Merge pull request #180 from microsoft/dev/gcampbell/Update

Update compatibility

Author: gcampbell-msft

Source/cmGlobalVisualStudioVersionedGenerator.cxx

@@ -505,7 +505,10 @@ bool cmGlobalVisualStudioVersionedGenerator::SetGeneratorInstance(
   }
 
   if (!this->GeneratorInstanceVersion.empty()) {
-    std::string const majorStr = VSVersionToMajorString(this->Version);
+    std::string majorStr = VSVersionToMajorString(this->Version);
+    if (majorStr == "17" && this->GeneratorInstanceVersion._Starts_with("18")) {
+      majorStr = "18";
+    }
     cmsys::RegularExpression versionRegex(
       cmStrCat('^', majorStr, R"(\.[0-9]+\.[0-9]+\.[0-9]+$)"));
     if (!versionRegex.find(this->GeneratorInstanceVersion)) {

Source/cmVSSetupHelper.cxx

@@ -459,7 +459,8 @@ bool cmVSSetupAPIHelper::EnumerateAndChooseVSInstance()
   for (const auto& instanceInfo : vecVSInstancesAll) {
     // We are looking for a specific major version.
     if (instanceInfo.Version.size() < wantVersion.size() ||
-        instanceInfo.Version.substr(0, wantVersion.size()) != wantVersion) {
+        (instanceInfo.Version.substr(0, wantVersion.size()) != wantVersion &&
+        !(instanceInfo.Version.substr(0, wantVersion.size()) == "18." && wantVersion == "17."))) {
       continue;
     }