diff --git a/examples/client.c b/examples/client.c
index b8fc7217..73b3ee57 100644
--- a/examples/client.c
+++ b/examples/client.c
@@ -148,11 +148,11 @@ static ssize_t send_callback(nghttp2_session *session,
                              void *user_data)
 {
   struct Connection *connection;
-  ssize_t rv;
+  int rv;
   connection = (struct Connection*)user_data;
   connection->want_io = IO_NONE;
   ERR_clear_error();
-  rv = SSL_write(connection->ssl, data, length);
+  rv = SSL_write(connection->ssl, data, (int)length);
   if(rv < 0) {
     int err = SSL_get_error(connection->ssl, rv);
     if(err == SSL_ERROR_WANT_WRITE || err == SSL_ERROR_WANT_READ) {
@@ -177,11 +177,11 @@ static ssize_t recv_callback(nghttp2_session *session,
                              void *user_data)
 {
   struct Connection *connection;
-  ssize_t rv;
+  int rv;
   connection = (struct Connection*)user_data;
   connection->want_io = IO_NONE;
   ERR_clear_error();
-  rv = SSL_read(connection->ssl, buf, length);
+  rv = SSL_read(connection->ssl, buf, (int)length);
   if(rv < 0) {
     int err = SSL_get_error(connection->ssl, rv);
     if(err == SSL_ERROR_WANT_WRITE || err == SSL_ERROR_WANT_READ) {
diff --git a/examples/libevent-client.c b/examples/libevent-client.c
index e423bd6e..a1994494 100644
--- a/examples/libevent-client.c
+++ b/examples/libevent-client.c
@@ -414,17 +414,18 @@ static int session_send(http2_session_data *session_data)
 static void readcb(struct bufferevent *bev, void *ptr)
 {
   http2_session_data *session_data = (http2_session_data*)ptr;
-  int rv;
+  ssize_t readlen;
   struct evbuffer *input = bufferevent_get_input(bev);
   size_t datalen = evbuffer_get_length(input);
   unsigned char *data = evbuffer_pullup(input, -1);
-  rv = nghttp2_session_mem_recv(session_data->session, data, datalen);
-  if(rv < 0) {
-    warnx("Fatal error: %s", nghttp2_strerror(rv));
+
+  readlen = nghttp2_session_mem_recv(session_data->session, data, datalen);
+  if(readlen < 0) {
+    warnx("Fatal error: %s", nghttp2_strerror((int)readlen));
     delete_http2_session_data(session_data);
     return;
   }
-  evbuffer_drain(input, rv);
+  evbuffer_drain(input, readlen);
   if(session_send(session_data) != 0) {
     delete_http2_session_data(session_data);
     return;
diff --git a/examples/libevent-server.c b/examples/libevent-server.c
index 239292db..fce3c409 100644
--- a/examples/libevent-server.c
+++ b/examples/libevent-server.c
@@ -83,7 +83,7 @@ static int next_proto_cb(SSL *s, const unsigned char **data, unsigned int *len,
                          void *arg)
 {
   *data = next_proto_list;
-  *len = next_proto_list_len;
+  *len = (unsigned int)next_proto_list_len;
   return SSL_TLSEXT_ERR_OK;
 }
 
@@ -240,16 +240,17 @@ static int session_send(http2_session_data *session_data)
    function. */
 static int session_recv(http2_session_data *session_data)
 {
-  int rv;
+  ssize_t readlen;
   struct evbuffer *input = bufferevent_get_input(session_data->bev);
   size_t datalen = evbuffer_get_length(input);
   unsigned char *data = evbuffer_pullup(input, -1);
-  rv = nghttp2_session_mem_recv(session_data->session, data, datalen);
-  if(rv < 0) {
-    warnx("Fatal error: %s", nghttp2_strerror(rv));
+
+  readlen = nghttp2_session_mem_recv(session_data->session, data, datalen);
+  if(readlen < 0) {
+    warnx("Fatal error: %s", nghttp2_strerror((int)readlen));
     return -1;
   }
-  evbuffer_drain(input, rv);
+  evbuffer_drain(input, readlen);
   if(session_send(session_data) != 0) {
     return -1;
   }
@@ -366,6 +367,7 @@ static int error_reply(nghttp2_session *session,
                        http2_stream_data *stream_data)
 {
   int rv;
+  ssize_t writelen;
   int pipefd[2];
   nghttp2_nv hdrs[] = {
     MAKE_NV(":status", "404")
@@ -384,10 +386,10 @@ static int error_reply(nghttp2_session *session,
     return 0;
   }
 
-  rv = write(pipefd[1], ERROR_HTML, sizeof(ERROR_HTML) - 1);
+  writelen = write(pipefd[1], ERROR_HTML, sizeof(ERROR_HTML) - 1);
   close(pipefd[1]);
 
-  if(rv != sizeof(ERROR_HTML)) {
+  if(writelen != sizeof(ERROR_HTML)) {
     close(pipefd[0]);
     return -1;
   }
diff --git a/lib/nghttp2_buf.c b/lib/nghttp2_buf.c
index 98ef493b..b0b2bd12 100644
--- a/lib/nghttp2_buf.c
+++ b/lib/nghttp2_buf.c
@@ -234,7 +234,7 @@ ssize_t nghttp2_bufs_len(nghttp2_bufs *bufs)
   return len;
 }
 
