diff --git a/clickhouse/CMakeLists.txt b/clickhouse/CMakeLists.txt
index 67663ec5..ec544e1b 100644
--- a/clickhouse/CMakeLists.txt
+++ b/clickhouse/CMakeLists.txt
@@ -34,6 +34,21 @@ SET ( clickhouse-cpp-lib-src
     query.cpp
 )
 
+if (MSVC)
+    add_definitions(-D_CRT_SECURE_NO_WARNINGS)
+    add_compile_options(/W4)
+    # remove in 3.0
+    add_compile_options(/wd4996)
+else()
+    set(cxx_extra_wall "-Wempty-body -Wconversion -Wreturn-type -Wparentheses -Wuninitialized -Wunreachable-code -Wunused-function -Wunused-value -Wunused-variable")   
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${cxx_extra_wall}")
+
+    if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" OR CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
+        # a little abnormal when clang check conversion
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${cxx_extra_wall} -Wno-conversion")
+    endif()
+endif()
+
 IF (WITH_OPENSSL)
     LIST(APPEND clickhouse-cpp-lib-src base/sslsocket.cpp)
 ENDIF ()
diff --git a/clickhouse/base/compressed.cpp b/clickhouse/base/compressed.cpp
index 4d5cc65d..135f9483 100644
--- a/clickhouse/base/compressed.cpp
+++ b/clickhouse/base/compressed.cpp
@@ -94,7 +94,7 @@ bool CompressedInput::Decompress() {
 
         data_ = Buffer(original);
 
-        if (LZ4_decompress_safe((const char*)tmp.data() + HEADER_SIZE, (char*)data_.data(), compressed - HEADER_SIZE, original) < 0) {
+        if (LZ4_decompress_safe((const char*)tmp.data() + HEADER_SIZE, (char*)data_.data(), static_cast<int>(compressed - HEADER_SIZE), original) < 0) {
             throw LZ4Error("can't decompress data");
         } else {
             mem_.Reset(data_.data(), original);
@@ -141,7 +141,7 @@ void CompressedOutput::Compress(const void * data, size_t len) {
     const auto compressed_size = LZ4_compress_default(
             (const char*)data,
             (char*)compressed_buffer_.data() + HEADER_SIZE,
-            len,
+            static_cast<int>(len),
             static_cast<int>(compressed_buffer_.size() - HEADER_SIZE));
     if (compressed_size <= 0)
         throw LZ4Error("Failed to compress chunk of " + std::to_string(len) + " bytes, "
diff --git a/clickhouse/base/socket.cpp b/clickhouse/base/socket.cpp
index 48e90c73..7d7326a4 100644
--- a/clickhouse/base/socket.cpp
+++ b/clickhouse/base/socket.cpp
@@ -217,7 +217,7 @@ SOCKET SocketConnect(const NetworkAddress& addr, const SocketTimeoutParams& time
                 fd.fd = *s;
                 fd.events = POLLOUT;
                 fd.revents = 0;
-                ssize_t rval = Poll(&fd, 1, timeout_params.connect_timeout.count());
+                ssize_t rval = Poll(&fd, 1, static_cast<int>(timeout_params.connect_timeout.count()));
 
                 if (rval == -1) {
                     throw std::system_error(getSocketErrorCode(), getErrorCategory(), "fail to connect");
diff --git a/clickhouse/base/sslsocket.cpp b/clickhouse/base/sslsocket.cpp
index 8b1971e0..4c5185d8 100644
--- a/clickhouse/base/sslsocket.cpp
+++ b/clickhouse/base/sslsocket.cpp
@@ -109,7 +109,7 @@ SSL_CTX * prepareSSLContext(const clickhouse::SSLParams & context_params) {
 
 #define HANDLE_SSL_CTX_ERROR(statement) do { \
     if (const auto ret_code = (statement); !ret_code) \
-        throwSSLError(nullptr, ERR_peek_error(), LOCATION, #statement); \
+        throwSSLError(nullptr, static_cast<int>(ERR_peek_error()), LOCATION, #statement); \
 } while(false);
 
     if (context_params.use_default_ca_locations)
@@ -185,7 +185,7 @@ SSL_CTX * SSLContext::getContext() {
 // Allows caller to use returned value of `statement` if there was no error, throws exception otherwise.
 #define HANDLE_SSL_ERROR(SSL_PTR, statement) [&] { \
     if (const auto ret_code = (statement); ret_code <= 0) { \
-        throwSSLError(SSL_PTR, SSL_get_error(SSL_PTR, ret_code), LOCATION, #statement); \
+        throwSSLError(SSL_PTR, SSL_get_error(SSL_PTR, static_cast<int>(ret_code)), LOCATION, #statement); \
         return static_cast<std::decay_t<decltype(ret_code)>>(0); \
     } \
     else \
@@ -209,7 +209,7 @@ SSLSocket::SSLSocket(const NetworkAddress& addr, const SocketTimeoutParams& time
 
     std::unique_ptr<ASN1_OCTET_STRING, decltype(&ASN1_OCTET_STRING_free)> ip_addr(a2i_IPADDRESS(addr.Host().c_str()), &ASN1_OCTET_STRING_free);
 
-    HANDLE_SSL_ERROR(ssl, SSL_set_fd(ssl, handle_));
+    HANDLE_SSL_ERROR(ssl, SSL_set_fd(ssl, static_cast<int>(handle_)));
     if (ssl_params.use_SNI)
         HANDLE_SSL_ERROR(ssl, SSL_set_tlsext_host_name(ssl, addr.Host().c_str()));
 
