diff --git a/Source/cmAddCustomCommandCommand.cxx b/Source/cmAddCustomCommandCommand.cxx
index 46067d1dc6..85a807b049 100644
--- a/Source/cmAddCustomCommandCommand.cxx
+++ b/Source/cmAddCustomCommandCommand.cxx
@@ -9,6 +9,7 @@
 #include <utility>
 
 #include <cm/memory>
+#include <cm/optional>
 #include <cmext/string_view>
 
 #include "cmCustomCommand.h"
@@ -44,8 +45,7 @@ bool cmAddCustomCommandCommand(std::vector<std::string> const& args,
   std::string depfile;
   std::string job_pool;
   std::string job_server_aware;
-  std::string comment_buffer;
-  char const* comment = nullptr;
+  cm::optional<std::string> comment;
   std::vector<std::string> depends;
   std::vector<std::string> outputs;
   std::vector<std::string> output;
@@ -369,7 +369,7 @@ bool cmAddCustomCommandCommand(std::vector<std::string> const& args,
           byproducts.push_back(filename);
           break;
         case doing_comment:
-          if (!comment_buffer.empty()) {
+          if (comment && !comment->empty()) {
             std::string const msg =
               "COMMENT requires exactly one argument, but multiple values "
               "or COMMENT keywords have been given.";
@@ -381,8 +381,7 @@ bool cmAddCustomCommandCommand(std::vector<std::string> const& args,
               mf.IssuePolicyWarning(cmPolicies::CMP0175, msg);
             }
           }
-          comment_buffer = copy;
-          comment = comment_buffer.c_str();
+          comment = copy;
           break;
         default:
           status.SetError("Wrong syntax. Unknown type of argument.");
@@ -477,7 +476,7 @@ bool cmAddCustomCommandCommand(std::vector<std::string> const& args,
   cc->SetByproducts(byproducts);
   cc->SetCommandLines(commandLines);
   cc->SetComment(comment);
-  cc->SetWorkingDirectory(working.c_str());
+  cc->SetWorkingDirectory(working);
   cc->SetEscapeOldStyle(!verbatim);
   cc->SetUsesTerminal(uses_terminal);
   cc->SetDepfile(depfile);
diff --git a/Source/cmAddCustomTargetCommand.cxx b/Source/cmAddCustomTargetCommand.cxx
index 92bc25e077..b2da4e0739 100644
--- a/Source/cmAddCustomTargetCommand.cxx
+++ b/Source/cmAddCustomTargetCommand.cxx
@@ -5,6 +5,7 @@
 #include <utility>
 
 #include <cm/memory>
+#include <cm/optional>
 
 #include "cmCustomCommand.h"
 #include "cmCustomCommandLines.h"
@@ -50,8 +51,7 @@ bool cmAddCustomTargetCommand(std::vector<std::string> const& args,
   bool verbatim = false;
   bool uses_terminal = false;
   bool command_expand_lists = false;
-  std::string comment_buffer;
-  char const* comment = nullptr;
+  cm::optional<std::string> comment;
   std::vector<std::string> sources;
   std::string job_pool;
   std::string job_server_aware;
@@ -143,8 +143,7 @@ bool cmAddCustomTargetCommand(std::vector<std::string> const& args,
           depends.push_back(std::move(dep));
         } break;
         case doing_comment:
-          comment_buffer = copy;
-          comment = comment_buffer.c_str();
+          comment = copy;
           break;
         case doing_source:
           sources.push_back(copy);
@@ -209,7 +208,7 @@ bool cmAddCustomTargetCommand(std::vector<std::string> const& args,
 
   // Add the utility target to the makefile.
   auto cc = cm::make_unique<cmCustomCommand>();
-  cc->SetWorkingDirectory(working_directory.c_str());
+  cc->SetWorkingDirectory(working_directory);
   cc->SetByproducts(byproducts);
   cc->SetDepends(depends);
   cc->SetCommandLines(commandLines);
diff --git a/Source/cmArgumentParser.cxx b/Source/cmArgumentParser.cxx
index 30bdadc074..97c2d2a02f 100644
--- a/Source/cmArgumentParser.cxx
+++ b/Source/cmArgumentParser.cxx
@@ -127,7 +127,8 @@ void Instance::Bind(NonEmpty<std::vector<std::string>>& val)
     ExpectAtLeast{ 1 });
 }
 
-void Instance::Bind(std::vector<std::vector<std::string>>& multiVal)
+void Instance::Bind(
+  MaybeEmpty<std::vector<std::vector<std::string>>>& multiVal)
 {
   multiVal.emplace_back();
   std::vector<std::string>& val = multiVal.back();
@@ -139,6 +140,18 @@ void Instance::Bind(std::vector<std::vector<std::string>>& multiVal)
     ExpectAtLeast{ 0 });
 }
 