-static int bufs_avail(nghttp2_bufs *bufs)
+static ssize_t bufs_avail(nghttp2_bufs *bufs)
 {
   return nghttp2_buf_avail(&bufs->cur->buf) +
     (bufs->chunk_length - bufs->offset) * (bufs->max_chunk - bufs->chunk_used);
diff --git a/lib/nghttp2_frame.c b/lib/nghttp2_frame.c
index 105d03bd..676a9f77 100644
--- a/lib/nghttp2_frame.c
+++ b/lib/nghttp2_frame.c
@@ -359,7 +359,7 @@ int nghttp2_frame_pack_headers(nghttp2_bufs *bufs,
                                nghttp2_hd_deflater *deflater)
 {
   size_t nv_offset;
-  ssize_t rv;
+  int rv;
   nghttp2_buf *buf;
 
   assert(bufs->head == bufs->cur);
@@ -592,7 +592,7 @@ int nghttp2_frame_pack_push_promise(nghttp2_bufs *bufs,
                                     nghttp2_hd_deflater *deflater)
 {
   size_t nv_offset = 4;
-  ssize_t rv;
+  int rv;
   nghttp2_buf *buf;
 
   assert(bufs->head == bufs->cur);
@@ -970,8 +970,8 @@ void nghttp2_nv_array_sort(nghttp2_nv *nva, size_t nvlen)
   qsort(nva, nvlen, sizeof(nghttp2_nv), nv_compar);
 }
 
-ssize_t nghttp2_nv_array_copy(nghttp2_nv **nva_ptr,
-                              const nghttp2_nv *nva, size_t nvlen)
+int nghttp2_nv_array_copy(nghttp2_nv **nva_ptr,
+                          const nghttp2_nv *nva, size_t nvlen)
 {
   size_t i;
   uint8_t *data;
@@ -982,8 +982,7 @@ ssize_t nghttp2_nv_array_copy(nghttp2_nv **nva_ptr,
     buflen += nva[i].namelen + nva[i].valuelen;
   }
 
-  /* If all name/value pair is 0-length, remove them */
-  if(nvlen == 0 || buflen == 0) {
+  if(nvlen == 0) {
     *nva_ptr = NULL;
 
     return 0;
@@ -1014,7 +1013,7 @@ ssize_t nghttp2_nv_array_copy(nghttp2_nv **nva_ptr,
     data += nva[i].valuelen;
     ++p;
   }
-  return nvlen;
+  return 0;
 }
 
 int nghttp2_iv_check(const nghttp2_settings_entry *iv, size_t niv)
diff --git a/lib/nghttp2_frame.h b/lib/nghttp2_frame.h
index 662345e5..c398ceb3 100644
--- a/lib/nghttp2_frame.h
+++ b/lib/nghttp2_frame.h
@@ -589,14 +589,14 @@ void nghttp2_nv_array_sort(nghttp2_nv *nva, size_t nvlen);
  *
  * The |*nva_ptr| must be freed using nghttp2_nv_array_del().
  *
- * This function returns the number of name/value pairs in |*nva_ptr|,
- * or one of the following negative error codes:
+ * This function returns 0 if it succeeds or one of the following
+ * negative error codes:
  *
  * NGHTTP2_ERR_NOMEM
  *     Out of memory.
  */
-ssize_t nghttp2_nv_array_copy(nghttp2_nv **nva_ptr,
-                              const nghttp2_nv *nva, size_t nvlen);
+int nghttp2_nv_array_copy(nghttp2_nv **nva_ptr,
+                          const nghttp2_nv *nva, size_t nvlen);
 
 /*
  * Returns nonzero if the name/value pair |a| equals to |b|. The name
diff --git a/lib/nghttp2_hd.c b/lib/nghttp2_hd.c
index 3af4d47d..e1c4316c 100644
--- a/lib/nghttp2_hd.c
+++ b/lib/nghttp2_hd.c
@@ -443,7 +443,7 @@ static int emit_literal_header(nghttp2_nv *nv_out, nghttp2_nv *nv)
   return 0;
 }
 
-static size_t count_encoded_length(size_t n, int prefix)
+static size_t count_encoded_length(size_t n, size_t prefix)
 {
   size_t k = (1 << prefix) - 1;
   size_t len = 0;
@@ -464,7 +464,7 @@ static size_t count_encoded_length(size_t n, int prefix)
   return len;
 }
 
-static size_t encode_length(uint8_t *buf, size_t n, int prefix)
+static size_t encode_length(uint8_t *buf, size_t n, size_t prefix)
 {
   size_t k = (1 << prefix) - 1;
   size_t len = 0;
@@ -507,8 +507,8 @@ static size_t encode_length(uint8_t *buf, size_t n, int prefix)
  * partial decoding, or stores -1 in |*res|, indicating decoding
  * error.
  */
-static  uint8_t* decode_length(ssize_t *res, int *final, ssize_t initial,
-                               uint8_t *in, uint8_t *last, int prefix)
+static uint8_t* decode_length(ssize_t *res, int *final, ssize_t initial,
+                              uint8_t *in, uint8_t *last, size_t prefix)
 {
   int k = (1 << prefix) - 1, r;
   ssize_t n = initial;
@@ -624,7 +624,7 @@ static int emit_string(nghttp2_bufs *bufs,
                        size_t enclen, int huffman,
                        const uint8_t *str, size_t len)
 {
-  size_t rv;
+  int rv;
   uint8_t sb[16];
   uint8_t *bufp;
   size_t blocklen;
@@ -998,7 +998,7 @@ static int check_index_range(nghttp2_hd_context *context, size_t idx)
   return idx < context->hd_table.len + STATIC_TABLE_LENGTH;
 }
 
-static int get_max_index(nghttp2_hd_context *context)
+static size_t get_max_index(nghttp2_hd_context *context)
 {
   return context->hd_table.len + STATIC_TABLE_LENGTH - 1;
 }
@@ -1352,7 +1352,7 @@ static void hd_inflate_set_huffman_encoded(nghttp2_hd_inflater *inflater,
 static ssize_t hd_inflate_read_len(nghttp2_hd_inflater *inflater,
                                    int *rfin,
                                    uint8_t *in, uint8_t *last,
-                                   int prefix, size_t maxlen)
+                                   size_t prefix, size_t maxlen)
 {
   uint8_t *nin;
   *rfin = 0;
@@ -1389,21 +1389,21 @@ static ssize_t hd_inflate_read_huff(nghttp2_hd_inflater *inflater,
                                     nghttp2_bufs *bufs,
                                     uint8_t *in, uint8_t *last)
 {
-  int rv;
+  ssize_t readlen;
   int final = 0;
   if(last - in >= inflater->left) {
     last = in + inflater->left;
     final = 1;
   }
-  rv = nghttp2_hd_huff_decode(&inflater->huff_decode_ctx, bufs,
-                              in, last - in, final);
+  readlen = nghttp2_hd_huff_decode(&inflater->huff_decode_ctx, bufs,
+                                   in, last - in, final);
 
