cmCustomCommandGenerator: refactor GetComment to return std::string

Refactoring was done because EvaluateComment leaked memory.

Source/cmCustomCommandGenerator.cxx

@@ -463,9 +463,12 @@ std::string cmCustomCommandGenerator::GetInternalDepfile() const
   return this->ComputeInternalDepfile(this->OutputConfig, depfile);
 }
 
-const char* cmCustomCommandGenerator::GetComment() const
+cm::optional<std::string> cmCustomCommandGenerator::GetComment() const
 {
-  return this->CC->GetComment();
+  if (const char* comment = this->CC->GetComment()) {
+    return comment;
+  }
+  return cm::nullopt;
 }
 
 std::string cmCustomCommandGenerator::GetWorkingDirectory() const

Source/cmCustomCommandGenerator.h

@@ -58,7 +58,7 @@ public:
   unsigned int GetNumberOfCommands() const;
   std::string GetCommand(unsigned int c) const;
   void AppendArguments(unsigned int c, std::string& cmd) const;
-  const char* GetComment() const;
+  cm::optional<std::string> GetComment() const;
   std::string GetWorkingDirectory() const;
   std::vector<std::string> const& GetOutputs() const;
   std::vector<std::string> const& GetByproducts() const;

Source/cmGhsMultiTargetGenerator.cxx

@@ -9,6 +9,8 @@
 #include <utility>
 #include <vector>
 
+#include <cm/optional>
+
 #include "cmCustomCommand.h"
 #include "cmCustomCommandGenerator.h"
 #include "cmGeneratedFileStream.h"
@@ -411,9 +413,8 @@ void cmGhsMultiTargetGenerator::WriteCustomCommandsHelper(
   cmdLines.push_back("@echo off");
 #endif
   // Echo the custom command's comment text.
-  const char* comment = ccg.GetComment();
-  if (comment && *comment) {
-    std::string echocmd = cmStrCat("echo ", comment);
+  if (cm::optional<std::string> comment = ccg.GetComment()) {
+    std::string echocmd = cmStrCat("echo ", *comment);
     cmdLines.push_back(std::move(echocmd));
   }
 

Source/cmGlobalXCodeGenerator.cxx

@@ -13,6 +13,7 @@
 #include <utility>
 
 #include <cm/memory>
+#include <cm/optional>
 #include <cmext/algorithm>
 #include <cmext/string_view>
 
@@ -2280,11 +2281,11 @@ void cmGlobalXCodeGenerator::CreateCustomRulesMakefile(
       }
       makefileStream << "\n";
 
-      if (const char* comment = ccg.GetComment()) {
+      if (cm::optional<std::string> comment = ccg.GetComment()) {
         std::string echo_cmd =
           cmStrCat("echo ",
                    (this->CurrentLocalGenerator->EscapeForShell(
-                     comment, ccg.GetCC().GetEscapeAllowMakeVars())));
+                     *comment, ccg.GetCC().GetEscapeAllowMakeVars())));
         makefileStream << "\t" << echo_cmd << "\n";
       }
 

Source/cmLocalGenerator.cxx

@@ -3484,8 +3484,8 @@ std::string cmLocalGenerator::ConstructComment(
   cmCustomCommandGenerator const& ccg, const char* default_comment) const
 {
   // Check for a comment provided with the command.
-  if (ccg.GetComment()) {
-    return ccg.GetComment();
+  if (cm::optional<std::string> comment = ccg.GetComment()) {
+    return *comment;
   }
 
   // Construct a reasonable default comment if possible.

Source/cmLocalUnixMakefileGenerator3.cxx

@@ -10,6 +10,7 @@
 #include <utility>
 
 #include <cm/memory>
+#include <cm/optional>
 #include <cm/string_view>
 #include <cm/vector>
 #include <cmext/algorithm>
@@ -945,9 +946,8 @@ void cmLocalUnixMakefileGenerator3::AppendCustomCommand(
   // post-build command comments.  Custom build step commands have
   // their comments generated elsewhere.
   if (echo_comment) {
-    const char* comment = ccg.GetComment();
-    if (comment && *comment) {
-      this->AppendEcho(commands, comment,
+    if (cm::optional<std::string> comment = ccg.GetComment()) {
+      this->AppendEcho(commands, *comment,
                        cmLocalUnixMakefileGenerator3::EchoGenerate);
     }
   }

Source/cmLocalVisualStudio7Generator.cxx

@@ -10,6 +10,7 @@
 #include <utility>
 
 #include <cm/memory>
+#include <cm/optional>
 #include <cmext/algorithm>
 
 #include <windows.h>
@@ -592,9 +593,8 @@ public:
   {
     cmCustomCommandGenerator ccg(cc, this->Config, this->LG);
     if (this->First) {
-      const char* comment = ccg.GetComment();
-      if (comment && *comment) {
-        this->Stream << "\nDescription=\"" << this->LG->EscapeForXML(comment)
+      if (cm::optional<std::string> comment = ccg.GetComment()) {
+        this->Stream << "\nDescription=\"" << this->LG->EscapeForXML(*comment)
                      << "\"";
       }
       this->Stream << "\nCommandLine=\"";