+void Instance::Bind(NonEmpty<std::vector<std::vector<std::string>>>& multiVal)
+{
+  multiVal.emplace_back();
+  std::vector<std::string>& val = multiVal.back();
+  this->Bind(
+    [&val](cm::string_view arg) -> Continue {
+      val.emplace_back(arg);
+      return Continue::Yes;
+    },
+    ExpectAtLeast{ 1 });
+}
+
 void Instance::Consume(cm::string_view arg)
 {
   ParserState& state = this->GetState();
diff --git a/Source/cmArgumentParser.h b/Source/cmArgumentParser.h
index 6bc22503b5..7b378551ae 100644
--- a/Source/cmArgumentParser.h
+++ b/Source/cmArgumentParser.h
@@ -228,7 +228,8 @@ public:
   void Bind(Maybe<std::string>& val);
   void Bind(MaybeEmpty<std::vector<std::string>>& val);
   void Bind(NonEmpty<std::vector<std::string>>& val);
-  void Bind(std::vector<std::vector<std::string>>& val);
+  void Bind(MaybeEmpty<std::vector<std::vector<std::string>>>& val);
+  void Bind(NonEmpty<std::vector<std::vector<std::string>>>& val);
 
   template <typename U>
   void Bind(NonEmpty<std::vector<std::pair<std::string, U>>>& val,
diff --git a/Source/cmCustomCommand.cxx b/Source/cmCustomCommand.cxx
index 5ec451efbd..b7b40a9bf7 100644
--- a/Source/cmCustomCommand.cxx
+++ b/Source/cmCustomCommand.cxx
@@ -77,16 +77,14 @@ void cmCustomCommand::SetCommandLines(cmCustomCommandLines commandLines)
   this->CommandLines = std::move(commandLines);
 }
 
-char const* cmCustomCommand::GetComment() const
+cm::optional<std::string> const& cmCustomCommand::GetComment() const
 {
-  char const* no_comment = nullptr;
-  return this->HaveComment ? this->Comment.c_str() : no_comment;
+  return this->Comment;
 }
 
-void cmCustomCommand::SetComment(char const* comment)
+void cmCustomCommand::SetComment(cm::optional<std::string> comment)
 {
-  this->Comment = comment ? comment : "";
-  this->HaveComment = (comment != nullptr);
+  this->Comment = std::move(comment);
 }
 
 void cmCustomCommand::AppendCommands(cmCustomCommandLines const& commandLines)
diff --git a/Source/cmCustomCommand.h b/Source/cmCustomCommand.h
index 927747e971..0a4a767bee 100644
--- a/Source/cmCustomCommand.h
+++ b/Source/cmCustomCommand.h
@@ -8,6 +8,8 @@
 #include <utility>
 #include <vector>
 
+#include <cm/optional>
+
 #include "cmCustomCommandLines.h"
 #include "cmListFileCache.h"
 #include "cmPolicies.h"
@@ -50,9 +52,9 @@ public:
     return this->WorkingDirectory;
   }
 
-  void SetWorkingDirectory(char const* workingDirectory)
+  void SetWorkingDirectory(std::string const& workingDirectory)
   {
-    this->WorkingDirectory = (workingDirectory ? workingDirectory : "");
+    this->WorkingDirectory = workingDirectory;
   }
 
   /** Get the list of command lines.  */
@@ -60,8 +62,8 @@ public:
   void SetCommandLines(cmCustomCommandLines commandLines);
 
   /** Get the comment string for the command.  */
-  char const* GetComment() const;
-  void SetComment(char const* comment);
+  cm::optional<std::string> const& GetComment() const;
+  void SetComment(cm::optional<std::string> comment);
 
   /** Get a value indicating if the command uses UTF-8 output pipes. */
   bool GetStdPipesUTF8() const { return this->StdPipesUTF8; }
@@ -148,13 +150,12 @@ private:
   cmListFileBacktrace Backtrace;
   cmImplicitDependsList ImplicitDepends;
   std::string Target;
-  std::string Comment;
+  cm::optional<std::string> Comment;
   std::string WorkingDirectory;
   std::string Depfile;
   std::string JobPool;
   std::string Role;
   bool JobserverAware = false;
-  bool HaveComment = false;
   bool EscapeAllowMakeVars = false;
   bool EscapeOldStyle = true;
   bool UsesTerminal = false;
diff --git a/Source/cmCustomCommandGenerator.cxx b/Source/cmCustomCommandGenerator.cxx
index 6bb4b72388..9805ad6c88 100644
--- a/Source/cmCustomCommandGenerator.cxx
+++ b/Source/cmCustomCommandGenerator.cxx
@@ -152,7 +152,7 @@ std::string EvaluateDepfile(std::string const& path,
   return cge->Evaluate(lg, config);
 }
 