-  if(rv < 0) {
+  if(readlen < 0) {
     DEBUGF(fprintf(stderr, "inflatehd: huffman decoding failed\n"));
-    return rv;
+    return readlen;
   }
-  inflater->left -= rv;
-  return rv;
+  inflater->left -= readlen;
+  return readlen;
 }
 
 /*
@@ -1925,7 +1925,7 @@ ssize_t nghttp2_hd_inflate_hd(nghttp2_hd_inflater *inflater,
       rv = hd_inflate_read(inflater, &inflater->nvbufs, in, last);
       if(rv < 0) {
         DEBUGF(fprintf(stderr, "inflatehd: value read failure %zd: %s\n",
-                       rv, nghttp2_strerror(rv)));
+                       rv, nghttp2_strerror((int)rv)));
         goto fail;
       }
 
diff --git a/lib/nghttp2_hd_huffman.c b/lib/nghttp2_hd_huffman.c
index 608cc0f2..860b38d4 100644
--- a/lib/nghttp2_hd_huffman.c
+++ b/lib/nghttp2_hd_huffman.c
@@ -114,7 +114,7 @@ int nghttp2_hd_huff_encode(nghttp2_bufs *bufs,
                            const uint8_t *src, size_t srclen)
 {
   int rv;
-  int rembits = 8;
+  ssize_t rembits = 8;
   size_t i;
   size_t avail;
 
@@ -135,7 +135,7 @@ int nghttp2_hd_huff_encode(nghttp2_bufs *bufs,
     }
     rembits = huff_encode_sym(bufs, &avail, rembits, sym);
     if(rembits < 0) {
-      return rembits;
+      return (int)rembits;
     }
   }
   /* 256 is special terminal symbol, pad with its prefix */
diff --git a/lib/nghttp2_map.c b/lib/nghttp2_map.c
index 4d50413b..9197ba4f 100644
--- a/lib/nghttp2_map.c
+++ b/lib/nghttp2_map.c
@@ -88,7 +88,7 @@ void nghttp2_map_entry_init(nghttp2_map_entry *entry, key_type key)
 
 /* Same hash function in android HashMap source code. */
 /* The |mod| must be power of 2 */
-static int32_t hash(int32_t h, int32_t mod)
+static int32_t hash(int32_t h, size_t mod)
 {
   h ^= (h >> 20) ^ (h >> 12);
   h ^= (h >> 7) ^ (h >> 4);
diff --git a/lib/nghttp2_session.c b/lib/nghttp2_session.c
index f7643acf..ad7aaea8 100644
--- a/lib/nghttp2_session.c
+++ b/lib/nghttp2_session.c
@@ -1451,8 +1451,8 @@ static int session_headers_add_pad(nghttp2_session *session,
 
   padded_payloadlen = session_call_select_padding(session, frame,
                                                   NGHTTP2_MAX_PAYLOADLEN);
-  if(nghttp2_is_fatal(padded_payloadlen)) {
-    return padded_payloadlen;
+  if(nghttp2_is_fatal((int)padded_payloadlen)) {
+    return (int)padded_payloadlen;
   }
 
   padlen = padded_payloadlen - frame->hd.length;
@@ -1546,7 +1546,7 @@ static int session_consider_blocked(nghttp2_session *session,
 static int session_prep_frame(nghttp2_session *session,
                               nghttp2_outbound_item *item)
 {
-  ssize_t framerv = 0;
+  int framerv = 0;
   int rv;
 
   if(item->frame_cat == NGHTTP2_CAT_CTRL) {
@@ -2464,7 +2464,7 @@ int nghttp2_session_send(nghttp2_session *session)
   for(;;) {
     datalen = nghttp2_session_mem_send(session, &data);
     if(datalen <= 0) {
-      return datalen;
+      return (int)datalen;
     }
     sentlen = session->callbacks.send_callback(session, data, datalen, 0,
                                                session->user_data);
@@ -2655,13 +2655,14 @@ static int session_inflate_handle_invalid_connection
  * NGHTTP2_ERR_HEADER_COMP
  *     Header decompression failed
  */
-static ssize_t inflate_header_block(nghttp2_session *session,
-                                    nghttp2_frame *frame,
-                                    size_t *readlen_ptr,
-                                    uint8_t *in, size_t inlen,
-                                    int final, int call_header_cb)
+static int inflate_header_block(nghttp2_session *session,
+                                nghttp2_frame *frame,
+                                size_t *readlen_ptr,
+                                uint8_t *in, size_t inlen,
+                                int final, int call_header_cb)
 {
-  ssize_t rv;
+  ssize_t proclen;
+  int rv;
   int inflate_flags;
   nghttp2_nv nv;
   nghttp2_stream *stream;
@@ -2671,12 +2672,12 @@ static ssize_t inflate_header_block(nghttp2_session *session,
   DEBUGF(fprintf(stderr, "recv: decoding header block %zu bytes\n", inlen));
   for(;;) {
     inflate_flags = 0;
-    rv = nghttp2_hd_inflate_hd(&session->hd_inflater, &nv, &inflate_flags,
-                               in, inlen, final);
-    if(nghttp2_is_fatal(rv)) {
-      return rv;
+    proclen = nghttp2_hd_inflate_hd(&session->hd_inflater, &nv, &inflate_flags,
+                                    in, inlen, final);
+    if(nghttp2_is_fatal((int)proclen)) {
+      return (int)proclen;
     }
-    if(rv < 0) {
+    if(proclen < 0) {
       if(session->iframe.state == NGHTTP2_IB_READ_HEADER_BLOCK) {
         stream = nghttp2_session_get_stream(session, frame->hd.stream_id);
 
