diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7c413de5..307c0fb9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.6)
+cmake_minimum_required(VERSION 3.8)
 project(calculator CXX)
 set(CMAKE_CXX_STANDARD 17)
 
diff --git a/src/CalcManager/CEngine/Number.cpp b/src/CalcManager/CEngine/Number.cpp
index b445fed2..4bf83a33 100644
--- a/src/CalcManager/CEngine/Number.cpp
+++ b/src/CalcManager/CEngine/Number.cpp
@@ -59,13 +59,6 @@ namespace CalcEngine
 
     bool Number::IsZero() const
     {
-        for (auto const& digit : Mantissa())
-        {
-            if (digit != 0)
-            {
-                return false;
-            }
-        }
-        return true;
+        return all_of(m_mantissa.begin(), m_mantissa.end(), [](auto &&i) { return i == 0; });
     }
 }
diff --git a/src/CalcManager/CEngine/calc.cpp b/src/CalcManager/CEngine/calc.cpp
index 00fa2b45..210b2023 100644
--- a/src/CalcManager/CEngine/calc.cpp
+++ b/src/CalcManager/CEngine/calc.cpp
@@ -18,8 +18,8 @@ static constexpr int32_t DEFAULT_RADIX = 10;
 
 static constexpr wchar_t DEFAULT_DEC_SEPARATOR = L'.';
 static constexpr wchar_t DEFAULT_GRP_SEPARATOR = L',';
-static const wstring_view DEFAULT_GRP_STR = L"3;0";
-static const wstring_view DEFAULT_NUMBER_STR = L"0";
+static constexpr wstring_view DEFAULT_GRP_STR = L"3;0";
+static constexpr wstring_view DEFAULT_NUMBER_STR = L"0";
 
 // Read strings for keys, errors, trig types, etc.
 // These will be copied from the resources to local memory.
diff --git a/src/CalcManager/CEngine/scidisp.cpp b/src/CalcManager/CEngine/scidisp.cpp
index e099b3b4..64af7593 100644
--- a/src/CalcManager/CEngine/scidisp.cpp
+++ b/src/CalcManager/CEngine/scidisp.cpp
@@ -21,8 +21,8 @@ using namespace CalcEngine;
 
 constexpr int MAX_EXPONENT = 4;
 constexpr uint32_t MAX_GROUPING_SIZE = 16;
-const wstring_view c_decPreSepStr = L"[+-]?(\\d*)[";
-const wstring_view c_decPostSepStr = L"]?(\\d*)(?:e[+-]?(\\d*))?$";
+constexpr wstring_view c_decPreSepStr = L"[+-]?(\\d*)[";
+constexpr wstring_view c_decPostSepStr = L"]?(\\d*)(?:e[+-]?(\\d*))?$";
 
 
 /****************************************************************************\
diff --git a/src/CalcManager/Header Files/EngineStrings.h b/src/CalcManager/Header Files/EngineStrings.h
index 2e58c283..d358766d 100644
--- a/src/CalcManager/Header Files/EngineStrings.h	
+++ b/src/CalcManager/Header Files/EngineStrings.h	
@@ -219,7 +219,7 @@
 #define SIDS_ERR_INPUT_OVERFLOW L"119"
 #define SIDS_ERR_OUTPUT_OVERFLOW L"120"
 
-__declspec(selectany) std::wstring g_sids[] =
+DECLSPEC_SELECTANY std::wstring g_sids[] =
 {
     std::wstring(SIDS_PLUS_MINUS),
     std::wstring(SIDS_C),
diff --git a/src/CalcManager/pch.h b/src/CalcManager/pch.h
index 843e8a01..6073de5a 100644
--- a/src/CalcManager/pch.h
+++ b/src/CalcManager/pch.h
@@ -25,7 +25,7 @@
 #include <array>
 #include <string_view>
 
-#ifdef _WIN32
+#if defined(_WIN32) && defined(_MSC_VER)
 
 #include <windows.h>
 #include <winerror.h>
@@ -41,4 +41,10 @@
 #include "win_data_types_cross_platform.h"
 #include "sal_cross_platform.h"
 
+#ifdef __GNUC__
+#define DECLSPEC_SELECTANY __attribute__((selectany))
+#else
+#define DECLSPEC_SELECTANY __declspec(selectany)
+#endif
+
 #endif
diff --git a/src/CalcManager/sal_cross_platform.h b/src/CalcManager/sal_cross_platform.h
index cc650f17..c89e37d4 100644
--- a/src/CalcManager/sal_cross_platform.h
+++ b/src/CalcManager/sal_cross_platform.h
@@ -8,3 +8,4 @@
 #define _Out_
 #define _Inout_
 #define __in_opt
+#define _Frees_ptr_opt_