cmSystemTools: Factor out method to get Windows OS version

Factor the implementation out of `cmGlobalGenerator`.

Source/cmGlobalGenerator.cxx

@@ -49,6 +49,7 @@
 #include "cmState.h"
 #include "cmStateDirectory.h"
 #include "cmStateTypes.h"
+#include "cmSystemTools.h"
 #include "cmValue.h"
 #include "cmVersion.h"
 #include "cmWorkingDirectory.h"
@@ -62,10 +63,6 @@
 #  include "cmQtAutoGenGlobalInitializer.h"
 #endif
 
-#if defined(_MSC_VER) && _MSC_VER >= 1800
-#  define KWSYS_WINDOWS_DEPRECATED_GetVersionEx
-#endif
-
 const std::string kCMAKE_PLATFORM_INFO_INITIALIZED =
   "CMAKE_PLATFORM_INFO_INITIALIZED";
 
@@ -616,34 +613,12 @@ void cmGlobalGenerator::EnableLanguage(
   // what platform we are running on
   if (!mf->GetDefinition("CMAKE_SYSTEM")) {
 #if defined(_WIN32) && !defined(__CYGWIN__)
-    /* Windows version number data.  */
-    OSVERSIONINFOEXW osviex;
-    ZeroMemory(&osviex, sizeof(osviex));
-    osviex.dwOSVersionInfoSize = sizeof(osviex);
-
-#  ifdef KWSYS_WINDOWS_DEPRECATED_GetVersionEx
-#    pragma warning(push)
-#    ifdef __INTEL_COMPILER
-#      pragma warning(disable : 1478)
-#    elif defined __clang__
-#      pragma clang diagnostic push
-#      pragma clang diagnostic ignored "-Wdeprecated-declarations"
-#    else
-#      pragma warning(disable : 4996)
-#    endif
-#  endif
-    GetVersionExW((OSVERSIONINFOW*)&osviex);
-#  ifdef KWSYS_WINDOWS_DEPRECATED_GetVersionEx
-#    ifdef __clang__
-#      pragma clang diagnostic pop
-#    else
-#      pragma warning(pop)
-#    endif
-#  endif
+    cmSystemTools::WindowsVersion windowsVersion =
+      cmSystemTools::GetWindowsVersion();
     std::ostringstream windowsVersionString;
-    windowsVersionString << osviex.dwMajorVersion << "."
-                         << osviex.dwMinorVersion << "."
-                         << osviex.dwBuildNumber;
+    windowsVersionString << windowsVersion.dwMajorVersion << "."
+                         << windowsVersion.dwMinorVersion << "."
+                         << windowsVersion.dwBuildNumber;
     mf->AddDefinition("CMAKE_HOST_SYSTEM_VERSION", windowsVersionString.str());
 #endif
     // Read the DetermineSystem file

Source/cmSystemTools.cxx

@@ -107,6 +107,10 @@
 #  include <sys/utsname.h>
 #endif
 
+#if defined(_MSC_VER) && _MSC_VER >= 1800
+#  define CM_WINDOWS_DEPRECATED_GetVersionEx
+#endif
+
 namespace {
 
 cmSystemTools::InterruptCallback s_InterruptCallback;
@@ -904,6 +908,40 @@ cmSystemTools::WindowsFileRetry cmSystemTools::GetWindowsDirectoryRetry()
     InitWindowsDirectoryRetry().Retry;
   return retry;
 }
+
+cmSystemTools::WindowsVersion cmSystemTools::GetWindowsVersion()
+{
+  /* Windows version number data.  */
+  OSVERSIONINFOEXW osviex;
+  ZeroMemory(&osviex, sizeof(osviex));
+  osviex.dwOSVersionInfoSize = sizeof(osviex);
+
+#  ifdef CM_WINDOWS_DEPRECATED_GetVersionEx
+#    pragma warning(push)
+#    ifdef __INTEL_COMPILER
+#      pragma warning(disable : 1478)
+#    elif defined __clang__
+#      pragma clang diagnostic push
+#      pragma clang diagnostic ignored "-Wdeprecated-declarations"
+#    else
+#      pragma warning(disable : 4996)
+#    endif
+#  endif
+  GetVersionExW((OSVERSIONINFOW*)&osviex);
+#  ifdef CM_WINDOWS_DEPRECATED_GetVersionEx
+#    ifdef __clang__
+#      pragma clang diagnostic pop
+#    else
+#      pragma warning(pop)
+#    endif
+#  endif
+
+  WindowsVersion result;
+  result.dwMajorVersion = osviex.dwMajorVersion;
+  result.dwMinorVersion = osviex.dwMinorVersion;
+  result.dwBuildNumber = osviex.dwBuildNumber;
+  return result;
+}
 #endif
 
 std::string cmSystemTools::GetRealPathResolvingWindowsSubst(

Source/cmSystemTools.h

@@ -509,6 +509,14 @@ public:
   };
   static WindowsFileRetry GetWindowsFileRetry();
   static WindowsFileRetry GetWindowsDirectoryRetry();
+
+  struct WindowsVersion
+  {
+    unsigned int dwMajorVersion;
+    unsigned int dwMinorVersion;
+    unsigned int dwBuildNumber;
+  };
+  static WindowsVersion GetWindowsVersion();
 #endif
 
   /** Get the real path for a given path, removing all symlinks.