@@ -2700,9 +2701,9 @@ static ssize_t inflate_header_block(nghttp2_session *session,
 
       return NGHTTP2_ERR_HEADER_COMP;
     }
-    in += rv;
-    inlen -= rv;
-    *readlen_ptr += rv;
+    in += proclen;
+    inlen -= proclen;
+    *readlen_ptr += proclen;
     if(call_header_cb && (inflate_flags & NGHTTP2_HD_INFLATE_EMIT)) {
       rv = session_call_on_header(session, frame, &nv);
       /* This handles NGHTTP2_ERR_PAUSE and
@@ -3923,11 +3924,11 @@ static int session_process_data_frame(nghttp2_session *session)
  * return -1 too.
  */
 static int adjust_recv_window_size(int32_t *recv_window_size_ptr,
-                                   int32_t delta,
+                                   size_t delta,
                                    int32_t local_window_size)
 {
-  if(*recv_window_size_ptr > local_window_size - delta ||
-     *recv_window_size_ptr > NGHTTP2_MAX_WINDOW_SIZE - delta) {
+  if(*recv_window_size_ptr > local_window_size - (int32_t)delta ||
+     *recv_window_size_ptr > NGHTTP2_MAX_WINDOW_SIZE - (int32_t)delta) {
     return -1;
   }
   *recv_window_size_ptr += delta;
@@ -3949,7 +3950,7 @@ static int adjust_recv_window_size(int32_t *recv_window_size_ptr,
 static int session_update_recv_stream_window_size
 (nghttp2_session *session,
  nghttp2_stream *stream,
- int32_t delta_size,
+ size_t delta_size,
  int send_window_update)
 {
   int rv;
@@ -3995,7 +3996,7 @@ static int session_update_recv_stream_window_size
  */
 static int session_update_recv_connection_window_size
 (nghttp2_session *session,
- int32_t delta_size)
+ size_t delta_size)
 {
   int rv;
   rv = adjust_recv_window_size(&session->recv_window_size, delta_size,
@@ -4228,6 +4229,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session,
   const uint8_t *first = in, *last = in + inlen;
   nghttp2_inbound_frame *iframe = &session->iframe;
   size_t readlen;
+  ssize_t padlen;
   int rv;
   int busy = 0;
   nghttp2_frame_hd cont_hd;
@@ -4596,8 +4598,8 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session,
       case NGHTTP2_HEADERS:
         if(iframe->padlen == 0 &&
            iframe->frame.hd.flags & NGHTTP2_FLAG_PADDED) {
-          rv = inbound_frame_compute_pad(iframe);
-          if(rv < 0) {
+          padlen = inbound_frame_compute_pad(iframe);
+          if(padlen < 0) {
             busy = 1;
             rv = nghttp2_session_terminate_session(session,
                                                    NGHTTP2_PROTOCOL_ERROR);
@@ -4607,7 +4609,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session,
             iframe->state = NGHTTP2_IB_IGN_PAYLOAD;
             break;
           }
-          iframe->frame.headers.padlen = rv;
+          iframe->frame.headers.padlen = padlen;
 
           pri_fieldlen = nghttp2_frame_priority_len(iframe->frame.hd.flags);
 
@@ -4662,8 +4664,8 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session,
       case NGHTTP2_PUSH_PROMISE:
         if(iframe->padlen == 0 &&
            iframe->frame.hd.flags & NGHTTP2_FLAG_PADDED) {
-          rv = inbound_frame_compute_pad(iframe);
-          if(rv < 0) {
+          padlen = inbound_frame_compute_pad(iframe);
+          if(padlen < 0) {
             busy = 1;
             rv = nghttp2_session_terminate_session(session,
                                                    NGHTTP2_PROTOCOL_ERROR);
@@ -4674,7 +4676,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session,
             break;
           }
 
-          iframe->frame.push_promise.padlen = rv;
+          iframe->frame.push_promise.padlen = padlen;
 
           if(iframe->payloadleft < 4) {
             busy = 1;
@@ -5081,8 +5083,8 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session,
 
       busy = 1;
 
-      rv = inbound_frame_compute_pad(iframe);
-      if(rv < 0) {
+      padlen = inbound_frame_compute_pad(iframe);
+      if(padlen < 0) {
         rv = nghttp2_session_terminate_session(session,
                                                NGHTTP2_PROTOCOL_ERROR);
         if(nghttp2_is_fatal(rv)) {
@@ -5092,7 +5094,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session,
         break;
       }
 
-      iframe->frame.data.padlen = rv;
+      iframe->frame.data.padlen = padlen;
 
       iframe->state = NGHTTP2_IB_READ_DATA;
 
@@ -5212,13 +5214,13 @@ int nghttp2_session_recv(nghttp2_session *session)
     if(readlen > 0) {
       ssize_t proclen = nghttp2_session_mem_recv(session, buf, readlen);
       if(proclen < 0) {
-        return proclen;
+        return (int)proclen;
       }
       assert(proclen == readlen);
     } else if(readlen == 0 || readlen == NGHTTP2_ERR_WOULDBLOCK) {
       return 0;
     } else if(readlen == NGHTTP2_ERR_EOF) {
-      return readlen;
+      return NGHTTP2_ERR_EOF;
     } else if(readlen < 0) {
       return NGHTTP2_ERR_CALLBACK_FAILURE;
     }
@@ -5439,7 +5441,7 @@ int nghttp2_session_pack_data(nghttp2_session *session,
                               size_t datamax,
                               nghttp2_private_data *frame)
 {
-  ssize_t rv;
+  int rv;
   uint32_t data_flags;
   uint8_t flags;
   ssize_t payloadlen;
@@ -5464,9 +5466,9 @@ int nghttp2_session_pack_data(nghttp2_session *session,
   if(payloadlen == NGHTTP2_ERR_DEFERRED ||
      payloadlen == NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE) {
     DEBUGF(fprintf(stderr, "send: DATA postponed due to %s\n",
-                   nghttp2_strerror(payloadlen)));
+                   nghttp2_strerror((int)payloadlen)));
 