-std::string EvaluateComment(char const* comment,
+std::string EvaluateComment(std::string const& comment,
                             cmGeneratorExpression const& ge,
                             cmLocalGenerator* lg, std::string const& config)
 {
@@ -484,12 +484,12 @@ std::string cmCustomCommandGenerator::GetInternalDepfile() const
 
 cm::optional<std::string> cmCustomCommandGenerator::GetComment() const
 {
-  char const* comment = this->CC->GetComment();
-  if (!comment) {
+  if (!this->CC->GetComment()) {
     return cm::nullopt;
   }
-  if (!*comment) {
-    return std::string();
+  std::string const& comment = this->CC->GetComment().value();
+  if (comment.empty()) {
+    return comment;
   }
 
   cmGeneratorExpression ge(*this->LG->GetCMakeInstance(),
diff --git a/Source/cmExecuteProcessCommand.cxx b/Source/cmExecuteProcessCommand.cxx
index 10563d0218..43d4febd33 100644
--- a/Source/cmExecuteProcessCommand.cxx
+++ b/Source/cmExecuteProcessCommand.cxx
@@ -79,7 +79,7 @@ bool cmExecuteProcessCommand(std::vector<std::string> const& args,
 
   struct Arguments : public ArgumentParser::ParseResult
   {
-    std::vector<std::vector<std::string>> Commands;
+    ArgumentParser::MaybeEmpty<std::vector<std::vector<std::string>>> Commands;
     std::string OutputVariable;
     std::string ErrorVariable;
     std::string ResultVariable;
diff --git a/Source/cmExportCommand.cxx b/Source/cmExportCommand.cxx
index 415b5521d5..02f463a331 100644
--- a/Source/cmExportCommand.cxx
+++ b/Source/cmExportCommand.cxx
@@ -487,8 +487,10 @@ static bool HandleSetupMode(std::vector<std::string> const& args,
   {
     ArgumentParser::NonEmpty<std::string> ExportSetName;
     ArgumentParser::NonEmpty<std::string> CxxModulesDirectory;
-    std::vector<std::vector<std::string>> PackageDependencyArgs;
-    std::vector<std::vector<std::string>> TargetArgs;
+    ArgumentParser::MaybeEmpty<std::vector<std::vector<std::string>>>
+      PackageDependencyArgs;
+    ArgumentParser::MaybeEmpty<std::vector<std::vector<std::string>>>
+      TargetArgs;
   };
 
   auto parser = cmArgumentParser<SetupArguments>{};
diff --git a/Source/cmGlobalGenerator.cxx b/Source/cmGlobalGenerator.cxx
index 31ac2d715f..e83d10c093 100644
--- a/Source/cmGlobalGenerator.cxx
+++ b/Source/cmGlobalGenerator.cxx
@@ -3614,7 +3614,7 @@ void ModuleCompilationDatabaseCommandAction::operator()(
 
   cc->SetBacktrace(lfbt);
   cc->SetCommandLines(command_lines);
-  cc->SetWorkingDirectory(lg.GetBinaryDirectory().c_str());
+  cc->SetWorkingDirectory(lg.GetBinaryDirectory());
   cc->SetDependsExplicitOnly(true);
   cc->SetOutputs(this->Output);
   if (!inputs.empty()) {
@@ -3646,7 +3646,7 @@ void ModuleCompilationDatabaseTargetAction::operator()(
   std::unique_ptr<cmCustomCommand> cc)
 {
   cc->SetBacktrace(lfbt);
-  cc->SetWorkingDirectory(lg.GetBinaryDirectory().c_str());
+  cc->SetWorkingDirectory(lg.GetBinaryDirectory());
   std::vector<std::string> target_inputs;
   target_inputs.emplace_back(this->Output);
   cc->SetDepends(target_inputs);
@@ -3698,7 +3698,7 @@ bool cmGlobalGenerator::AddBuildDatabaseTargets()
 
   static cm::static_string_view TargetPrefix = "cmake_build_database"_s;
   auto AddMergeTarget =
-    [&mf](std::string const& name, char const* comment,
+    [&mf](std::string const& name, std::string const& comment,
           std::string const& output,
           std::function<std::vector<std::string>()> inputs) {
       // Add the custom command.
@@ -3732,13 +3732,13 @@ bool cmGlobalGenerator::AddBuildDatabaseTargets()
                              lang, ".json");
       mf->GetOrCreateGeneratedSource(output);
       AddMergeTarget(
-        cmStrCat(TargetPrefix, '-', lang), comment.c_str(), output,
+        cmStrCat(TargetPrefix, '-', lang), comment, output,
         [this, lang]() { return this->PerLanguageModuleDbs[lang]; });
       all_lang_paths.emplace_back(std::move(output));
     }
 
