diff --git a/json.cpp b/json.cpp
index 571eaa9..521b5fe 100644
--- a/json.cpp
+++ b/json.cpp
@@ -92,7 +92,7 @@ const JSON &JSON::at(unsigned int index) const {
 
 int JSON::length() const {
     if( Type == Class::Array )
-        return Internal.List->size();
+        return static_cast<int>(Internal.List->size());
     else
         return -1;
 }
@@ -105,9 +105,9 @@ bool JSON::hasKey(const std::string &key) const {
 
 int JSON::size() const {
     if( Type == Class::Object )
-        return Internal.Map->size();
+        return static_cast<int>(Internal.Map->size());
     else if( Type == Class::Array )
-        return Internal.List->size();
+        return static_cast<int>(Internal.List->size());
     else
         return -1;
 }
diff --git a/lib/windows-x86_64/rktwebview.lib b/lib/windows-x86_64/rktwebview.lib
new file mode 100644
index 0000000..94ee101
Binary files /dev/null and b/lib/windows-x86_64/rktwebview.lib differ
diff --git a/main.cpp b/main.cpp
index f6d0895..b20cd83 100644
--- a/main.cpp
+++ b/main.cpp
@@ -63,6 +63,7 @@ static void event_cb(rkt_data_t *data)
     free_data(data);
 }
 
+
 int main(int argc, char *argv[])
 {
     const char *me = argv[0];
diff --git a/rktwebview.cpp b/rktwebview.cpp
index 6621dec..6abd1fa 100644
--- a/rktwebview.cpp
+++ b/rktwebview.cpp
@@ -31,6 +31,10 @@
 #define ALIVE_SLOT          4
 #define ALIVE_ACK_SLOT      5
 
+#ifdef _WIN32
+#define strdup _strdup
+#endif
+
 //#define DEBUG
 
 /////////////////////////////////////////////////////////////////////
@@ -106,12 +110,12 @@ bool runRktWebview(Handle_t *handler)
     char alive_slot[10];
     char alive_ack_slot[10];
 
-    sprintf(shm_size_str, "%d", static_cast<int>(handler->shm_size));
-    sprintf(command_slot, "%d", COMMAND_SLOT);
-    sprintf(command_result_slot, "%d", COMMAND_RESULT_SLOT);
-    sprintf(event_slot, "%d", EVENT_SLOT);
-    sprintf(alive_slot, "%d", ALIVE_SLOT);
-    sprintf(alive_ack_slot, "%d", ALIVE_ACK_SLOT);
+    snprintf(shm_size_str, 30, "%d", static_cast<int>(handler->shm_size));
+    snprintf(command_slot, 10, "%d", COMMAND_SLOT);
+    snprintf(command_result_slot, 10, "%d", COMMAND_RESULT_SLOT);
+    snprintf(event_slot, 10, "%d", EVENT_SLOT);
+    snprintf(alive_slot, 10, "%d", ALIVE_SLOT);
+    snprintf(alive_ack_slot, 10, "%d", ALIVE_ACK_SLOT);
 
 
     // run rktwebview_prg using the environment variable RKT_WEBVIEW_PRG
@@ -316,7 +320,7 @@ void rkt_webview_init()
 #else
 #ifdef _WIN32
         DWORD p = GetCurrentProcessId();
-        sprintf(buf, "rktwebview-%ld", p);
+        snprintf(buf, 1024, "rktwebview-%ld", p);
 #else
         pid_t p = getpid();
         sprintf(buf, "rktwebview-%x", p);
diff --git a/shm.cpp b/shm.cpp
index 9c8642e..cd9c280 100644
--- a/shm.cpp
+++ b/shm.cpp
@@ -138,7 +138,7 @@ public:
                 first_i->prev = p_i;
             }
             i->prev = SHM_NULL;
-            i->alloc_size = bytes;
+            i->alloc_size = static_cast<int>(bytes);
 
             *_first = p_i;
             place = p_i + sizeof(ShmItem);
@@ -152,8 +152,8 @@ public:
             } else {
                 *_used = u;
                 i->prev = SHM_NULL;
-                i->size = bytes;
-                i->alloc_size = bytes;
+                i->size = static_cast<int>(bytes);
+                i->alloc_size = static_cast<int>(bytes);
                 i->next = *_first;
                 if (*_first != SHM_NULL) {
                     ShmItem *first_i;
@@ -180,6 +180,7 @@ public:
         ShmPlace p_i = place - sizeof(ShmItem);
         ShmItem *i;
         ref(p_i, &i);
+        if (i == nullptr) return;
 
         if (i->prev != SHM_NULL) {
             ShmItem *prev_i;
@@ -218,8 +219,9 @@ public:
 
 public:
     ShmApiBase(const char *name, size_t size, bool owner) {
-        char *buf = reinterpret_cast<char *>(malloc(strlen(name) + 50));
-        sprintf(buf, "sem_%s", name);
+        size_t buf_size = strlen(name) + 50;
+        char *buf = reinterpret_cast<char *>(malloc(buf_size));
+        snprintf(buf, buf_size, "sem_%s", name);
         _sem_name = _strdup(buf);
         _mem_name = _strdup(name);
         ::free(buf);
@@ -495,7 +497,7 @@ public:
             if (_owner) {
                 *_first = SHM_NULL;
                 *_free_list = SHM_NULL;
-                *_used = sizeof(int) + sizeof(ShmItem *) + sizeof(ShmItem *) + slots_size;
+                *_used = static_cast<int>(sizeof(int) + sizeof(ShmItem *) + sizeof(ShmItem *) + slots_size);
             }
         }
     }
diff --git a/shmqueue.cpp b/shmqueue.cpp
index 514d418..d5ed712 100644
--- a/shmqueue.cpp
+++ b/shmqueue.cpp
@@ -1,6 +1,10 @@
 #include "shmqueue.h"
 #include <string.h>
 
+#ifdef _WIN32
+#define sprintf sprintf_s
+#endif
+
 ShmQueue::ShmQueue(Shm *shm, ShmSlot slot, bool owner)
 {
     _shm = shm;