From c0cf425074e8cd0395320b659e254ba628a7c78c Mon Sep 17 00:00:00 2001
From: Ben Adams <thundercat@illyriad.co.uk>
Date: Mon, 31 Dec 2018 06:22:08 +0100
Subject: [PATCH] Remove Environment static constructor (dotnet/coreclr#21715)

Commit migrated from https://github.com/dotnet/coreclr/commit/6a989431e5a8c5d9113b6d03a4aa9a15b6653655
---
 .../src/System/Environment.cs                      | 65 +++++++++++++---------
 1 file changed, 39 insertions(+), 26 deletions(-)

diff --git a/src/coreclr/src/System.Private.CoreLib/src/System/Environment.cs b/src/coreclr/src/System.Private.CoreLib/src/System/Environment.cs
index e94f62c..488da3b 100644
--- a/src/coreclr/src/System.Private.CoreLib/src/System/Environment.cs
+++ b/src/coreclr/src/System.Private.CoreLib/src/System/Environment.cs
@@ -186,7 +186,7 @@ namespace System
         [MethodImplAttribute(MethodImplOptions.InternalCall)]
         private static extern string[] GetCommandLineArgsNative();
 
-        private static string[] s_CommandLineArgs = null;
+        private static string[] s_CommandLineArgs;
         private static void SetCommandLineArgs(string[] cmdLineArgs)
         {
             s_CommandLineArgs = cmdLineArgs;
@@ -272,39 +272,52 @@ namespace System
         }
 
 #if !FEATURE_PAL
-        private static Lazy<bool> s_IsWindows8OrAbove = new Lazy<bool>(() => 
+        internal static bool IsWindows8OrAbove => WindowsVersion.IsWindows8OrAbove;
+
+        // Seperate type so a .cctor is not created for Enviroment which then would be triggered during startup
+        private static class WindowsVersion
         {
-            unsafe
-            {
-                ulong conditionMask = Win32Native.VerSetConditionMask(0, Win32Native.VER_MAJORVERSION, Win32Native.VER_GREATER_EQUAL);
-                conditionMask = Win32Native.VerSetConditionMask(conditionMask, Win32Native.VER_MINORVERSION, Win32Native.VER_GREATER_EQUAL);
-                conditionMask = Win32Native.VerSetConditionMask(conditionMask, Win32Native.VER_SERVICEPACKMAJOR, Win32Native.VER_GREATER_EQUAL);
-                conditionMask = Win32Native.VerSetConditionMask(conditionMask, Win32Native.VER_SERVICEPACKMINOR, Win32Native.VER_GREATER_EQUAL);
+            // Cache the value in readonly static that can be optimized out by the JIT
+            internal readonly static bool IsWindows8OrAbove = GetIsWindows8OrAbove();
 
-                // Windows 8 version is 6.2
-                var version = new Win32Native.OSVERSIONINFOEX();
-                version.dwOSVersionInfoSize = sizeof(Win32Native.OSVERSIONINFOEX);
-                version.dwMajorVersion = 6;
-                version.dwMinorVersion = 2;
-                version.wServicePackMajor = 0;
-                version.wServicePackMinor = 0;
+            private static bool GetIsWindows8OrAbove()
+            {
+                bool isWindows8OrAbove;
+                unsafe
+                {
+                    ulong conditionMask = Win32Native.VerSetConditionMask(0, Win32Native.VER_MAJORVERSION, Win32Native.VER_GREATER_EQUAL);
+                    conditionMask = Win32Native.VerSetConditionMask(conditionMask, Win32Native.VER_MINORVERSION, Win32Native.VER_GREATER_EQUAL);
+                    conditionMask = Win32Native.VerSetConditionMask(conditionMask, Win32Native.VER_SERVICEPACKMAJOR, Win32Native.VER_GREATER_EQUAL);
+                    conditionMask = Win32Native.VerSetConditionMask(conditionMask, Win32Native.VER_SERVICEPACKMINOR, Win32Native.VER_GREATER_EQUAL);
+
+                    // Windows 8 version is 6.2
+                    var version = new Win32Native.OSVERSIONINFOEX();
+                    version.dwOSVersionInfoSize = sizeof(Win32Native.OSVERSIONINFOEX);
+                    version.dwMajorVersion = 6;
+                    version.dwMinorVersion = 2;
+                    version.wServicePackMajor = 0;
+                    version.wServicePackMinor = 0;
+
+                    isWindows8OrAbove = Win32Native.VerifyVersionInfoW(ref version,
+                               Win32Native.VER_MAJORVERSION | Win32Native.VER_MINORVERSION | Win32Native.VER_SERVICEPACKMAJOR | Win32Native.VER_SERVICEPACKMINOR,
+                               conditionMask);
+                }
 
-                return Win32Native.VerifyVersionInfoW(ref version,
-                           Win32Native.VER_MAJORVERSION | Win32Native.VER_MINORVERSION | Win32Native.VER_SERVICEPACKMAJOR | Win32Native.VER_SERVICEPACKMINOR,
-                           conditionMask);
+                return isWindows8OrAbove;
             }
-        });
-        internal static bool IsWindows8OrAbove => s_IsWindows8OrAbove.Value;
+        }
 #endif
-        
+
 #if FEATURE_COMINTEROP
-        // Does the current version of Windows have Windows Runtime suppport?
-        private static Lazy<bool> s_IsWinRTSupported = new Lazy<bool>(() =>
+        // Seperate type so a .cctor is not created for Enviroment which then would be triggered during startup
+        private static class WinRT
         {
-            return WinRTSupported();
-        });
+            // Cache the value in readonly static that can be optimized out by the JIT
+            public readonly static bool IsSupported = WinRTSupported();
+        }
 
-        internal static bool IsWinRTSupported => s_IsWinRTSupported.Value;
+        // Does the current version of Windows have Windows Runtime suppport?
+        internal static bool IsWinRTSupported => WinRT.IsSupported;
 
         [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
         [return: MarshalAs(UnmanagedType.Bool)]
-- 
2.7.4