@@ -295,7 +295,11 @@ SSLSocketOutput::SSLSocketOutput(SSL *ssl)
 {}
 
 size_t SSLSocketOutput::DoWrite(const void* data, size_t len) {
-    return static_cast<size_t>(HANDLE_SSL_ERROR(ssl_, SSL_write(ssl_, data, len)));
+    if (len > std::numeric_limits<int>::max())
+        // FIXME(vnemkov): We should do multiple `SSL_write`s in this case.
+        throw AssertionError("Failed to write too big chunk at once "
+                + std::to_string(len) + " > " + std::to_string(std::numeric_limits<int>::max()));
+    return static_cast<size_t>(HANDLE_SSL_ERROR(ssl_, SSL_write(ssl_, data, static_cast<int>(len))));
 }
 
 #undef HANDLE_SSL_ERROR
diff --git a/clickhouse/client.cpp b/clickhouse/client.cpp
index e4b0c7ef..2f675da0 100644
--- a/clickhouse/client.cpp
+++ b/clickhouse/client.cpp
@@ -411,12 +411,12 @@ bool Client::Impl::ReceivePacket(uint64_t* server_packet) {
         if (!WireFormat::ReadUInt64(*input_, &info.bytes)) {
             return false;
         }
-        if (REVISION >= DBMS_MIN_REVISION_WITH_TOTAL_ROWS_IN_PROGRESS) {
+        if constexpr(REVISION >= DBMS_MIN_REVISION_WITH_TOTAL_ROWS_IN_PROGRESS) {
             if (!WireFormat::ReadUInt64(*input_, &info.total_rows)) {
                 return false;
             }
         }
-        if (REVISION >= DBMS_MIN_REVISION_WITH_CLIENT_WRITE_INFO)
+        if constexpr (REVISION >= DBMS_MIN_REVISION_WITH_CLIENT_WRITE_INFO)
         {
             if (!WireFormat::ReadUInt64(*input_, &info.written_rows)) {
                 return false;
@@ -499,13 +499,11 @@ bool Client::Impl::ReceivePacket(uint64_t* server_packet) {
         throw UnimplementedError("unimplemented " + std::to_string((int)packet_type));
         break;
     }
-
-    return false;
 }
 
 bool Client::Impl::ReadBlock(InputStream& input, Block* block) {
     // Additional information about block.
-    if (REVISION >= DBMS_MIN_REVISION_WITH_BLOCK_INFO) {
+    if constexpr (REVISION >= DBMS_MIN_REVISION_WITH_BLOCK_INFO) {
         uint64_t num;
         BlockInfo info;
 
@@ -569,7 +567,7 @@ bool Client::Impl::ReadBlock(InputStream& input, Block* block) {
 bool Client::Impl::ReceiveData() {
     Block block;
 
-    if (REVISION >= DBMS_MIN_REVISION_WITH_TEMPORARY_TABLES) {
+    if constexpr (REVISION >= DBMS_MIN_REVISION_WITH_TEMPORARY_TABLES) {
         if (!WireFormat::SkipString(*input_)) {
             return false;
         }
diff --git a/clickhouse/columns/enum.cpp b/clickhouse/columns/enum.cpp
index 1361e817..cd7696ca 100644
--- a/clickhouse/columns/enum.cpp
+++ b/clickhouse/columns/enum.cpp
@@ -30,7 +30,7 @@ void ColumnEnum<T>::Append(const T& value, bool checkValue) {
 
 template <typename T>
 void ColumnEnum<T>::Append(const std::string& name) {
-    data_.push_back(type_->As<EnumType>()->GetEnumValue(name));
+    data_.push_back(static_cast<T>(type_->As<EnumType>()->GetEnumValue(name)));
 }
 
 template <typename T>
@@ -63,7 +63,7 @@ void ColumnEnum<T>::SetAt(size_t n, const T& value, bool checkValue) {
 
 template <typename T>
 void ColumnEnum<T>::SetNameAt(size_t n, const std::string& name) {
-    data_.at(n) = type_->As<EnumType>()->GetEnumValue(name);
+    data_.at(n) = static_cast<T>(type_->As<EnumType>()->GetEnumValue(name));
 }
 
 template <typename T>
diff --git a/clickhouse/columns/factory.cpp b/clickhouse/columns/factory.cpp
index e003b7f5..aeacdabc 100644
--- a/clickhouse/columns/factory.cpp
+++ b/clickhouse/columns/factory.cpp
@@ -38,7 +38,7 @@ const auto& GetASTChildElement(const TypeAst & ast, int position) {
         throw ValidationError("AST child element index out of bounds: " + std::to_string(position));
 
     if (position < 0)
-        position = ast.elements.size() + position;
+        position = static_cast<int>(ast.elements.size() + position);
 
     return ast.elements[static_cast<size_t>(position)];
 }
diff --git a/clickhouse/columns/lowcardinality.cpp b/clickhouse/columns/lowcardinality.cpp
index d3627038..13bf17a1 100644
--- a/clickhouse/columns/lowcardinality.cpp
+++ b/clickhouse/columns/lowcardinality.cpp
@@ -199,7 +199,7 @@ std::uint64_t ColumnLowCardinality::getDictionaryIndex(std::uint64_t item_index)
 void ColumnLowCardinality::appendIndex(std::uint64_t item_index) {
     // TODO (nemkov): handle case when index should go from UInt8 to UInt16, etc.
     VisitIndexColumn([item_index](auto & arg) {
-        arg.Append(item_index);
+        arg.Append(static_cast<typename std::decay_t<decltype(arg)>::DataType>(item_index));
     }, *index_column_);
 }