-    return payloadlen;
+    return (int)payloadlen;
   }
 
   if(payloadlen < 0 || datamax < (size_t)payloadlen) {
@@ -5501,8 +5503,8 @@ int nghttp2_session_pack_data(nghttp2_session *session,
 
   padded_payloadlen = session_call_select_padding(session, &data_frame,
                                                   datamax);
-  if(nghttp2_is_fatal(padded_payloadlen)) {
-    return padded_payloadlen;
+  if(nghttp2_is_fatal((int)padded_payloadlen)) {
+    return (int)padded_payloadlen;
   }
 
   padlen = padded_payloadlen - payloadlen;
@@ -5620,7 +5622,7 @@ int32_t nghttp2_session_get_stream_remote_window_size(nghttp2_session* session,
     return -1;
   }
 
-  return nghttp2_session_next_data_read(session, stream);
+  return (int32_t)nghttp2_session_next_data_read(session, stream);
 }
 
 uint32_t nghttp2_session_get_remote_settings(nghttp2_session *session,
diff --git a/lib/nghttp2_stream.c b/lib/nghttp2_stream.c
index 0ac29e7e..00bf6216 100644
--- a/lib/nghttp2_stream.c
+++ b/lib/nghttp2_stream.c
@@ -420,7 +420,7 @@ static int update_initial_window_size
      new_window_size > NGHTTP2_MAX_WINDOW_SIZE) {
     return -1;
   }
-  *window_size_ptr = new_window_size;
+  *window_size_ptr = (int32_t)new_window_size;
   return 0;
 }
 
diff --git a/lib/nghttp2_submit.c b/lib/nghttp2_submit.c
index 310addb8..bc43b5b9 100644
--- a/lib/nghttp2_submit.c
+++ b/lib/nghttp2_submit.c
@@ -148,7 +148,7 @@ static int32_t submit_headers_shared_nva
  const nghttp2_data_provider *data_prd,
  void *stream_user_data)
 {
-  ssize_t rv;
+  int rv;
   nghttp2_nv *nva_copy;
   nghttp2_priority_spec copy_pri_spec;
 
@@ -165,7 +165,7 @@ static int32_t submit_headers_shared_nva
   }
 
   return submit_headers_shared(session, flags, stream_id,
-                               &copy_pri_spec, nva_copy, rv, data_prd,
+                               &copy_pri_spec, nva_copy, nvlen, data_prd,
                                stream_user_data);
 }
 
diff --git a/src/nghttp2_gzip.c b/src/nghttp2_gzip.c
index d7fc13e0..1e2b8808 100644
--- a/src/nghttp2_gzip.c
+++ b/src/nghttp2_gzip.c
@@ -63,9 +63,9 @@ int nghttp2_gzip_inflate(nghttp2_gzip *inflater,
   if(inflater->finished) {
     return -1;
   }
-  inflater->zst.avail_in = *inlen_ptr;
+  inflater->zst.avail_in = (unsigned int)*inlen_ptr;
   inflater->zst.next_in = (unsigned char*)in;
-  inflater->zst.avail_out = *outlen_ptr;
+  inflater->zst.avail_out = (unsigned int)*outlen_ptr;
   inflater->zst.next_out = out;
 
   rv = inflate(&inflater->zst, Z_NO_FLUSH);
diff --git a/src/nghttp2_gzip_test.c b/src/nghttp2_gzip_test.c
index 0592d1e1..7549f460 100644
--- a/src/nghttp2_gzip_test.c
+++ b/src/nghttp2_gzip_test.c
@@ -46,9 +46,9 @@ static ssize_t deflate_data(uint8_t *out, size_t outlen,
   rv = deflateInit(&zst, Z_DEFAULT_COMPRESSION);
   assert(rv == Z_OK);
 
-  zst.avail_in = inlen;
+  zst.avail_in = (unsigned int)inlen;
   zst.next_in = (uint8_t*)in;
-  zst.avail_out = outlen;
+  zst.avail_out = (unsigned int)outlen;
   zst.next_out = out;
   rv = deflate(&zst, Z_SYNC_FLUSH);
   assert(rv == Z_OK);
diff --git a/tests/failmalloc_test.c b/tests/failmalloc_test.c
index 5e22e9fe..38e3ccdf 100644
--- a/tests/failmalloc_test.c
+++ b/tests/failmalloc_test.c
@@ -254,7 +254,8 @@ static void run_nghttp2_session_recv(void)
   ud.df = &df;
 
   nghttp2_failmalloc_pause();
-  nvlen = nghttp2_nv_array_copy(&nva, nv, ARRLEN(nv));
+  nvlen = ARRLEN(nv);
+  nghttp2_nv_array_copy(&nva, nv, nvlen);
   nghttp2_hd_deflate_init(&deflater);
   nghttp2_session_server_new(&session, &callbacks, &ud);
   nghttp2_failmalloc_unpause();
@@ -362,8 +363,9 @@ static void run_nghttp2_frame_pack_headers(void)
   if(rv != 0) {
     goto inflate_init_fail;
   }
-  nvlen = nghttp2_nv_array_copy(&nva, nv, ARRLEN(nv));
-  if(nvlen < 0) {
+  nvlen = ARRLEN(nv);
+  rv = nghttp2_nv_array_copy(&nva, nv, nvlen);
+  if(rv < 0) {
     goto nv_copy_fail;
   }
   nghttp2_frame_headers_init(&frame.headers, NGHTTP2_FLAG_END_STREAM,
diff --git a/tests/nghttp2_buf_test.c b/tests/nghttp2_buf_test.c
index a39e027f..9367645e 100644
--- a/tests/nghttp2_buf_test.c
+++ b/tests/nghttp2_buf_test.c
@@ -164,6 +164,7 @@ void test_nghttp2_bufs_remove(void)
   nghttp2_buf_chain *chain;
   int i;
   uint8_t *out;
+  ssize_t outlen;
 
   rv = nghttp2_bufs_init(&bufs, 1000, 3);
   CU_ASSERT(0 == rv);
@@ -185,10 +186,10 @@ void test_nghttp2_bufs_remove(void)
   rv = nghttp2_bufs_add(&bufs, "world", 5);
   CU_ASSERT(0 == rv);
 