     // Add the overall target.
-    auto const* comment = "Combining module command databases";
+    std::string comment{ "Combining module command databases" };
     auto output =
       cmStrCat(mf->GetHomeOutputDirectory(), "/build_database.json");
     mf->GetOrCreateGeneratedSource(output);
@@ -3758,8 +3758,8 @@ bool cmGlobalGenerator::AddBuildDatabaseTargets()
       auto output = cmStrCat(mf->GetHomeOutputDirectory(), "/build_database_",
                              lang, '_', config, ".json");
       mf->GetOrCreateGeneratedSource(output);
-      AddMergeTarget(cmStrCat(TargetPrefix, '-', lang, '-', config),
-                     comment.c_str(), output, [this, config, lang]() {
+      AddMergeTarget(cmStrCat(TargetPrefix, '-', lang, '-', config), comment,
+                     output, [this, config, lang]() {
                        return this->PerConfigModuleDbs[config][lang];
                      });
       all_config_paths.emplace_back(std::move(output));
@@ -3770,8 +3770,8 @@ bool cmGlobalGenerator::AddBuildDatabaseTargets()
     auto output = cmStrCat(mf->GetHomeOutputDirectory(), "/build_database_",
                            config, ".json");
     mf->GetOrCreateGeneratedSource(output);
-    AddMergeTarget(cmStrCat(TargetPrefix, '-', config), comment.c_str(),
-                   output, [all_config_paths]() { return all_config_paths; });
+    AddMergeTarget(cmStrCat(TargetPrefix, '-', config), comment, output,
+                   [all_config_paths]() { return all_config_paths; });
   }
 
   // NMC considerations
@@ -3783,13 +3783,13 @@ bool cmGlobalGenerator::AddBuildDatabaseTargets()
                            lang, ".json");
     mf->GetOrCreateGeneratedSource(output);
     AddMergeTarget(
-      cmStrCat(TargetPrefix, '-', lang), comment.c_str(), output,
+      cmStrCat(TargetPrefix, '-', lang), comment, output,
       [this, lang]() { return this->PerLanguageModuleDbs[lang]; });
     all_config_paths.emplace_back(std::move(output));
   }
 
   // Add the overall target.
-  auto const* comment = "Combining all module command databases";
+  std::string comment{ "Combining all module command databases" };
   auto output = cmStrCat(mf->GetHomeOutputDirectory(), "/build_database.json");
   mf->GetOrCreateGeneratedSource(output);
   AddMergeTarget(std::string(TargetPrefix), comment, output,
@@ -3844,7 +3844,7 @@ void cmGlobalGenerator::CreateGlobalTarget(GlobalTargetInfo const& gti,
   // Store the custom command in the target.
   cmCustomCommand cc;
   cc.SetCommandLines(gti.CommandLines);
-  cc.SetWorkingDirectory(gti.WorkingDir.c_str());
+  cc.SetWorkingDirectory(gti.WorkingDir);
   cc.SetStdPipesUTF8(gti.StdPipesUTF8);
   cc.SetUsesTerminal(gti.UsesTerminal);
   cc.SetRole(gti.Role);
diff --git a/Source/cmGlobalGhsMultiGenerator.cxx b/Source/cmGlobalGhsMultiGenerator.cxx
index fe3f041337..d93d345445 100644
--- a/Source/cmGlobalGhsMultiGenerator.cxx
+++ b/Source/cmGlobalGhsMultiGenerator.cxx
@@ -9,6 +9,7 @@
 #include <utility>
 
 #include <cm/memory>
+#include <cm/optional>
 #include <cm/string>
 #include <cm/string_view>
 #include <cmext/algorithm>
diff --git a/Source/cmGlobalXCodeGenerator.cxx b/Source/cmGlobalXCodeGenerator.cxx
index 78d9cb1045..696a3e3ccb 100644
--- a/Source/cmGlobalXCodeGenerator.cxx
+++ b/Source/cmGlobalXCodeGenerator.cxx
@@ -829,7 +829,7 @@ void cmGlobalXCodeGenerator::AddExtraTargets(
         cc = cm::make_unique<cmCustomCommand>();
         cc->SetCommandLines(legacyDependHelperCommandLines);
         cc->SetComment("Depend check for xcode");
-        cc->SetWorkingDirectory(legacyDependHelperDir.c_str());
+        cc->SetWorkingDirectory(legacyDependHelperDir);
         gen->AddCustomCommandToTarget(
           target->GetName(), cmCustomCommandType::POST_BUILD, std::move(cc),
           cmObjectLibraryCommands::Accept);
diff --git a/Source/cmInstallCommand.cxx b/Source/cmInstallCommand.cxx
index 89167ab544..33721d57d6 100644
--- a/Source/cmInstallCommand.cxx
+++ b/Source/cmInstallCommand.cxx
@@ -1016,7 +1016,7 @@ bool HandleTargetsMode(std::vector<std::string> const& args,
     ArgumentParser::MaybeEmpty<std::vector<std::string>> PublicHeader;
     ArgumentParser::MaybeEmpty<std::vector<std::string>> Resource;
     ArgumentParser::MaybeEmpty<std::vector<std::string>> CxxModulesBmi;
-    std::vector<std::vector<std::string>> FileSets;
+    ArgumentParser::MaybeEmpty<std::vector<std::vector<std::string>>> FileSets;
   };
 
