GetSafeProperty: return std::string const&

Source/cmCommonTargetGenerator.cxx

@@ -77,7 +77,7 @@ void cmCommonTargetGenerator::AppendFortranFormatFlags(
   cmOutputConverter::FortranFormat format =
     cmOutputConverter::GetFortranFormat(srcfmt);
   if (format == cmOutputConverter::FortranFormatNone) {
-    const std::string tgtfmt =
+    std::string const& tgtfmt =
       this->GeneratorTarget->GetSafeProperty("Fortran_FORMAT");
     format = cmOutputConverter::GetFortranFormat(tgtfmt);
   }

Source/cmGeneratorTarget.cxx

@@ -388,14 +388,16 @@ cmProp cmGeneratorTarget::GetProperty(const std::string& prop) const
   return this->Target->GetProperty(prop);
 }
 
-const char* cmGeneratorTarget::GetSafeProperty(const std::string& prop) const
+std::string const& cmGeneratorTarget::GetSafeProperty(
+  std::string const& prop) const
 {
   cmProp ret = this->GetProperty(prop);
-  if (!ret) {
-    return "";
+  if (ret) {
+    return *ret;
   }
 
-  return ret->c_str();
+  static std::string const s_empty;
+  return s_empty;
 }
 
 const char* cmGeneratorTarget::GetOutputTargetType(
@@ -3988,7 +3990,8 @@ std::string cmGeneratorTarget::GetPchUseCompileOptions(
     const std::string useOptVar =
       cmStrCat(language, "_COMPILE_OPTIONS_USE_PCH");
 
-    const std::string useOptionListProperty = this->GetSafeProperty(useOptVar);
+    std::string const& useOptionListProperty =
+      this->GetSafeProperty(useOptVar);
 
     useOptionList = cmStrCat(
       useOptionList, ";",

Source/cmGeneratorTarget.h

@@ -80,7 +80,7 @@ public:
   //! Might return a nullptr if the property is not set or invalid
   cmProp GetProperty(const std::string& prop) const;
   //! Always returns a valid pointer
-  const char* GetSafeProperty(const std::string& prop) const;
+  std::string const& GetSafeProperty(std::string const& prop) const;
   bool GetPropertyAsBool(const std::string& prop) const;
   void GetSourceFiles(std::vector<cmSourceFile*>& files,
                       const std::string& config) const;

Source/cmGlobalGenerator.cxx

@@ -384,9 +384,9 @@ bool cmGlobalGenerator::CheckTargetsForPchCompilePdb() const
         }
       }
 
-      const std::string reuseFrom =
+      std::string const& reuseFrom =
         target->GetSafeProperty("PRECOMPILE_HEADERS_REUSE_FROM");
-      const std::string compilePdb =
+      std::string const& compilePdb =
         target->GetSafeProperty("COMPILE_PDB_NAME");
 
       if (!reuseFrom.empty() && reuseFrom != compilePdb) {

Source/cmGlobalXCodeGenerator.cxx

@@ -808,7 +808,7 @@ cmXCodeObject* cmGlobalXCodeGenerator::CreateXCodeSourceFile(
 
   // Add flags from target and source file properties.
   std::string flags;
-  const std::string srcfmt = sf->GetSafeProperty("Fortran_FORMAT");
+  std::string const& srcfmt = sf->GetSafeProperty("Fortran_FORMAT");
   switch (cmOutputConverter::GetFortranFormat(srcfmt)) {
     case cmOutputConverter::FortranFormatFixed:
       flags = "-fixed " + flags;
@@ -2289,7 +2289,7 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmGeneratorTarget* gtgt,
 
   // Add Fortran source format attribute if property is set.
   const char* format = nullptr;
-  const std::string tgtfmt = gtgt->GetSafeProperty("Fortran_FORMAT");
+  std::string const& tgtfmt = gtgt->GetSafeProperty("Fortran_FORMAT");
   switch (cmOutputConverter::GetFortranFormat(tgtfmt)) {
     case cmOutputConverter::FortranFormatFixed:
       format = "fixed";
@@ -2416,7 +2416,7 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmGeneratorTarget* gtgt,
         std::string attribute = prop.substr(16);
         this->FilterConfigurationAttribute(configName, attribute);
         if (!attribute.empty()) {
-          const std::string pr = gtgt->GetSafeProperty(prop);
+          std::string const& pr = gtgt->GetSafeProperty(prop);
           std::string processed = cmGeneratorExpression::Evaluate(
             pr, this->CurrentLocalGenerator, configName);
           buildSettings->AddAttribute(attribute,

Source/cmLocalGenerator.cxx

@@ -2670,7 +2670,8 @@ void cmLocalGenerator::AddPchDependencies(cmGeneratorTarget* target)
 
                   std::string dest_file = to_file;
 
-                  const std::string prefix = target->GetSafeProperty("PREFIX");
+                  std::string const& prefix =
+                    target->GetSafeProperty("PREFIX");
                   if (!prefix.empty()) {
                     dest_file =
                       cmStrCat(to_dir, prefix, *ReuseFrom, extension);

