call of overloaded rb_define_virtual_variable is ambiguous

[majioa]

Hello I've got the many following errors during compilation ruby module:

cd /usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/x86_64-alt-linux/src && /usr/bin/c++ -DCANORUS_VERSION=\"0.8.0rc1\" -DCanorusRuby_EXPORTS -DDEFAULT_DATA_DIR=\"/usr/share/canorus\" -DQT_CORE_LIB -DQT_GUI_LIB -DQT_NO_DEBUG -DQT_PRINTSUPPORT_LIB -DQT_SVG_LIB -DQT_WIDGETS_LIB -DQT_XML_LIB -DUSE_RUBY -DUSE_SWIG -D__LINUX_ALSA__ -I/usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/src -I/usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/src/zlib -I/usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/src/core -I/usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/src/ui -I/usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/src/widgets -I/usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/src/import -I/usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/x86_64-alt-linux/src -I/usr/include/x86_64-linux -isystem /usr/include/qt5 -isystem /usr/include/qt5/QtCore -isystem /usr/share/qt5/../../lib64/qt5/mkspecs/linux-g++ -isystem /usr/include/qt5/QtGui -isystem /usr/include/qt5/QtSvg -isystem /usr/include/qt5/QtWidgets -isystem /usr/include/qt5/QtXml -isystem /usr/include/qt5/QtPrintSupport -pipe -frecord-gcc-switches -Wall -g -O2 -flto=auto -Wno-error=deprecated-declarations -Wno-error=return-type -Wno-error -O2 -Wno-error=deprecated-declarations -Wno-error=return-type -Wno-deprecated-declarations -Wno-return-type -Wno-unused-variable -Wno-error -fPIC -DSWIGCPP -Wno-error=deprecated-declarations -Wno-return-type -fPIC -std=gnu++14 -MD -MT src/CMakeFiles/CanorusRuby.dir/canorusrubyRUBY_wrap.cxx.o -MF CMakeFiles/CanorusRuby.dir/canorusrubyRUBY_wrap.cxx.o.d -o CMakeFiles/CanorusRuby.dir/canorusrubyRUBY_wrap.cxx.o -c /usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/x86_64-alt-linux/src/canorusrubyRUBY_wrap.cxx
/usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/x86_64-alt-linux/src/canorusrubyRUBY_wrap.cxx: In function 'void SWIG_RubyInitializeTrackings()':
/usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/x86_64-alt-linux/src/canorusrubyRUBY_wrap.cxx:1263:29: error: call of overloaded 'rb_define_virtual_variable(const char [21], VALUE (&)(...), NULL)' is ambiguous
 1263 |   rb_define_virtual_variable("SWIG_TRACKINGS_COUNT", swig_ruby_trackings_count, NULL);
      |   ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/ruby/ruby.h:2863,
                 from /usr/include/ruby.h:33,
                 from /usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/x86_64-alt-linux/src/canorusrubyRUBY_wrap.cxx:879:
/usr/include/ruby/backward/cxxanyargs.hpp:59:1: note: candidate: 'void ruby::backward::cxxanyargs::rb_define_virtual_variable(const char*, VALUE (*)(...), void (*)(...))'
   59 | rb_define_virtual_variable(const char *q, type *w, void_type *e)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/ruby/backward/cxxanyargs.hpp:90:1: note: candidate: 'void ruby::backward::cxxanyargs::rb_define_virtual_variable(const char*, VALUE (*)(...), void (*)(VALUE, ID, VALUE*))'
   90 | rb_define_virtual_variable(const char *q, type *w, rb_gvar_setter_t *e)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~
gmake[2]: *** [src/CMakeFiles/CanorusRuby.dir/build.make:136: src/CMakeFiles/CanorusRuby.dir/canorusrubyRUBY_wrap.cxx.o] Error 1
gmake[2]: Leaving directory '/usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/x86_64-alt-linux'
gmake[2]: *** Waiting for unfinished jobs....
gmake[2]: Entering directory '/usr/src/RPM/BUILD/canorus-0.7.3.git45e82ec/x86_64-alt-linux'

It seems that some erroneous code for function rb_define_virtual_variable is used. So, how it can be fixed?

[matevz]

Ruby support is a bit rusty. If you don't need ruby support, you can always do cmake -DNO_RUBY=1 to avoid ruby-related compilation errors.

[suamor]

I remember that the python swig interface had similar problems, so we should have a look how it was fixed on python side.
Apart from that we discussed it a few years ago what should happen with our binding interface but did not come to a final conclusion.

Generally I don't see a way around swig itself. Most programs use only one scripting language for plugin (and python is very commonly used as well as Lua).

In the notation case a lot of languages make sense to have support without the pain to implement a specific language binding interface.

Back to ruby (and this is similar for all languages), one person is needed that has experience in this kind of language. Regarding me while I like ruby as language over python (2.x) I had no opportunities in my projects to use it.

Another problem is that Qt6 is getting more and more important and we need to do the switch relatively soon. On the other hand ruby does not have any qt5 support and is not listed as qt supported language.

This means anything you do on UI level requiring Qt you need to handle via an extra Ruby specific interface (i.e. "simple" types like qstring, qlist, qint needs to be converted to their ruby types).

Summarized currently ruby support cannot be done by Canorus because of lack of Qt by ruby itself. When somebody with ruby experience comes up with solutions how to interface ruby we will gladly support it.