-  rv = nghttp2_bufs_remove(&bufs, &out);
-  CU_ASSERT(11 == rv);
+  outlen = nghttp2_bufs_remove(&bufs, &out);
+  CU_ASSERT(11 == outlen);
 
-  CU_ASSERT(0 == memcmp("hello world", out, rv));
+  CU_ASSERT(0 == memcmp("hello world", out, outlen));
   CU_ASSERT(0 == nghttp2_bufs_len(&bufs));
   CU_ASSERT(bufs.cur->buf.pos == bufs.cur->buf.begin);
 
diff --git a/tests/nghttp2_frame_test.c b/tests/nghttp2_frame_test.c
index 99351242..5f772a34 100644
--- a/tests/nghttp2_frame_test.c
+++ b/tests/nghttp2_frame_test.c
@@ -172,7 +172,6 @@ void test_nghttp2_frame_pack_headers_frame_too_large(void)
   nghttp2_headers frame;
   nghttp2_bufs bufs;
   nghttp2_nv *nva;
-  ssize_t nvlen;
   size_t big_vallen = NGHTTP2_HD_MAX_NV;
   nghttp2_nv big_hds[16];
   size_t big_hdslen = ARRLEN(big_hds);
@@ -184,19 +183,19 @@ void test_nghttp2_frame_pack_headers_frame_too_large(void)
   for(i = 0; i < big_hdslen; ++i) {
     big_hds[i].name = (uint8_t*)"header";
     big_hds[i].value = malloc(big_vallen+1);
-    memset(big_hds[i].value, '0'+i, big_vallen);
+    memset(big_hds[i].value, '0' + (int)i, big_vallen);
     big_hds[i].value[big_vallen] = '\0';
     big_hds[i].namelen = strlen((char*)big_hds[i].name);
     big_hds[i].valuelen = big_vallen;
     big_hds[i].flags = NGHTTP2_NV_FLAG_NONE;
   }
 
-  nvlen = nghttp2_nv_array_copy(&nva, big_hds, big_hdslen);
+  nghttp2_nv_array_copy(&nva, big_hds, big_hdslen);
   nghttp2_hd_deflate_init(&deflater);
   nghttp2_frame_headers_init(&frame,
                              NGHTTP2_FLAG_END_STREAM|NGHTTP2_FLAG_END_HEADERS,
                              1000000007, NGHTTP2_HCAT_REQUEST,
-                             NULL, nva, nvlen);
+                             NULL, nva, big_hdslen);
   rv = nghttp2_frame_pack_headers(&bufs, &frame, &deflater);
   CU_ASSERT(NGHTTP2_ERR_HEADER_COMP == rv);
 
@@ -611,10 +610,15 @@ void test_nghttp2_nv_array_copy(void)
 
   rv = nghttp2_nv_array_copy(&nva, emptynv, ARRLEN(emptynv));
   CU_ASSERT(0 == rv);
-  CU_ASSERT(NULL == nva);
+  CU_ASSERT(nva[0].namelen == 0);
+  CU_ASSERT(nva[0].valuelen == 0);
+  CU_ASSERT(nva[1].namelen == 0);
+  CU_ASSERT(nva[1].valuelen == 0);
+
+  nghttp2_nv_array_del(nva);
 
   rv = nghttp2_nv_array_copy(&nva, nv, ARRLEN(nv));
-  CU_ASSERT(2 == rv);
+  CU_ASSERT(0 == rv);
   CU_ASSERT(nva[0].namelen == 5);
   CU_ASSERT(0 == memcmp("alpha", nva[0].name, 5));
   CU_ASSERT(nva[0].valuelen = 5);
@@ -628,7 +632,7 @@ void test_nghttp2_nv_array_copy(void)
 
   /* Large header field is acceptable */
   rv = nghttp2_nv_array_copy(&nva, &bignv, 1);
-  CU_ASSERT(1 == rv);
+  CU_ASSERT(0 == rv);
 
   nghttp2_nv_array_del(nva);
 
diff --git a/tests/nghttp2_pq_test.c b/tests/nghttp2_pq_test.c
index 0f9d89ba..32ee893c 100644
--- a/tests/nghttp2_pq_test.c
+++ b/tests/nghttp2_pq_test.c
@@ -104,13 +104,13 @@ void test_nghttp2_pq_update(void)
 {
   nghttp2_pq pq;
   node nodes[10];
-  size_t i;
+  int i;
   node *nd;
   int ans[] = {-8, -6, -4, -2, 0, 1, 3, 5, 7, 9};
 
   nghttp2_pq_init(&pq, node_compar);
 
-  for(i = 0; i < sizeof(nodes)/sizeof(nodes[0]); ++i) {
+  for(i = 0; i < (int)(sizeof(nodes)/sizeof(nodes[0])); ++i) {
     nodes[i].key = i;
     nodes[i].val = i;
     nghttp2_pq_push(&pq, &nodes[i]);
@@ -118,7 +118,7 @@ void test_nghttp2_pq_update(void)
 
   nghttp2_pq_update(&pq, node_update, NULL);
 
-  for(i = 0; i < sizeof(nodes)/sizeof(nodes[0]); ++i) {
+  for(i = 0; i < (int)(sizeof(nodes)/sizeof(nodes[0])); ++i) {
     nd = nghttp2_pq_top(&pq);
     CU_ASSERT(ans[i] == nd->key);
     nghttp2_pq_pop(&pq);
diff --git a/tests/nghttp2_session_test.c b/tests/nghttp2_session_test.c
index 0edbe491..2bfea0dd 100644
--- a/tests/nghttp2_session_test.c
+++ b/tests/nghttp2_session_test.c
@@ -279,7 +279,7 @@ static ssize_t block_count_send_callback(nghttp2_session* session,
                                          void *user_data)
 {
   my_user_data *ud = (my_user_data*)user_data;
-  int r;
+  ssize_t r;
   if(ud->block_count == 0) {
     r = NGHTTP2_ERR_WOULDBLOCK;
   } else {
@@ -388,7 +388,8 @@ void test_nghttp2_session_recv(void)
   nghttp2_session_server_new(&session, &callbacks, &user_data);
   nghttp2_hd_deflate_init(&deflater);
 
