Wt

With Debian stretch (testing) and g "(Debian 6.2.1-5) 6.2.1 20161124", a build of Wt4 preview (github 3.3.6-16-ged99039c) results in numerous placement new warnings. Here's an example for WComboBox.C (with abbreviated paths).

cd /wt4p-static-build/src && /usr/bin/c++   -DBOOST_SPIRIT_THREADSAFE -DGLEW_STATIC -DHAVE_GRAPHICSMAGICK -DHAVE_PANGO -DHAVE_PDF_IMAGE -DQT_CORE_LIB -DQT_GUI_LIB -DQT_NO_DEBUG -DWT_BUILDING -DWT_WITH_OLD_INTERNALPATH_API -D_REENTRANT -I/wt4p-static-build -I/wt4p/src/web -I/wt4p/src -I/wt4p-static-build/src -I/wt4p/src/Wt/Dbo/backend/amalgamation -I/wt4p/src/3rdparty/glew-1.10.0/include -isystem /usr/include/qt4 -isystem /usr/include/qt4/QtGui -isystem /usr/include/qt4/QtCore -I/x/boost/boost_1_62/include/boost-1_62 -I/x/libharu/include -I/usr/include/GraphicsMagick -I/usr/include/pango-1.0 -I/usr/include/freetype2 -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include  -g -std=c++14 -B/usr/lib/gold-ld -std=c++14 -O2 -g -DNDEBUG   -o CMakeFiles/wt.dir/Wt/WComboBox.o -c /wt4p/src/Wt/WComboBox.C
In file included from /wt4p/src/Wt/cpp17/any.hpp:78:0,
                 from /wt4p/src/Wt/WAny:11,
                 from /wt4p/src/Wt/WAny.h:7,
                 from /wt4p/src/Wt/WModelIndex:15,
                 from /wt4p/src/Wt/WModelIndex.h:7,
                 from /wt4p/src/Wt/WAbstractItemModel:11,
                 from /wt4p/src/Wt/WAbstractItemModel.h:7,
                 from /wt4p/src/Wt/WAbstractListModel:10,
                 from /wt4p/src/Wt/WAbstractListModel.h:7,
                 from /wt4p/src/Wt/WStringListModel:10,
                 from /wt4p/src/Wt/WStringListModel.h:7,
                 from /wt4p/src/Wt/WComboBox.C:9:
/wt4p/src/Wt/cpp17/any/any.hpp: In instantiation of ‘void linb::any::construct(ValueType&&) [with ValueType = const Wt::WString&]’:
/wt4p/src/Wt/cpp17/any/any.hpp:81:9:   required from ‘linb::any::any(ValueType&&) [with ValueType = const Wt::WString&; <template-parameter-1-2> = void]’
/wt4p/src/Wt/WComboBox.C:162:55:   required from here
/wt4p/src/Wt/cpp17/any/any.hpp:350:13: warning: placement new constructing an object of type ‘T {aka Wt::WString}’ and size ‘40’ in a region of type ‘linb::any::storage_union::stack_storage_t {aka std::aligned_storage<16ul, 8ul>::type}’ and size ‘16’ [-Wplacement-new=]
             new (&storage.stack) T(std::forward<ValueType>(value));
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It looks like the compiler warnings may be inaccurate; there's an open gcc bug report that seems relevant here: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70834.

The issue is also triggered with upstream's test_any.cpp. If the compiler warning is confirmed to be incorrect, it can be suppressed with pragmas in any.hpp.

The preview looks great, by the way. I'm looking forward to testing it with some apps. Thanks for releasing it!