   static auto const argHelper =
diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index cfb5d27090..3c06484fa1 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -3069,7 +3069,7 @@ void cmLocalGenerator::CopyPchCompilePdb(
 
   auto cc = cm::make_unique<cmCustomCommand>();
   cc->SetCommandLines(commandLines);
-  cc->SetComment(comment.c_str());
+  cc->SetComment(comment);
   cc->SetStdPipesUTF8(true);
   cc->AppendDepends(
     { reuseTarget->GetPchFile(config, language), copy_script });
diff --git a/Source/cmLocalVisualStudio7Generator.cxx b/Source/cmLocalVisualStudio7Generator.cxx
index acc3ba6b78..d9a7cf77c6 100644
--- a/Source/cmLocalVisualStudio7Generator.cxx
+++ b/Source/cmLocalVisualStudio7Generator.cxx
@@ -272,7 +272,7 @@ cmSourceFile* cmLocalVisualStudio7Generator::CreateVCProjBuildRule()
   cc->SetMainDependency(makefileIn);
   cc->SetDepends(listFiles);
   cc->SetCommandLines(commandLines);
-  cc->SetComment(comment.c_str());
+  cc->SetComment(comment);
   cc->SetEscapeOldStyle(false);
   cc->SetStdPipesUTF8(true);
   cc->SetUsesTerminal(true);
diff --git a/Source/cmNinjaNormalTargetGenerator.cxx b/Source/cmNinjaNormalTargetGenerator.cxx
index 53f8902e30..8a569188a3 100644
--- a/Source/cmNinjaNormalTargetGenerator.cxx
+++ b/Source/cmNinjaNormalTargetGenerator.cxx
@@ -1520,7 +1520,7 @@ void cmNinjaNormalTargetGenerator::WriteLinkStatement(
                                      true, config);
         localGen.AppendCustomCommandLines(ccg, *cmdLineLists[i]);
         if (cc.GetComment()) {
-          auto cge = ge.Parse(cc.GetComment());
+          auto cge = ge.Parse(cc.GetComment().value());
           cmdComments[i]->emplace_back(
             cge->Evaluate(this->GetLocalGenerator(), config));
         }
diff --git a/Source/cmNinjaUtilityTargetGenerator.cxx b/Source/cmNinjaUtilityTargetGenerator.cxx
index 08d6019d12..e4f3b270a2 100644
--- a/Source/cmNinjaUtilityTargetGenerator.cxx
+++ b/Source/cmNinjaUtilityTargetGenerator.cxx
@@ -11,6 +11,8 @@
 #include <utility>
 #include <vector>
 
+#include <cm/optional>
+
 #include "cmCustomCommand.h"
 #include "cmCustomCommandGenerator.h"
 #include "cmGeneratedFileStream.h"
@@ -96,7 +98,7 @@ void cmNinjaUtilityTargetGenerator::WriteUtilBuildStatements(
           if (!commandDesc.empty()) {
             commandDesc += "; ";
           }
-          auto cge = ge.Parse(ci.GetComment());
+          auto cge = ge.Parse(ci.GetComment().value());
           commandDesc += cge->Evaluate(this->GetLocalGenerator(), config);
         }
         util_outputs.Add(ccg.GetByproducts());
diff --git a/Source/cmPlaceholderExpander.cxx b/Source/cmPlaceholderExpander.cxx
index aea427b681..54b0686d97 100644
--- a/Source/cmPlaceholderExpander.cxx
+++ b/Source/cmPlaceholderExpander.cxx
@@ -4,7 +4,8 @@
 
 #include "cmsys/String.h"
 
