-    int flag;
+    int flag = 0;
     static option long_options[] = {
       {"daemon", no_argument, nullptr, 'D'},
       {"log-level", required_argument, nullptr, 'L'},