add an EMPTY_OUSTRING in OUString header

we already declare the same thing in various places,
and I intend to be using this some more, so it makes
sense to only declare it in one place

Change-Id: Ifea6b589e992dd9f6cd8f2301f837e71397481c8
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/176046
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

include/rtl/ustring.hxx

@@ -3987,6 +3987,16 @@ struct hash<::rtl::OUString>
 
 }
 
+#if !(defined _MSC_VER && _MSC_VER <= 1929 && defined _MANAGED)
+/**
+  * static empty string object, handy for returning from functions where the function is
+  * returning a "const OUString &"
+  *
+  * @since LibreOffice 25.2
+  */
+static inline constexpr ::rtl::OUString EMPTY_OUSTRING = u""_ustr;
+#endif
+
 #endif
 /// @endcond
 

include/xmloff/maptype.hxx

@@ -99,8 +99,6 @@ struct XMLPropertyMapEntry
      */
     bool            mbImportOnly;
 
-    static constexpr OUString EMPTY{u""_ustr};
-
     constexpr XMLPropertyMapEntry(
             const OUString& sApiName,
             sal_uInt16      nNameSpace,
@@ -119,7 +117,7 @@ struct XMLPropertyMapEntry
     /// used to mark the end of the array
     constexpr XMLPropertyMapEntry(std::nullptr_t)
         :
-        msApiName(EMPTY),
+        msApiName(EMPTY_OUSTRING),
         meXMLName(xmloff::token::XML_TOKEN_INVALID), mnNameSpace(0), mnType(0),
         mnContextId(0), mnEarliestODFVersionForExport(SvtSaveOptions::ODFSVER_010),
         mbImportOnly(false)

svx/source/customshapes/EnhancedCustomShapeTypeNames.cxx

@@ -539,12 +539,11 @@ static const TypeACCNameHashMap& GetACCHashMap()
 
 const OUString & EnhancedCustomShapeTypeNames::GetAccName( const OUString& rShapeType )
 {
-    static const OUString EMPTY;
     const TypeACCNameHashMap& rACCMap = GetACCHashMap();
     auto aHashIter = rACCMap.find( rShapeType );
     if ( aHashIter != rACCMap.end() )
         return aHashIter->second;
-    return EMPTY;
+    return EMPTY_OUSTRING;
 }
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */

svx/source/svdraw/svdobj.cxx

@@ -724,14 +724,12 @@ void SdrObject::SetName(const OUString& rStr, const bool bSetChanged)
 
 const OUString & SdrObject::GetName() const
 {
-    static constexpr OUString EMPTY = u""_ustr;
-
     if(m_pPlusData)
     {
         return m_pPlusData->aObjName;
     }
 
-    return EMPTY;
+    return EMPTY_OUSTRING;
 }
 
 void SdrObject::SetTitle(const OUString& rStr)

svx/source/tbxctrls/grafctrl.cxx

@@ -160,7 +160,6 @@ struct CommandToRID
 
 static OUString ImplGetRID( std::u16string_view aCommand )
 {
-    static constexpr OUString EMPTY = u""_ustr;
     static constexpr CommandToRID aImplCommandToResMap[] =
     {
         { ".uno:GrafRed",           RID_SVXBMP_GRAF_RED             },
@@ -170,7 +169,7 @@ static OUString ImplGetRID( std::u16string_view aCommand )
         { ".uno:GrafContrast",      RID_SVXBMP_GRAF_CONTRAST        },
         { ".uno:GrafGamma",         RID_SVXBMP_GRAF_GAMMA           },
         { ".uno:GrafTransparence",  RID_SVXBMP_GRAF_TRANSPARENCE    },
-        { nullptr, EMPTY }
+        { nullptr, EMPTY_OUSTRING }
     };
 
     OUString sRID;

sw/source/uibase/app/docstyle.cxx

@@ -858,8 +858,7 @@ const OUString&  SwDocStyleSheet::GetParent() const
         case SfxStyleFamily::Pseudo:
         default:
             {
-                static const OUString sEmpty;
-                return sEmpty; // there's no parent
+                return EMPTY_OUSTRING; // there's no parent
             }
         }
 

unotools/source/i18n/localedatawrapper.cxx

@@ -382,8 +382,7 @@ const OUString& LocaleDataWrapper::getOneReservedWord( sal_Int16 nWord ) const
     if ( nWord < 0 || o3tl::make_unsigned(nWord) >= aReservedWords.size() )
     {
         SAL_WARN( "unotools.i18n", "getOneReservedWord: bounds" );
-        static const OUString EMPTY;
-        return EMPTY;
+        return EMPTY_OUSTRING;
     }
     return aReservedWords[nWord];
 }

xmloff/source/core/unointerfacetouniqueidentifiermapper.cxx

@@ -112,8 +112,7 @@ const OUString& UnoInterfaceToUniqueIdentifierMapper::getIdentifier( const Refer
     }
     else
     {
-        static const OUString aEmpty;
-        return aEmpty;
+        return EMPTY_OUSTRING;
     }
 }