-std::string& cmPlaceholderExpander::ExpandVariables(std::string& s)
+std::string& cmPlaceholderExpander::ExpandVariables(std::string& s,
+                                                    HandleGenex handleGenex)
 {
   std::string::size_type start = s.find('<');
   // no variables to expand
@@ -14,6 +15,13 @@ std::string& cmPlaceholderExpander::ExpandVariables(std::string& s)
   std::string::size_type pos = 0;
   std::string expandedInput;
   while (start != std::string::npos && start < s.size() - 2) {
+    if (handleGenex == HandleGenex::Yes && start != 0 && s[start - 1] == '$') {
+      // this is a generator expression
+      // skip it and try to find the next < in the string
+      start = s.find('<', start + 1);
+      continue;
+    }
+
     std::string::size_type end = s.find('>', start);
     // if we find a < with no > we are done
     if (end == std::string::npos) {
diff --git a/Source/cmPlaceholderExpander.h b/Source/cmPlaceholderExpander.h
index 3a4b1bc376..7c54ef60a1 100644
--- a/Source/cmPlaceholderExpander.h
+++ b/Source/cmPlaceholderExpander.h
@@ -10,9 +10,16 @@
 class cmPlaceholderExpander
 {
 public:
+  enum class HandleGenex
+  {
+    No,
+    Yes
+  };
+
   virtual ~cmPlaceholderExpander() = default;
 
-  std::string& ExpandVariables(std::string& string);
+  std::string& ExpandVariables(std::string& string,
+                               HandleGenex handleGenex = HandleGenex::No);
 
 protected:
   virtual std::string ExpandVariable(std::string const& variable) = 0;
diff --git a/Source/cmQTWrapCPPCommand.cxx b/Source/cmQTWrapCPPCommand.cxx
index d1dcb7619b..26dafebd0a 100644
--- a/Source/cmQTWrapCPPCommand.cxx
+++ b/Source/cmQTWrapCPPCommand.cxx
@@ -5,6 +5,7 @@
 #include <utility>
 
 #include <cm/memory>
+#include <cm/optional>
 #include <cm/string_view>
 
 #include "cmCustomCommand.h"
diff --git a/Source/cmQtAutoGenGlobalInitializer.cxx b/Source/cmQtAutoGenGlobalInitializer.cxx
index a992123ad3..b9172befe9 100644
--- a/Source/cmQtAutoGenGlobalInitializer.cxx
+++ b/Source/cmQtAutoGenGlobalInitializer.cxx
@@ -6,6 +6,7 @@
 #include <utility>
 
 #include <cm/memory>
+#include <cm/optional>
 
 #include "cmCustomCommand.h"
 #include "cmDiagnostics.h"
@@ -171,9 +172,9 @@ void cmQtAutoGenGlobalInitializer::GetOrCreateGlobalTarget(
 
     // Create utility target
     auto cc = cm::make_unique<cmCustomCommand>();
-    cc->SetWorkingDirectory(makefile->GetHomeOutputDirectory().c_str());
+    cc->SetWorkingDirectory(makefile->GetHomeOutputDirectory());
     cc->SetEscapeOldStyle(false);
-    cc->SetComment(comment.c_str());
+    cc->SetComment(comment);
     cmTarget* target = localGen->AddUtilityCommand(name, true, std::move(cc));
     localGen->AddGeneratorTarget(
       cm::make_unique<cmGeneratorTarget>(target, localGen));
diff --git a/Source/cmQtAutoGenInitializer.cxx b/Source/cmQtAutoGenInitializer.cxx
index e24bd38735..afd68328a2 100644
--- a/Source/cmQtAutoGenInitializer.cxx
+++ b/Source/cmQtAutoGenInitializer.cxx
@@ -19,6 +19,7 @@
 #include <cm/algorithm>
 #include <cm/iterator>
 #include <cm/memory>
+#include <cm/optional>
 #include <cm/string_view>
 #include <cmext/algorithm>
 #include <cmext/string_view>
@@ -1593,7 +1594,7 @@ bool cmQtAutoGenInitializer::InitAutogenTarget()
       cc->SetOutputs(timestampFileGenex);
       cc->SetDepends(uicDependencies);
       cc->SetComment("");
-      cc->SetWorkingDirectory(this->Dir.Work.c_str());
+      cc->SetWorkingDirectory(this->Dir.Work);
       cc->SetEscapeOldStyle(false);
       cc->SetStdPipesUTF8(stdPipesUTF8);
       this->LocalGen->AddCustomCommandToOutput(std::move(cc));
@@ -1607,9 +1608,9 @@ bool cmQtAutoGenInitializer::InitAutogenTarget()
     cmCustomCommand cc;
     cc.SetByproducts(autogenByproducts);
     cc.SetCommandLines(commandLines);
-    cc.SetComment(autogenComment.c_str());
+    cc.SetComment(autogenComment);
     cc.SetBacktrace(this->Makefile->GetBacktrace());
-    cc.SetWorkingDirectory(this->Dir.Work.c_str());
+    cc.SetWorkingDirectory(this->Dir.Work);
     cc.SetStdPipesUTF8(stdPipesUTF8);
     cc.SetEscapeOldStyle(false);
     cc.SetEscapeAllowMakeVars(true);
@@ -1671,7 +1672,7 @@ bool cmQtAutoGenInitializer::InitAutogenTarget()
           cmStrCat(this->GenTarget->GetName(), "_autogen_timestamp_deps");
 
