Refactor: cmStandardLevelResolver::ComputeFeaturesAvailable returns cmProp

Source/cmGeneratorExpressionNode.cxx

@@ -1777,7 +1777,7 @@ static const struct CompileFeaturesNode : public cmGeneratorExpressionNode
       testedFeatures[lang].push_back(p);
 
       if (availableFeatures.find(lang) == availableFeatures.end()) {
-        const char* featuresKnown =
+        cmProp featuresKnown =
           standardResolver.CompileFeaturesAvailable(lang, &error);
         if (!featuresKnown) {
           reportError(context, content->GetOriginalExpression(), error);

Source/cmStandardLevelResolver.cxx

@@ -393,7 +393,7 @@ bool cmStandardLevelResolver::CheckCompileFeaturesAvailable(
     return true;
   }
 
-  const char* features = this->CompileFeaturesAvailable(lang, error);
+  cmProp features = this->CompileFeaturesAvailable(lang, error);
   if (!features) {
     return false;
   }
@@ -471,7 +471,7 @@ bool cmStandardLevelResolver::CompileFeatureKnown(
   return false;
 }
 
-const char* cmStandardLevelResolver::CompileFeaturesAvailable(
+cmProp cmStandardLevelResolver::CompileFeaturesAvailable(
   const std::string& lang, std::string* error) const
 {
   if (!this->Makefile->GetGlobalGenerator()->GetLanguageEnabled(lang)) {
@@ -513,7 +513,7 @@ const char* cmStandardLevelResolver::CompileFeaturesAvailable(
     }
     return nullptr;
   }
-  return cmToCStr(featuresKnown);
+  return featuresKnown;
 }
 
 bool cmStandardLevelResolver::GetNewRequiredStandard(

Source/cmStandardLevelResolver.h

@@ -30,8 +30,8 @@ public:
                            const std::string& feature, std::string& lang,
                            std::string* error) const;
 
-  const char* CompileFeaturesAvailable(const std::string& lang,
-                                       std::string* error) const;
+  cmProp CompileFeaturesAvailable(const std::string& lang,
+                                  std::string* error) const;
 
   bool GetNewRequiredStandard(const std::string& targetName,
                               const std::string& feature,