Turn OUStringLiteral into a consteval'ed, static-refcound rtl_uString

...from which an OUString can cheaply be instantiated.  This is the OUString
equivalent of 4b9e440c51be3e40326bc90c33ae69885bfb51e4 "Turn OStringLiteral into
a consteval'ed, static-refcound rtl_String".  Most remarks about that commit
apply here too (this commit is just substantially bigger and a bit more
complicated because there were so much more uses of OUStringLiteral than of
OStringLiteral):

The one downside is that OUStringLiteral now needs to be a template abstracting
over the string length.  But any uses for which that is a problem (e.g., as the
element type of a container that would no longer be homogeneous, or in the
signature of a function that shall not be turned into a template for one reason
or another) can be replaced with std::u16string_view, without loss of efficiency
compared to the original OUStringLiteral, and without loss of expressivity.

The new OUStringLiteral ctor code would probably not be very efficient if it
were ever executed at runtime, but it is intended to be only executed at compile
time.  Where available, C++20 "consteval" is used to statically ensure that.

The intended use of the new OUStringLiteral is in all cases where an
object that shall itself not be an OUString (e.g., because it shall be a
global static variable for which the OUString ctor/dtor would be detrimental at
library load/unload) must be converted to an OUString instance in at least one
place.  Other string literal abstractions could use std::u16string_view (or just
plain char16_t const[N]), but interestingly OUStringLiteral might be more
efficient than constexpr std::u16string_view even for such cases, as it should
not need any relocations at library load time.  For now, no existing uses of
OUStringLiteral have been changed to some other abstraction (unless technically
necessary as discussed above), and no additional places that would benefit from
OUStringLiteral have been changed to use it.

Global constexpr OUStringLiteral variables defined in an included file would be
somewhat suboptimal, as each translation unit that uses them would create its
own, unshared instance.  The envisioned solution is to turn them into static
data members of some class (and there may be a loplugin coming to find and fix
affected places).  Another approach that has been taken here in a few cases
where such variables were only used in one .cxx anyway is to move their
definitions from the .hxx into that one .cxx (in turn causing some files to
become empty and get removed completely)---which also silenced some GCC
-Werror=unused-variable if a variable from a .hxx was not used in some .cxx
including it.

To keep individual commits reasonably manageable, some consumers of
OUStringLiteral in rtl/ustrbuf.hxx and rtl/ustring.hxx are left in a somewhat
odd state for now, where they don't take advantage of OUStringLiteral's
equivalence to rtl_uString, but just keep extracting its contents and copy it
elsewhere.  In follow-up commits, those consumers should be changed
appropriately, making them treat OUStringLiteral like an rtl_uString or
dropping the OUStringLiteral overload in favor of an existing (and cheap to use
now) OUString overload, etc.

In a similar vein, comparison operators between OUString and std::u16string_view
have been added to the existing plethora of comparison operator overloads.  It
would be nice to eventually consolidate them, esp. with the overloads taking
OUStringLiteral and/or char16_t const[N] string literals, but that appears
tricky to get right without introducing new ambiguities.  Also, a handful of
places across the code base use comparisons between OUString and OUStringNumber,
which are now ambiguous (converting the OUStringNumber to either OUString or
std::u16string_view).  For simplicity, those few places have manually been fixed
for now by adding explicit conversion to std::u16string_view.

Also some compilerplugins code needed to be adapted, and some of the
compilerplugins/test cases have become irrelevant (and have been removed), as
the tested code would no longer compile in the first place.

sal/qa/rtl/strings/test_oustring_concat.cxx documents a workaround for GCC bug
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96878> "Failed class template
argument deduction in unevaluated, parenthesized context".  That place, as well
as uses of OUStringLiteral in extensions/source/abpilot/fieldmappingimpl.cxx and
i18npool/source/localedata/localedata.cxx, which have been replaced with
OUString::Concat (and which is arguably a better choice, anyway), also caused
failures with at least Clang 5.0.2 (but would not have caused failures with at
least recent Clang 12 trunk, so appear to be bugs in Clang that have meanwhile
been fixed).