-  nvlen = nghttp2_nv_array_copy(&nva, nv, ARRLEN(nv));
+  nvlen = ARRLEN(nv);
+  nghttp2_nv_array_copy(&nva, nv, nvlen);
   nghttp2_frame_headers_init(&frame.headers, NGHTTP2_FLAG_END_HEADERS,
                              1, NGHTTP2_HCAT_HEADERS, NULL, nva, nvlen);
   rv = nghttp2_frame_pack_headers(&bufs, &frame.headers, &deflater);
@@ -533,7 +534,8 @@ void test_nghttp2_session_recv_invalid_frame(void)
   user_data.frame_send_cb_called = 0;
   nghttp2_session_server_new(&session, &callbacks, &user_data);
   nghttp2_hd_deflate_init(&deflater);
-  nvlen = nghttp2_nv_array_copy(&nva, nv, ARRLEN(nv));
+  nvlen = ARRLEN(nv);
+  nghttp2_nv_array_copy(&nva, nv, nvlen);
   nghttp2_frame_headers_init(&frame.headers, NGHTTP2_FLAG_END_HEADERS, 1,
                              NGHTTP2_HCAT_HEADERS, NULL, nva, nvlen);
   rv = nghttp2_frame_pack_headers(&bufs, &frame.headers, &deflater);
@@ -583,7 +585,7 @@ void test_nghttp2_session_recv_data(void)
   nghttp2_session_callbacks callbacks;
   my_user_data ud;
   uint8_t data[8092];
-  int rv;
+  ssize_t rv;
   nghttp2_outbound_item *item;
   nghttp2_stream *stream;
   nghttp2_frame_hd hd;
@@ -735,7 +737,8 @@ void test_nghttp2_session_recv_continuation(void)
   nghttp2_hd_deflate_init(&deflater);
 
   /* Make 1 HEADERS and insert CONTINUATION header */
-  nvlen = nghttp2_nv_array_copy(&nva, nv1, ARRLEN(nv1));
+  nvlen = ARRLEN(nv1);
+  nghttp2_nv_array_copy(&nva, nv1, nvlen);
   nghttp2_frame_headers_init(&frame.headers, NGHTTP2_FLAG_NONE, 1,
                              NGHTTP2_HCAT_HEADERS, NULL, nva, nvlen);
   rv = nghttp2_frame_pack_headers(&bufs, &frame.headers, &deflater);
@@ -797,7 +800,8 @@ void test_nghttp2_session_recv_continuation(void)
   nghttp2_hd_deflate_init(&deflater);
 
   /* HEADERS without END_HEADERS flag */
-  nvlen = nghttp2_nv_array_copy(&nva, nv1, ARRLEN(nv1));
+  nvlen = ARRLEN(nv1);
+  nghttp2_nv_array_copy(&nva, nv1, nvlen);
   nghttp2_frame_headers_init(&frame.headers, NGHTTP2_FLAG_NONE, 1,
                              NGHTTP2_HCAT_HEADERS, NULL, nva, nvlen);
   nghttp2_bufs_reset(&bufs);
@@ -874,7 +878,8 @@ void test_nghttp2_session_recv_headers_with_priority(void)
   open_stream(session, 1);
 
   /* With NGHTTP2_FLAG_PRIORITY without exclusive flag set */
-  nvlen = nghttp2_nv_array_copy(&nva, nv1, ARRLEN(nv1));
+  nvlen = ARRLEN(nv1);
+  nghttp2_nv_array_copy(&nva, nv1, nvlen);
 
   nghttp2_priority_spec_init(&pri_spec, 1, 99, 0);
 
@@ -908,7 +913,8 @@ void test_nghttp2_session_recv_headers_with_priority(void)
 
   /* With NGHTTP2_FLAG_PRIORITY, but cut last 1 byte to make it
      invalid. */
-  nvlen = nghttp2_nv_array_copy(&nva, nv1, ARRLEN(nv1));
+  nvlen = ARRLEN(nv1);
+  nghttp2_nv_array_copy(&nva, nv1, nvlen);
 
   nghttp2_priority_spec_init(&pri_spec, 0, 99, 0);
 
@@ -954,7 +960,8 @@ void test_nghttp2_session_recv_headers_with_priority(void)
 
   nghttp2_hd_deflate_init(&deflater);
 
-  nvlen = nghttp2_nv_array_copy(&nva, nv1, ARRLEN(nv1));
+  nvlen = ARRLEN(nv1);
+  nghttp2_nv_array_copy(&nva, nv1, nvlen);
 
   nghttp2_priority_spec_init(&pri_spec, 1, 0, 0);
 
@@ -1021,7 +1028,8 @@ void test_nghttp2_session_recv_premature_headers(void)
 
   nghttp2_hd_deflate_init(&deflater);
 
-  nvlen = nghttp2_nv_array_copy(&nva, nv1, ARRLEN(nv1));
+  nvlen = ARRLEN(nv1);
+  nghttp2_nv_array_copy(&nva, nv1, nvlen);
   nghttp2_frame_headers_init(&frame.headers, NGHTTP2_FLAG_END_HEADERS, 1,
                              NGHTTP2_HCAT_HEADERS, NULL, nva, nvlen);
   rv = nghttp2_frame_pack_headers(&bufs, &frame.headers, &deflater);
@@ -1264,7 +1272,8 @@ void test_nghttp2_session_continue(void)
   nghttp2_hd_deflate_init(&deflater);
 
