Address a constexpr template point of instantiation issue

...that hits at least when building with Clang and --with-latest-c++ against
recent libc++ or MSVC standard library (where C++20 and esp. C++23 made more and
more class template member functions constexpr).  My understanding is that there
is some leeway at what point a compiler should instantiate such function
specializations, and Clang decides to instantiate constexpr ones early (cf.
<https://github.com/llvm/llvm-project/commit/242ad89a15d5466d166d47978bfff983d40ab511>
"C++11 half of r147023: In C++11, additionally eagerly instantiate:" and its "Do
not defer instantiations of constexpr functions" comment, and the discussion at
<https://discourse.llvm.org/t/point-of-instantiation-of-constexpr-function-template/65129>).

> In file included from starmath/source/ElementsDockingWindow.cxx:20:
> In file included from starmath/inc/ElementsDockingWindow.hxx:22:
> In file included from include/sfx2/dockwin.hxx:22:
> In file included from ~/llvm/inst/bin/../include/c++/v1/memory:881:
> In file included from ~/llvm/inst/bin/../include/c++/v1/__memory/shared_ptr.h:30:
> ~/llvm/inst/bin/../include/c++/v1/__memory/unique_ptr.h:47:19: error: invalid application of 'sizeof' to an incomplete type 'ElementData'
>     static_assert(sizeof(_Tp) >= 0, "cannot delete an incomplete type");
>                   ^~~~~~~~~~~
> ~/llvm/inst/bin/../include/c++/v1/__memory/unique_ptr.h:281:7: note: in instantiation of member function 'std::default_delete<ElementData>::operator()' requested here
>       __ptr_.second()(__tmp);
>       ^
> ~/llvm/inst/bin/../include/c++/v1/__memory/unique_ptr.h:247:75: note: in instantiation of member function 'std::unique_ptr<ElementData>::reset' requested here
>   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 ~unique_ptr() { reset(); }
>                                                                           ^
> ~/llvm/inst/bin/../include/c++/v1/__memory/construct_at.h:64:13: note: in instantiation of member function 'std::unique_ptr<ElementData>::~unique_ptr' requested here
>     __loc->~_Tp();
>             ^
> ~/llvm/inst/bin/../include/c++/v1/__memory/construct_at.h:89:12: note: in instantiation of function template specialization 'std::__destroy_at<std::unique_ptr<ElementData>, 0>' requested here
>     _VSTD::__destroy_at(__loc);
>            ^
> ~/llvm/inst/bin/../include/c++/v1/__memory/allocator_traits.h:317:16: note: in instantiation of function template specialization 'std::destroy_at<std::unique_ptr<ElementData>, 0>' requested here
>         _VSTD::destroy_at(__p);
>                ^
> ~/llvm/inst/bin/../include/c++/v1/vector:834:25: note: in instantiation of function template specialization 'std::allocator_traits<std::allocator<std::unique_ptr<ElementData>>>::destroy<std::unique_ptr<ElementData>, void, void>' requested here
>         __alloc_traits::destroy(__alloc(), std::__to_address(--__soon_to_be_end));
>                         ^
> ~/llvm/inst/bin/../include/c++/v1/vector:828:29: note: in instantiation of member function 'std::vector<std::unique_ptr<ElementData>>::__base_destruct_at_end' requested here
>   void __clear() _NOEXCEPT {__base_destruct_at_end(this->__begin_);}
>                             ^
> ~/llvm/inst/bin/../include/c++/v1/vector:433:9: note: in instantiation of member function 'std::vector<std::unique_ptr<ElementData>>::__clear' requested here
>         __clear();
>         ^
> starmath/source/ElementsDockingWindow.cxx:455:20: note: in instantiation of member function 'std::vector<std::unique_ptr<ElementData>>::~vector' requested here
> SmElementsControl::SmElementsControl(std::unique_ptr<weld::IconView> pIconView)
>                    ^
> starmath/inc/ElementsDockingWindow.hxx:35:8: note: forward declaration of 'ElementData'
> struct ElementData;
>        ^

Change-Id: Iaae76ed5e59d04da32b468a69052ef305ca8005a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/141819
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

1 files changed, 11 insertions, 11 deletions

diff --git a/starmath/source/ElementsDockingWindow.cxx b/starmath/source/ElementsDockingWindow.cxx
index c332c5afda2d..0444db4ba42a 100644
--- a/starmath/source/ElementsDockingWindow.cxx
+++ b/starmath/source/ElementsDockingWindow.cxx
@@ -452,6 +452,17 @@ const std::vector<TranslateId>& SmElementsControl::categories()
     return s_a5Categories;
 }
 
+struct ElementData
+{
+    OUString maElementSource;
+    OUString maHelpText;
+    ElementData(const OUString& aElementSource, const OUString& aHelpText)
+        : maElementSource(aElementSource)
+        , maHelpText(aHelpText)
+    {
+    }
+};
+
 SmElementsControl::SmElementsControl(std::unique_ptr<weld::IconView> pIconView)
     : mpDocShell(new SmDocShell(SfxModelFlags::EMBEDDED_OBJECT))
     , mnCurrentSetIndex(-1)
@@ -482,17 +493,6 @@ Color SmElementsControl::GetControlBackground()
     return rStyleSettings.GetFieldColor();
 }
 
-struct ElementData
-{
-    OUString maElementSource;
-    OUString maHelpText;
-    ElementData(const OUString& aElementSource, const OUString& aHelpText)
-        : maElementSource(aElementSource)
-        , maHelpText(aHelpText)
-    {
-    }
-};
-
 void SmElementsControl::addElement(const OUString& aElementVisual, const OUString& aElementSource, const OUString& aHelpText)
 {
     std::unique_ptr<SmNode> pNode = maParser->ParseExpression(aElementVisual);