Silence bogus -Werror=redundant-move (GCC 9)

Change-Id: Ia078fb8e1e497edfa08e2a61d1659100461fc52e
Reviewed-on: https://gerrit.libreoffice.org/59720
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Reviewed-on: https://gerrit.libreoffice.org/66914Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Tested-by: Jan Holesovsky <kendy@collabora.com>

config_host/config_global.h.in

@@ -23,4 +23,8 @@ Any change in this header will cause a rebuild of almost everything.
 /* Compiler supports __attribute__((warn_unused)). */
 #define HAVE_GCC_ATTRIBUTE_WARN_UNUSED 0
 
+/* GCC bug <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87150> "move ctor wrongly chosen in return
+   stmt (derived vs. base)": */
+#define HAVE_GCC_BUG_87150 0
+
 #endif

configure.ac

@@ -6191,6 +6191,21 @@ if test "$GCC" = yes; then
 fi
 AC_SUBST([HAVE_GCC_FNO_SIZED_DEALLOCATION])
 
+AC_MSG_CHECKING([whether $CXX has GCC bug 87150])
+AC_LANG_PUSH([C++])
+save_CXXFLAGS=$CXXFLAGS
+CXXFLAGS="$CXXFLAGS $CXXFLAGS_CXX11"
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([
+        struct S1 { S1(S1 &&); };
+        struct S2: S1 {};
+        S1 f(S2 s) { return s; }
+    ])], [
+        AC_DEFINE([HAVE_GCC_BUG_87150],[1])
+        AC_MSG_RESULT([yes])
+    ], [AC_MSG_RESULT([no])])
+CXXFLAGS=$save_CXXFLAGS
+AC_LANG_POP([C++])
+
 dnl ===================================================================
 dnl system stl sanity tests
 dnl ===================================================================

editeng/source/editeng/editeng.cxx

@@ -19,6 +19,7 @@
 
 #include <memory>
 #include <comphelper/lok.hxx>
+#include <config_global.h>
 #include <vcl/wrkwin.hxx>
 #include <vcl/dialog.hxx>
 #include <vcl/msgbox.hxx>
@@ -2624,7 +2625,11 @@ vcl::Font EditEngine::CreateFontFromItemSet( const SfxItemSet& rItemSet, SvtScri
 {
     SvxFont aFont;
     CreateFont( aFont, rItemSet, true, nScriptType );
+#if HAVE_GCC_BUG_87150
+    return aFont;
+#else
     return std::move(aFont);
+#endif
 }
 
 SvxFont EditEngine::CreateSvxFontFromItemSet( const SfxItemSet& rItemSet )