Change-Id: I34174462a28f2000cfeb2d219ffd533a767920b8
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/102222
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

10 files changed, 27 insertions, 47 deletions

diff --git a/sdext/source/pdfimport/tree/drawtreevisiting.cxx b/sdext/source/pdfimport/tree/drawtreevisiting.cxx
index 387da6947c68..ebce9efc896b 100644
--- a/sdext/source/pdfimport/tree/drawtreevisiting.cxx
+++ b/sdext/source/pdfimport/tree/drawtreevisiting.cxx
@@ -35,6 +35,7 @@
 #include <com/sun/star/i18n/DirectionProperty.hpp>
 
 #include <string.h>
+#include <string_view>
 
 using namespace ::com::sun::star;
 using namespace ::com::sun::star::lang;
@@ -1034,7 +1035,7 @@ void DrawXmlFinalizer::visit( PageElement& elem, const std::list< std::unique_pt
     aPageLayoutProps[ "fo:margin-right" ]   =  unitMMString( right_margin );
     aPageLayoutProps[ "fo:page-width" ]     =  unitMMString( page_width );
     aPageLayoutProps[ "fo:page-height" ]    =  unitMMString( page_height );
-    aPageLayoutProps[ "style:print-orientation" ]= elem.w < elem.h ? OUStringLiteral(u"portrait") : OUStringLiteral(u"landscape");
+    aPageLayoutProps[ "style:print-orientation" ]= elem.w < elem.h ? std::u16string_view(u"portrait") : std::u16string_view(u"landscape");
     aPageLayoutProps[ "style:writing-mode" ]= "lr-tb";
 
     StyleContainer::Style aStyle( "style:page-layout", aPageProps);
diff --git a/sdext/source/pdfimport/tree/writertreevisiting.cxx b/sdext/source/pdfimport/tree/writertreevisiting.cxx
index 0ef3fe9144e5..79b799f7c9a3 100644
--- a/sdext/source/pdfimport/tree/writertreevisiting.cxx
+++ b/sdext/source/pdfimport/tree/writertreevisiting.cxx
@@ -17,6 +17,9 @@
  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  */
 
+#include <sal/config.h>
+
+#include <string_view>
 
 #include <pdfiprocessor.hxx>
 #include <xmlemitter.hxx>
@@ -1159,7 +1162,7 @@ void WriterXmlFinalizer::visit( PageElement& elem, const std::list< std::unique_
     aPageLayoutProps[ "fo:page-width" ]     = unitMMString( page_width );
     aPageLayoutProps[ "fo:page-height" ]    = unitMMString( page_height );
     aPageLayoutProps[ "style:print-orientation" ]
-        = elem.w < elem.h ? OUStringLiteral(u"portrait") : OUStringLiteral(u"landscape");
+        = elem.w < elem.h ? std::u16string_view(u"portrait") : std::u16string_view(u"landscape");
     aPageLayoutProps[ "fo:margin-top" ]     = unitMMString( top_margin );
     aPageLayoutProps[ "fo:margin-bottom" ]  = unitMMString( bottom_margin );
     aPageLayoutProps[ "fo:margin-left" ]    = unitMMString( left_margin );
diff --git a/sdext/source/presenter/PresenterConfigurationAccess.cxx b/sdext/source/presenter/PresenterConfigurationAccess.cxx
index 81aa31726d0b..467308426a26 100644
--- a/sdext/source/presenter/PresenterConfigurationAccess.cxx
+++ b/sdext/source/presenter/PresenterConfigurationAccess.cxx
@@ -33,9 +33,6 @@ using namespace ::com::sun::star::uno;
 
 namespace sdext::presenter {
 
-const OUStringLiteral PresenterConfigurationAccess::msPresenterScreenRootName =
-    u"/org.openoffice.Office.PresenterScreen/";
-
 PresenterConfigurationAccess::PresenterConfigurationAccess (
     const Reference<XComponentContext>& rxContext,
     const OUString& rsRootName,
diff --git a/sdext/source/presenter/PresenterConfigurationAccess.hxx b/sdext/source/presenter/PresenterConfigurationAccess.hxx
index 13b276fbfb92..bdd2c3afc9eb 100644
--- a/sdext/source/presenter/PresenterConfigurationAccess.hxx
+++ b/sdext/source/presenter/PresenterConfigurationAccess.hxx
@@ -52,7 +52,8 @@ public:
     typedef ::std::function<bool (
         const OUString&,
         const css::uno::Reference<css::beans::XPropertySet>&)> Predicate;
-    static const OUStringLiteral msPresenterScreenRootName;
+    static constexpr OUStringLiteral msPresenterScreenRootName =
+        u"/org.openoffice.Office.PresenterScreen/";
 