   /* Make 2 HEADERS frames */
-  nvlen = nghttp2_nv_array_copy(&nva, nv1, ARRLEN(nv1));
+  nvlen = ARRLEN(nv1);
+  nghttp2_nv_array_copy(&nva, nv1, nvlen);
   nghttp2_frame_headers_init(&frame.headers, NGHTTP2_FLAG_END_HEADERS, 1,
                              NGHTTP2_HCAT_HEADERS, NULL, nva, nvlen);
   rv = nghttp2_frame_pack_headers(&bufs, &frame.headers, &deflater);
@@ -1280,7 +1289,8 @@ void test_nghttp2_session_continue(void)
   framelen1 = nghttp2_buf_len(buf);
   databuf.last = nghttp2_cpymem(databuf.last, buf->pos, nghttp2_buf_len(buf));
 
-  nvlen = nghttp2_nv_array_copy(&nva, nv2, ARRLEN(nv2));
+  nvlen = ARRLEN(nv2);
+  nghttp2_nv_array_copy(&nva, nv2, nvlen);
   nghttp2_frame_headers_init(&frame.headers, NGHTTP2_FLAG_END_HEADERS, 3,
                              NGHTTP2_HCAT_HEADERS, NULL, nva, nvlen);
   nghttp2_bufs_reset(&bufs);
@@ -1442,7 +1452,8 @@ void test_nghttp2_session_add_frame(void)
   CU_ASSERT(0 == nghttp2_session_client_new(&session, &callbacks, &user_data));
 
   frame = malloc(sizeof(nghttp2_frame));
-  nvlen = nghttp2_nv_array_copy(&nva, nv, ARRLEN(nv));
+  nvlen = ARRLEN(nv);
+  nghttp2_nv_array_copy(&nva, nv, nvlen);
 
   nghttp2_frame_headers_init(&frame->headers,
                              NGHTTP2_FLAG_END_HEADERS | NGHTTP2_FLAG_PRIORITY,
@@ -1536,7 +1547,8 @@ void test_nghttp2_session_on_request_headers_received(void)
   /* Check malformed headers. The library accept it. */
   nghttp2_session_server_new(&session, &callbacks, &user_data);
 
-  nvlen = nghttp2_nv_array_copy(&nva, malformed_nva, ARRLEN(malformed_nva));
+  nvlen = ARRLEN(malformed_nva);
+  nghttp2_nv_array_copy(&nva, malformed_nva, nvlen);
   nghttp2_frame_headers_init(&frame.headers,
                              NGHTTP2_FLAG_END_HEADERS | NGHTTP2_FLAG_PRIORITY,
                              1, NGHTTP2_HCAT_HEADERS, NULL, nva, nvlen);
@@ -2121,7 +2133,8 @@ void test_nghttp2_session_on_push_promise_received(void)
   stream = nghttp2_session_open_stream(session, 1, NGHTTP2_STREAM_FLAG_NONE,
                                        &pri_spec_default,
                                        NGHTTP2_STREAM_OPENING, NULL);
-  nvlen = nghttp2_nv_array_copy(&nva, malformed_nva, ARRLEN(malformed_nva));
+  nvlen = ARRLEN(malformed_nva);
+  nghttp2_nv_array_copy(&nva, malformed_nva, nvlen);
   nghttp2_frame_push_promise_init(&frame.push_promise,
                                   NGHTTP2_FLAG_END_HEADERS, 1, 2,
                                   nva, nvlen);
@@ -2386,7 +2399,7 @@ void test_nghttp2_session_send_headers_header_comp_error(void)
     nv[i].name = (uint8_t*)"header";
     nv[i].namelen = strlen((const char*)nv[i].name);
     nv[i].value = malloc(vallen+1);
-    memset(nv[i].value, '0'+i, vallen);
+    memset(nv[i].value, '0' + (int)i, vallen);
     nv[i].value[vallen] = '\0';
     nv[i].valuelen = vallen;
     nv[i].flags = NGHTTP2_NV_FLAG_NONE;
@@ -2396,7 +2409,8 @@ void test_nghttp2_session_send_headers_header_comp_error(void)
   callbacks.send_callback = null_send_callback;
 
   nghttp2_session_client_new(&session, &callbacks, NULL);
-  nvlen = nghttp2_nv_array_copy(&nva, nv, nnv);
+  nvlen = nnv;
+  nghttp2_nv_array_copy(&nva, nv, nvlen);
 
   nghttp2_frame_headers_init(&frame->headers, NGHTTP2_FLAG_END_HEADERS,
                              session->next_stream_id,
@@ -5745,7 +5759,7 @@ void test_nghttp2_session_keep_closed_stream(void)
   nghttp2_submit_settings(session, NGHTTP2_FLAG_NONE, &iv, 1);
 
   for(i = 0; i < max_concurrent_streams; ++i) {
-    open_stream(session, i * 2 + 1);
+    open_stream(session, (int)i * 2 + 1);
   }
 
   CU_ASSERT(0 == session->num_closed_streams);
diff --git a/tests/nghttp2_test_helper.c b/tests/nghttp2_test_helper.c
index 171d0648..0ab9a28f 100644
--- a/tests/nghttp2_test_helper.c
+++ b/tests/nghttp2_test_helper.c
@@ -43,7 +43,7 @@ int unpack_framebuf(nghttp2_frame *frame, nghttp2_bufs *bufs)
 
 int unpack_frame(nghttp2_frame *frame, const uint8_t *in, size_t len)
 {
-  ssize_t rv = 0;
+  int rv = 0;
   const uint8_t *payload = in + NGHTTP2_FRAME_HDLEN;
   size_t payloadlen = len - NGHTTP2_FRAME_HDLEN;
   size_t payloadoff;
@@ -187,7 +187,7 @@ ssize_t inflate_hd(nghttp2_hd_inflater *inflater, nva_out *out,
     bp = *buf;
 
     if(offset) {
-      int n;
+      ssize_t n;
 
       n = nghttp2_min((ssize_t)offset, nghttp2_buf_len(&bp));
       bp.pos += n;