         auto cc = cm::make_unique<cmCustomCommand>();
-        cc->SetWorkingDirectory(this->Dir.Work.c_str());
+        cc->SetWorkingDirectory(this->Dir.Work);
         cc->SetDepends(dependencies);
         cc->SetEscapeOldStyle(false);
         timestampTarget = this->LocalGen->AddUtilityCommand(
@@ -1742,8 +1743,8 @@ bool cmQtAutoGenInitializer::InitAutogenTarget()
       cc->SetByproducts(timestampByproducts);
       cc->SetDepends(dependencies);
       cc->SetCommandLines(commandLines);
-      cc->SetComment(autogenComment.c_str());
-      cc->SetWorkingDirectory(this->Dir.Work.c_str());
+      cc->SetComment(autogenComment);
+      cc->SetWorkingDirectory(this->Dir.Work);
       cc->SetEscapeOldStyle(false);
       cc->SetDepfile(depFile);
       cc->SetStdPipesUTF8(stdPipesUTF8);
@@ -1763,12 +1764,12 @@ bool cmQtAutoGenInitializer::InitAutogenTarget()
     } else {
       // Create autogen target
       auto cc = cm::make_unique<cmCustomCommand>();
-      cc->SetWorkingDirectory(this->Dir.Work.c_str());
+      cc->SetWorkingDirectory(this->Dir.Work);
       cc->SetByproducts(autogenByproducts);
       cc->SetDepends(dependencies);
       cc->SetCommandLines(commandLines);
       cc->SetEscapeOldStyle(false);
-      cc->SetComment(autogenComment.c_str());
+      cc->SetComment(autogenComment);
       cmTarget* autogenTarget = this->LocalGen->AddUtilityCommand(
         this->AutogenTarget.Name, true, std::move(cc));
       // Create autogen generator target
@@ -1878,9 +1879,9 @@ bool cmQtAutoGenInitializer::InitRccTargets()
                FileProjectRelativePath(this->Makefile, qrc.QrcFile));
 
     auto cc = cm::make_unique<cmCustomCommand>();
-    cc->SetWorkingDirectory(this->Dir.Work.c_str());
+    cc->SetWorkingDirectory(this->Dir.Work);
     cc->SetCommandLines(commandLines);
-    cc->SetComment(ccComment.c_str());
+    cc->SetComment(ccComment);
     cc->SetStdPipesUTF8(true);
 
     if (qrc.Generated || this->Rcc.GlobalTarget) {
diff --git a/Source/cmSourceFile.cxx b/Source/cmSourceFile.cxx
index 6ee095af83..04220e3a3b 100644
--- a/Source/cmSourceFile.cxx
+++ b/Source/cmSourceFile.cxx
@@ -49,8 +49,6 @@ std::string const& cmSourceFile::GetExtension() const
   return this->Extension;
 }
 
-std::string const propTRUE = "1";
-std::string const propFALSE = "0";
 std::string const cmSourceFile::propLANGUAGE = "LANGUAGE";
 std::string const cmSourceFile::propLOCATION = "LOCATION";
 std::string const cmSourceFile::propGENERATED = "GENERATED";
@@ -387,9 +385,9 @@ cmValue cmSourceFile::GetPropertyForUser(std::string const& prop)
       (cmp0118 != cmPolicies::OLD && cmp0118 != cmPolicies::WARN);
     if (this->GetIsGenerated((!cmp0118new) ? CheckScope::GlobalAndLocal
                                            : CheckScope::Global)) {
-      return cmValue(propTRUE);
+      return cmValue::True;
     }
-    return cmValue(propFALSE);
+    return cmValue::False;
   }
 
   // Perform the normal property lookup.
diff --git a/Source/cmSourceFilePropertyHelper.cxx b/Source/cmSourceFilePropertyHelper.cxx
index 0df2d8bf74..1c33f4f662 100644
--- a/Source/cmSourceFilePropertyHelper.cxx
+++ b/Source/cmSourceFilePropertyHelper.cxx
@@ -14,9 +14,9 @@
 #include "cmSystemTools.h"
 #include "cmValue.h"
 