     /** Create a new object to access the configuration entries below the
         given root.
diff --git a/sdext/source/presenter/PresenterHelper.cxx b/sdext/source/presenter/PresenterHelper.cxx
index 4df88fd764a6..f66b4eb00a86 100644
--- a/sdext/source/presenter/PresenterHelper.cxx
+++ b/sdext/source/presenter/PresenterHelper.cxx
@@ -28,11 +28,9 @@ using namespace ::com::sun::star::presentation;
 
 namespace sdext::presenter {
 
-const OUStringLiteral PresenterHelper::msPaneURLPrefix( u"private:resource/pane/");
+const OUStringLiteral msPaneURLPrefix( u"private:resource/pane/");
 const OUString PresenterHelper::msFullScreenPaneURL( msPaneURLPrefix + "FullScreenPane");
 
-const OUStringLiteral PresenterHelper::msViewURLPrefix( u"private:resource/view/");
-
 Reference<presentation::XSlideShowController> PresenterHelper::GetSlideShowController (
     const Reference<frame::XController>& rxController)
 {
diff --git a/sdext/source/presenter/PresenterHelper.hxx b/sdext/source/presenter/PresenterHelper.hxx
index 8ba29e20e170..6704844d730c 100644
--- a/sdext/source/presenter/PresenterHelper.hxx
+++ b/sdext/source/presenter/PresenterHelper.hxx
@@ -30,11 +30,9 @@ namespace sdext::presenter {
 */
 namespace PresenterHelper
 {
-    extern const OUStringLiteral msPaneURLPrefix;
+    extern const OUString msCenterPaneURL;
     extern const OUString msFullScreenPaneURL;
 
-    extern const OUStringLiteral msViewURLPrefix;
-
     /** Return the slide show controller of a running presentation that has
         the same document as the given framework controller.
         @return
diff --git a/sdext/source/presenter/PresenterPaneFactory.cxx b/sdext/source/presenter/PresenterPaneFactory.cxx
index 14cf0ab92a69..a9c5bb907f25 100644
--- a/sdext/source/presenter/PresenterPaneFactory.cxx
+++ b/sdext/source/presenter/PresenterPaneFactory.cxx
@@ -33,17 +33,6 @@ using namespace ::com::sun::star::drawing::framework;
 
 namespace sdext::presenter {
 
-const OUStringLiteral PresenterPaneFactory::msCurrentSlidePreviewPaneURL(
-    u"private:resource/pane/Presenter/Pane1");
-const OUStringLiteral PresenterPaneFactory::msNextSlidePreviewPaneURL(
-    u"private:resource/pane/Presenter/Pane2");
-const OUStringLiteral PresenterPaneFactory::msNotesPaneURL(
-    u"private:resource/pane/Presenter/Pane3");
-const OUStringLiteral PresenterPaneFactory::msToolBarPaneURL(
-    u"private:resource/pane/Presenter/Pane4");
-const OUStringLiteral PresenterPaneFactory::msSlideSorterPaneURL(
-    u"private:resource/pane/Presenter/Pane5");
-
 //===== PresenterPaneFactory ==================================================
 
