ENH: Simplify string attributes in Xcode generator

This change cleans up the implementation of cmXCodeObject to avoid
un-escaping and re-escaping string values.  There is no need to store
the string in escaped form.  It can be escaped once when it is printed
out to the generated project file.

Source/cmGlobalXCodeGenerator.cxx

@@ -689,7 +689,7 @@ cmGlobalXCodeGenerator::CreateXCodeTargets(cmLocalGenerator* gen,
       cmTarget::SourceFileFlags tsFlags =
         cmtarget.GetTargetSourceFileFlags(*i);
 
-      if(strcmp(filetype->GetString(), "\"compiled.mach-o.objfile\"") == 0)
+      if(strcmp(filetype->GetString(), "compiled.mach-o.objfile") == 0)
         {
         externalObjFiles.push_back(xsf);
         }
@@ -1957,22 +1957,8 @@ void cmGlobalXCodeGenerator::AppendOrAddBuildSetting(cmXCodeObject* settings,
     else
       {
       std::string oldValue = attr->GetString();
-
-      // unescape escaped quotes internal to the string:
-      cmSystemTools::ReplaceString(oldValue, "\\\"", "\"");
-
-      // remove surrounding quotes, if any:
-      std::string::size_type len = oldValue.length();
-      if(oldValue[0] == '\"' && oldValue[len-1] == '\"')
-        {
-        oldValue = oldValue.substr(1, len-2);
-        }
-
       oldValue += " ";
       oldValue += value;
-
-      // SetString automatically escapes internal quotes and then surrounds
-      // the result with quotes if necessary...
       attr->SetString(oldValue.c_str());
       }
     }

Source/cmXCodeObject.cxx

@@ -151,7 +151,9 @@ void cmXCodeObject::Print(std::ostream& out)
 
         if(j->second->TypeValue == STRING)
           {
-          out << j->first << " = " << j->second->String << ";";
+          out << j->first << " = ";
+          j->second->PrintString(out);
+          out << ";";
           }
         else if(j->second->TypeValue == OBJECT_LIST)
           {
@@ -160,7 +162,8 @@ void cmXCodeObject::Print(std::ostream& out)
             {
             if(j->second->List[k]->TypeValue == STRING)
               {
-              out << j->second->List[k]->String << ", ";
+              j->second->List[k]->PrintString(out);
+              out << ", ";
               }
             else
               {
@@ -192,7 +195,9 @@ void cmXCodeObject::Print(std::ostream& out)
       }
     else if(object->TypeValue == STRING)
       {
-      out << i->first << " = " << object->String << ";" << separator;
+      out << i->first << " = ";
+      object->PrintString(out);
+      out << ";" << separator;
       }
     else
       {
@@ -230,29 +235,32 @@ void cmXCodeObject::CopyAttributes(cmXCodeObject* copy)
 }
 
 //----------------------------------------------------------------------------
-void cmXCodeObject::SetString(const char* s)
+void cmXCodeObject::PrintString(std::ostream& os) const
 {
-  std::string ss = s;
-  if(ss.size() == 0)
-    {
-    this->String = "\"\"";
-    return;
-    }
-  // escape quotes
-  cmSystemTools::ReplaceString(ss, "\"", "\\\"");
-  bool needQuote = false;
-  this->String = "";
-  if(ss.find_first_of(" <>.+-=@") != ss.npos)
-    {
-    needQuote = true;
-    }
-  if(needQuote)
-    {
-    this->String = "\"";
-    }
-  this->String += ss;
-  if(needQuote)
+  // The string needs to be quoted if it contains any characters
+  // considered special by the Xcode project file parser.
+  bool needQuote =
+    (this->String.empty() ||
+     this->String.find_first_of(" <>.+-=@") != this->String.npos);
+  const char* quote = needQuote? "\"" : "";
+
+  // Print the string, quoted and escaped as necessary.
+  os << quote;
+  for(std::string::const_iterator i = this->String.begin();
+      i != this->String.end(); ++i)
     {
-    this->String += "\"";
+    if(*i == '"')
+      {
+      // Escape double-quotes.
+      os << '\\';
+      }
+    os << *i;
     }
+  os << quote;
+}
+
+//----------------------------------------------------------------------------
+void cmXCodeObject::SetString(const char* s)
+{
+  this->String = s;
 }

Source/cmXCodeObject.h

@@ -147,6 +147,8 @@ public:
   std::vector<cmXCodeObject*> const& GetObjectList() { return this->List;}
   void SetComment(const char* c) { this->Comment = c;}
 protected:
+  void PrintString(std::ostream& os) const;
+
   cmTarget* Target;
   Type TypeValue;
   cmStdString Id;