cmake: Factor out default generator selection into helper

Source/cmake.cxx

@@ -1313,54 +1313,7 @@ int cmake::ActualConfigure()
       cmSystemTools::SetForceUnixPaths(
         this->GlobalGenerator->GetForceUnixPaths());
     } else {
-#if defined(_WIN32) && !defined(__CYGWIN__) && !defined(CMAKE_BOOT_MINGW)
-      std::string installedCompiler;
-      // Try to find the newest VS installed on the computer and
-      // use that as a default if -G is not specified
-      const std::string vsregBase =
-        "[HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\";
-      std::vector<std::string> vsVerions;
-      vsVerions.push_back("VisualStudio\\");
-      vsVerions.push_back("VCExpress\\");
-      vsVerions.push_back("WDExpress\\");
-      struct VSRegistryEntryName
-      {
-        const char* MSVersion;
-        const char* GeneratorName;
-      };
-      VSRegistryEntryName version[] = {
-        /* clang-format needs this comment to break after the opening brace */
-        { "7.1", "Visual Studio 7 .NET 2003" },
-        { "8.0", "Visual Studio 8 2005" },
-        { "9.0", "Visual Studio 9 2008" },
-        { "10.0", "Visual Studio 10 2010" },
-        { "11.0", "Visual Studio 11 2012" },
-        { "12.0", "Visual Studio 12 2013" },
-        { "14.0", "Visual Studio 14 2015" },
-        { "15.0", "Visual Studio 15" },
-        { 0, 0 }
-      };
-      for (int i = 0; version[i].MSVersion != 0; i++) {
-        for (size_t b = 0; b < vsVerions.size(); b++) {
-          std::string reg = vsregBase + vsVerions[b] + version[i].MSVersion;
-          reg += ";InstallDir]";
-          cmSystemTools::ExpandRegistryValues(reg, cmSystemTools::KeyWOW64_32);
-          if (!(reg == "/registry")) {
-            installedCompiler = version[i].GeneratorName;
-            break;
-          }
-        }
-      }
-      cmGlobalGenerator* gen =
-        this->CreateGlobalGenerator(installedCompiler.c_str());
-      if (!gen) {
-        gen = new cmGlobalNMakeMakefileGenerator(this);
-      }
-      this->SetGlobalGenerator(gen);
-      std::cout << "-- Building for: " << gen->GetName() << "\n";
-#else
-      this->SetGlobalGenerator(new cmGlobalUnixMakefileGenerator3(this));
-#endif
+      this->CreateDefaultGlobalGenerator();
     }
     if (!this->GlobalGenerator) {
       cmSystemTools::Error("Could not create generator");
@@ -1488,6 +1441,57 @@ int cmake::ActualConfigure()
   return 0;
 }
 
+void cmake::CreateDefaultGlobalGenerator()
+{
+#if defined(_WIN32) && !defined(__CYGWIN__) && !defined(CMAKE_BOOT_MINGW)
+  std::string installedCompiler;
+  // Try to find the newest VS installed on the computer and
+  // use that as a default if -G is not specified
+  const std::string vsregBase = "[HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\";
+  std::vector<std::string> vsVerions;
+  vsVerions.push_back("VisualStudio\\");
+  vsVerions.push_back("VCExpress\\");
+  vsVerions.push_back("WDExpress\\");
+  struct VSRegistryEntryName
+  {
+    const char* MSVersion;
+    const char* GeneratorName;
+  };
+  VSRegistryEntryName version[] = {
+    /* clang-format needs this comment to break after the opening brace */
+    { "7.1", "Visual Studio 7 .NET 2003" },
+    { "8.0", "Visual Studio 8 2005" },
+    { "9.0", "Visual Studio 9 2008" },
+    { "10.0", "Visual Studio 10 2010" },
+    { "11.0", "Visual Studio 11 2012" },
+    { "12.0", "Visual Studio 12 2013" },
+    { "14.0", "Visual Studio 14 2015" },
+    { "15.0", "Visual Studio 15" },
+    { 0, 0 }
+  };
+  for (int i = 0; version[i].MSVersion != 0; i++) {
+    for (size_t b = 0; b < vsVerions.size(); b++) {
+      std::string reg = vsregBase + vsVerions[b] + version[i].MSVersion;
+      reg += ";InstallDir]";
+      cmSystemTools::ExpandRegistryValues(reg, cmSystemTools::KeyWOW64_32);
+      if (!(reg == "/registry")) {
+        installedCompiler = version[i].GeneratorName;
+        break;
+      }
+    }
+  }
+  cmGlobalGenerator* gen =
+    this->CreateGlobalGenerator(installedCompiler.c_str());
+  if (!gen) {
+    gen = new cmGlobalNMakeMakefileGenerator(this);
+  }
+  this->SetGlobalGenerator(gen);
+  std::cout << "-- Building for: " << gen->GetName() << "\n";
+#else
+  this->SetGlobalGenerator(new cmGlobalUnixMakefileGenerator3(this));
+#endif
+}
+
 void cmake::PreLoadCMakeFiles()
 {
   std::vector<std::string> args;

Source/cmake.h

@@ -500,6 +500,8 @@ private:
   // Print a list of valid generators to stderr.
   void PrintGeneratorList();
 
+  void CreateDefaultGlobalGenerator();
+
   /**
    * Convert a message type between a warning and an error, based on the state
    * of the error output CMake variables, in the cache.