Make brittle SortedAutoCompleteStrings ownership handling more explicit

Change-Id: Ieaf2231a84d97528bb1b9a410c4ee0c38966dd27
Reviewed-on: https://gerrit.libreoffice.org/56950
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

config_host/config_global.h.in

@@ -23,4 +23,7 @@ Any change in this header will cause a rebuild of almost everything.
 /* Compiler supports __attribute__((warn_unused)). */
 #define HAVE_GCC_ATTRIBUTE_WARN_UNUSED 0
 
+/* Guaranteed copy elision (C++17), __cpp_guaranteed_copy_elision (C++2a): */
+#define HAVE_CPP_GUARANTEED_COPY_ELISION 0
+
 #endif

configure.ac

@@ -6482,6 +6482,29 @@ if test "$GCC" = yes; then
 fi
 AC_SUBST([HAVE_GCC_FNO_SIZED_DEALLOCATION])
 
+HAVE_CPP_GUARANTEED_COPY_ELISION=
+AC_MSG_CHECKING([whether $CXX supports guaranteed copy elision])
+AC_LANG_PUSH([C++])
+save_CXXFLAGS=$CXXFLAGS
+CXXFLAGS="$CXXFLAGS $CXXFLAGS_CXX11"
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([
+        #if !defined __cpp_guaranteed_copy_elision
+        struct S {
+        private:
+            S(S const &);
+        public:
+            S copy() const { return *this; }
+        };
+        void f(S & s) { S c(s.copy()); }
+        #endif
+    ])], [
+        AC_DEFINE([HAVE_CPP_GUARANTEED_COPY_ELISION],[1])
+        AC_MSG_RESULT([yes])
+    ], [AC_MSG_RESULT([no])])
+CXXFLAGS=$save_CXXFLAGS
+AC_LANG_POP([C++])
+AC_SUBST([HAVE_CPP_GUARANTEED_COPY_ELISION])
+
 dnl ===================================================================
 dnl system stl sanity tests
 dnl ===================================================================

include/editeng/swafopt.hxx

@@ -20,6 +20,9 @@
 #ifndef INCLUDED_EDITENG_SWAFOPT_HXX
 #define INCLUDED_EDITENG_SWAFOPT_HXX
 
+#include <sal/config.h>
+
+#include <config_global.h>
 #include <editeng/editengdllapi.h>
 #include <o3tl/sorted_vector.hxx>
 #include <rtl/ustring.hxx>
@@ -52,8 +55,23 @@ struct CompareAutoCompleteString
 class SortedAutoCompleteStrings
   : public o3tl::sorted_vector<IAutoCompleteString*, CompareAutoCompleteString>
 {
+    bool owning_;
+
+    void operator =(SortedAutoCompleteStrings) = delete;
+
+#if !HAVE_CPP_GUARANTEED_COPY_ELISION
+public:
+#endif
+    // For createNonOwningCopy only:
+    SortedAutoCompleteStrings(SortedAutoCompleteStrings const & other):
+        sorted_vector(other), owning_(false) {}
+
 public:
-    ~SortedAutoCompleteStrings() { DeleteAndDestroyAll(); }
+    SortedAutoCompleteStrings(): owning_(true) {}
+
+    ~SortedAutoCompleteStrings() { if (owning_) DeleteAndDestroyAll(); }
+
+    SortedAutoCompleteStrings createNonOwningCopy() const { return *this; }
 };
 
 } // namespace editeng

sw/source/uibase/app/docsh2.cxx

@@ -421,7 +421,7 @@ void SwDocShell::Execute(SfxRequest& rReq)
 
             rACW.SetLockWordLstLocked( true );
 
-            editeng::SortedAutoCompleteStrings aTmpLst( rACW.GetWordList() );
+            editeng::SortedAutoCompleteStrings aTmpLst( rACW.GetWordList().createNonOwningCopy() );
             pAFlags->m_pAutoCompleteList = &aTmpLst;
 
             SfxApplication* pApp = SfxGetpApp();
@@ -455,8 +455,6 @@ void SwDocShell::Execute(SfxRequest& rReq)
                 // clear the temp WordList pointer
                 pAFlags->m_pAutoCompleteList = nullptr;
             }
-            // remove all pointer we never delete the strings
-            aTmpLst.clear();
 
             if( !bOldAutoCmpltCollectWords && bOldAutoCmpltCollectWords !=
                 pAFlags->bAutoCmpltCollectWords )