Source/cmQtAutoGenGlobalInitializer.cxx

@@ -95,11 +95,11 @@ cmQtAutoGenGlobalInitializer::cmQtAutoGenGlobalInitializer(
       bool const uic = target->GetPropertyAsBool(kw().AUTOUIC);
       bool const rcc = target->GetPropertyAsBool(kw().AUTORCC);
       if (moc || uic || rcc) {
-        std::string const mocExec =
+        std::string const& mocExec =
           target->GetSafeProperty(kw().AUTOMOC_EXECUTABLE);
-        std::string const uicExec =
+        std::string const& uicExec =
           target->GetSafeProperty(kw().AUTOUIC_EXECUTABLE);
-        std::string const rccExec =
+        std::string const& rccExec =
           target->GetSafeProperty(kw().AUTORCC_EXECUTABLE);
 
         // We support Qt4, Qt5 and Qt6

Source/cmQtAutoGenInitializer.cxx

@@ -440,7 +440,8 @@ bool cmQtAutoGenInitializer::InitCustomTargets()
 
     // Autogen target parallel processing
     {
-      std::string prop = this->GenTarget->GetSafeProperty("AUTOGEN_PARALLEL");
+      std::string const& prop =
+        this->GenTarget->GetSafeProperty("AUTOGEN_PARALLEL");
       if (prop.empty() || (prop == "AUTO")) {
         // Autodetect number of CPUs
         this->AutogenTarget.Parallel = GetParallelCPUCount();
@@ -471,7 +472,7 @@ bool cmQtAutoGenInitializer::InitCustomTargets()
       this->AutogenTarget.DependOrigin =
         this->GenTarget->GetPropertyAsBool("AUTOGEN_ORIGIN_DEPENDS");
 
-      std::string const deps =
+      std::string const& deps =
         this->GenTarget->GetSafeProperty("AUTOGEN_TARGET_DEPENDS");
       if (!deps.empty()) {
         for (std::string const& depName : cmExpandedList(deps)) {
@@ -654,7 +655,7 @@ bool cmQtAutoGenInitializer::InitUic()
 {
   // Uic search paths
   {
-    std::string const usp =
+    std::string const& usp =
       this->GenTarget->GetSafeProperty("AUTOUIC_SEARCH_PATHS");
     if (!usp.empty()) {
       this->Uic.SearchPaths =
@@ -1794,7 +1795,7 @@ bool cmQtAutoGenInitializer::GetQtExecutable(GenVarsT& genVars,
   // Custom executable
   {
     std::string const prop = cmStrCat(genVars.GenNameUpper, "_EXECUTABLE");
-    std::string const val = this->GenTarget->Target->GetSafeProperty(prop);
+    std::string const& val = this->GenTarget->Target->GetSafeProperty(prop);
     if (!val.empty()) {
       // Evaluate generator expression
       {

Source/cmTarget.cxx

@@ -1789,13 +1789,15 @@ cmProp cmTarget::GetProperty(const std::string& prop) const
   return retVal;
 }
 
-const char* cmTarget::GetSafeProperty(const std::string& prop) const
+std::string const& cmTarget::GetSafeProperty(std::string const& prop) const
 {
   cmProp ret = this->GetProperty(prop);
-  if (!ret) {
-    return "";
+  if (ret) {
+    return *ret;
   }
-  return ret->c_str();
+
+  static std::string const s_empty;
+  return s_empty;
 }
 
 bool cmTarget::GetPropertyAsBool(const std::string& prop) const

Source/cmTarget.h

@@ -174,7 +174,7 @@ public:
   //! Might return a nullptr if the property is not set or invalid
   cmProp GetProperty(const std::string& prop) const;
   //! Always returns a valid pointer
-  const char* GetSafeProperty(const std::string& prop) const;
+  std::string const& GetSafeProperty(std::string const& prop) const;
   bool GetPropertyAsBool(const std::string& prop) const;
   void CheckProperty(const std::string& prop, cmMakefile* context) const;
   cmProp GetComputedProperty(const std::string& prop, cmMessenger* messenger,

Source/cmVisualStudio10TargetGenerator.cxx

@@ -909,7 +909,7 @@ void cmVisualStudio10TargetGenerator::WriteDotNetReferenceCustomTags(
 
 void cmVisualStudio10TargetGenerator::WriteDotNetDocumentationFile(Elem& e0)
 {
-  std::string const documentationFile =
+  std::string const& documentationFile =
     this->GeneratorTarget->GetSafeProperty("VS_DOTNET_DOCUMENTATION_FILE");
 
   if (this->ProjectType == csproj && !documentationFile.empty()) {

Source/cmXCodeScheme.cxx

@@ -405,8 +405,9 @@ void cmXCodeScheme::WriteBuildableReference(cmXMLWriter& xout,
 void cmXCodeScheme::WriteCustomWorkingDirectory(
   cmXMLWriter& xout, const std::string& configuration)
 {
-  std::string propertyValue = this->Target->GetTarget()->GetSafeProperty(
-    "XCODE_SCHEME_WORKING_DIRECTORY");
+  std::string const& propertyValue =
+    this->Target->GetTarget()->GetSafeProperty(
+      "XCODE_SCHEME_WORKING_DIRECTORY");
   if (propertyValue.empty()) {
     xout.Attribute("useCustomWorkingDirectory", "NO");
   } else {