 Reference<drawing::framework::XResourceFactory> PresenterPaneFactory::Create (
diff --git a/sdext/source/presenter/PresenterPaneFactory.hxx b/sdext/source/presenter/PresenterPaneFactory.hxx
index 3a12481636ce..45f9541c65da 100644
--- a/sdext/source/presenter/PresenterPaneFactory.hxx
+++ b/sdext/source/presenter/PresenterPaneFactory.hxx
@@ -49,11 +49,14 @@ class PresenterPaneFactory
       public PresenterPaneFactoryInterfaceBase
 {
 public:
-    static const OUStringLiteral msCurrentSlidePreviewPaneURL;
-    static const OUStringLiteral msNextSlidePreviewPaneURL;
-    static const OUStringLiteral msNotesPaneURL;
-    static const OUStringLiteral msToolBarPaneURL;
-    static const OUStringLiteral msSlideSorterPaneURL;
+    static constexpr OUStringLiteral msCurrentSlidePreviewPaneURL
+        = u"private:resource/pane/Presenter/Pane1";
+    static constexpr OUStringLiteral msNextSlidePreviewPaneURL
+        = u"private:resource/pane/Presenter/Pane2";
+    static constexpr OUStringLiteral msNotesPaneURL = u"private:resource/pane/Presenter/Pane3";
+    static constexpr OUStringLiteral msToolBarPaneURL = u"private:resource/pane/Presenter/Pane4";
+    static constexpr OUStringLiteral msSlideSorterPaneURL
+        = u"private:resource/pane/Presenter/Pane5";
 
     /** Create a new instance of this class and register it as resource
         factory in the drawing framework of the given controller.
diff --git a/sdext/source/presenter/PresenterViewFactory.cxx b/sdext/source/presenter/PresenterViewFactory.cxx
index 0f107fb936b1..6a59a32935d7 100644
--- a/sdext/source/presenter/PresenterViewFactory.cxx
+++ b/sdext/source/presenter/PresenterViewFactory.cxx
@@ -33,19 +33,6 @@ using namespace ::com::sun::star::drawing::framework;
 
 namespace sdext::presenter {
 
-const OUStringLiteral PresenterViewFactory::msCurrentSlidePreviewViewURL(
-    u"private:resource/view/Presenter/CurrentSlidePreview");
-const OUStringLiteral PresenterViewFactory::msNextSlidePreviewViewURL(
-    u"private:resource/view/Presenter/NextSlidePreview");
-const OUStringLiteral PresenterViewFactory::msNotesViewURL(
-    u"private:resource/view/Presenter/Notes");
-const OUStringLiteral PresenterViewFactory::msToolBarViewURL(
-    u"private:resource/view/Presenter/ToolBar");
-const OUStringLiteral PresenterViewFactory::msSlideSorterURL(
-    u"private:resource/view/Presenter/SlideSorter");
-const OUStringLiteral PresenterViewFactory::msHelpViewURL(
-    u"private:resource/view/Presenter/Help");
-
 namespace {
 
 /** By default the PresenterSlidePreview shows the preview of the current
diff --git a/sdext/source/presenter/PresenterViewFactory.hxx b/sdext/source/presenter/PresenterViewFactory.hxx
index cc6aaea94ea7..30d488cfc0a7 100644
--- a/sdext/source/presenter/PresenterViewFactory.hxx
+++ b/sdext/source/presenter/PresenterViewFactory.hxx
@@ -75,12 +75,15 @@ class PresenterViewFactory
       public PresenterViewFactoryInterfaceBase
 {
 public:
-    static const OUStringLiteral msCurrentSlidePreviewViewURL;
-    static const OUStringLiteral msNextSlidePreviewViewURL;
-    static const OUStringLiteral msNotesViewURL;
-    static const OUStringLiteral msToolBarViewURL;
-    static const OUStringLiteral msSlideSorterURL;
-    static const OUStringLiteral msHelpViewURL;
+    static constexpr OUStringLiteral msCurrentSlidePreviewViewURL
+        = u"private:resource/view/Presenter/CurrentSlidePreview";
+    static constexpr OUStringLiteral msNextSlidePreviewViewURL
+        = u"private:resource/view/Presenter/NextSlidePreview";
+    static constexpr OUStringLiteral msNotesViewURL = u"private:resource/view/Presenter/Notes";
+    static constexpr OUStringLiteral msToolBarViewURL = u"private:resource/view/Presenter/ToolBar";
+    static constexpr OUStringLiteral msSlideSorterURL
+        = u"private:resource/view/Presenter/SlideSorter";
+    static constexpr OUStringLiteral msHelpViewURL = u"private:resource/view/Presenter/Help";
 
     /** Create a new instance of this class and register it as resource
         factory in the drawing framework of the given controller.