-static bool GetSourceFilePropertyGENERATED(std::string const& name,
-                                           cmMakefile& mf,
-                                           cmValue& propertyValue)
+namespace {
+bool GetSourceFilePropertyGENERATED(std::string const& name, cmMakefile& mf,
+                                    cmValue& propertyValue)
 {
   // Globally set as generated?
   // Note: If the given "name" only contains a filename or a relative path
@@ -26,13 +26,11 @@ static bool GetSourceFilePropertyGENERATED(std::string const& name,
   //       generated in the build-directory. Therefore, we first check for
   //       a generated file in the build-directory before we check for a
   //       generated file in the source-directory.
-  static std::string const sOne = "1";
-  static std::string const sZero = "0";
   {
     auto file =
       cmSystemTools::CollapseFullPath(name, mf.GetCurrentBinaryDirectory());
     if (mf.GetGlobalGenerator()->IsGeneratedFile(file)) {
-      propertyValue = cmValue(sOne);
+      propertyValue = cmValue::True;
       return true;
     }
   }
@@ -40,13 +38,14 @@ static bool GetSourceFilePropertyGENERATED(std::string const& name,
     auto file =
       cmSystemTools::CollapseFullPath(name, mf.GetCurrentSourceDirectory());
     if (mf.GetGlobalGenerator()->IsGeneratedFile(file)) {
-      propertyValue = cmValue(sOne);
+      propertyValue = cmValue::True;
       return true;
     }
   }
-  propertyValue = cmValue(sZero);
+  propertyValue = cmValue::False;
   return true;
 }
+}
 
 cmGetSourceFilePropertyResult cmGetSourceFileProperty(
   std::string const& sourceName, std::string const& propertyName,
diff --git a/Source/cmTargetSourcesCommand.cxx b/Source/cmTargetSourcesCommand.cxx
index 146262438e..5d178268c7 100644
--- a/Source/cmTargetSourcesCommand.cxx
+++ b/Source/cmTargetSourcesCommand.cxx
@@ -42,7 +42,7 @@ auto const FileSetArgsParser = cmArgumentParser<FileSetArgs>()
 
 struct FileSetsArgs
 {
-  std::vector<std::vector<std::string>> FileSets;
+  ArgumentParser::MaybeEmpty<std::vector<std::vector<std::string>>> FileSets;
 };
 
 auto const FileSetsArgsParser =
diff --git a/Source/cmValue.cxx b/Source/cmValue.cxx
index 83d18b32c5..bc40371973 100644
--- a/Source/cmValue.cxx
+++ b/Source/cmValue.cxx
@@ -8,6 +8,14 @@
 
 #include "cmStringAlgorithms.h"
 
+namespace {
+std::string True{ "1" };
+std::string False{ "0" };
+}
+
+cmValue cmValue::True{ ::True };
+cmValue cmValue::False{ ::False };
+
 std::string cmValue::Empty;
 
 bool cmValue::IsOn(cm::string_view value) noexcept
diff --git a/Source/cmValue.h b/Source/cmValue.h
index 9151a29222..58edd54b31 100644
--- a/Source/cmValue.h
+++ b/Source/cmValue.h
@@ -13,6 +13,9 @@
 class cmValue
 {
 public:
+  static cmValue True;
+  static cmValue False;
+
   cmValue() noexcept = default;
   cmValue(std::nullptr_t) noexcept {}
   explicit cmValue(std::string const* value) noexcept
diff --git a/Tests/CMakeLib/testArgumentParser.cxx b/Tests/CMakeLib/testArgumentParser.cxx
index 176211de55..7d714746cd 100644
--- a/Tests/CMakeLib/testArgumentParser.cxx
+++ b/Tests/CMakeLib/testArgumentParser.cxx
@@ -45,10 +45,14 @@ struct Result : ArgumentParser::ParseResult
   cm::optional<ArgumentParser::NonEmpty<std::vector<std::string>>> List5;
   cm::optional<ArgumentParser::MaybeEmpty<std::vector<std::string>>> List6;
 
-  std::vector<std::vector<std::string>> Multi1;
-  std::vector<std::vector<std::string>> Multi2;
-  cm::optional<std::vector<std::vector<std::string>>> Multi3;
-  cm::optional<std::vector<std::vector<std::string>>> Multi4;
+  ArgumentParser::MaybeEmpty<std::vector<std::vector<std::string>>> Multi1;
+  ArgumentParser::MaybeEmpty<std::vector<std::vector<std::string>>> Multi2;
+  cm::optional<
+    ArgumentParser::MaybeEmpty<std::vector<std::vector<std::string>>>>
+    Multi3;
+  cm::optional<
+    ArgumentParser::MaybeEmpty<std::vector<std::vector<std::string>>>>
+    Multi4;
 
   cm::optional<std::string> Pos0;
   cm::optional<std::string> Pos1;