Whizard 3.0.0 doesn't compile with HepMC 3.2.3

[Kacper Nowak]

Dear Whizard authors,
after running "make && make install" I got following error (g++ 11.1.0, make 4.3, os Manjaro 21.0.7):
CXX libHepMCWrap_la-HepMC3RootWrap.lo
In file included from /usr/include/TString.h:29,
                 from /usr/include/TNamed.h:26,
                 from /usr/include/TDirectory.h:24,
                 from /usr/include/TDirectoryFile.h:25,
                 from /usr/include/TFile.h:28,
                 from /usr/include/HepMC3/ReaderRootTree.h:27,
                 from ../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp:14:
/usr/include/ROOT/RStringView.hxx:84:17: error: expected type-specifier
   84 | operator std::string_view() const { return std::string_view(fData,fLength); }
      | ^~~
In file included from /usr/include/TNamed.h:26,
                 from /usr/include/TDirectory.h:24,
                 from /usr/include/TDirectoryFile.h:25,
                 from /usr/include/TFile.h:28,
                 from /usr/include/HepMC3/ReaderRootTree.h:27,
                 from ../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp:14:
/usr/include/TString.h:115:13: error: expected type-specifier
  115 | operator std::string_view() const { return std::string_view(Data(),fExtent); }
      | ^~~
/usr/include/TString.h:280:32: error: ‘string_view’ in namespace ‘std’ does not name a type
  280 | explicit TString(const std::string_view &sub);
      | ^~~~~~~~~~~
/usr/include/TString.h:280:27: note: ‘std::string_view’ is only available from C++17 onwards
  280 | explicit TString(const std::string_view &sub);
      | ^~~
/usr/include/TString.h:317:37: error: ‘string_view’ in namespace ‘std’ does not name a type
  317 | TString &operator=(const std::string_view &s);
      | ^~~~~~~~~~~
/usr/include/TString.h:317:32: note: ‘std::string_view’ is only available from C++17 onwards
  317 | TString &operator=(const std::string_view &s);
      | ^~~
/usr/include/TString.h:444:9: error: ‘string_view’ in namespace ‘std’ does not name a type
  444 | std::string_view View() const { return std::string_view(GetPointer(),Length()); }
      | ^~~~~~~~~~~
/usr/include/TString.h:444:4: note: ‘std::string_view’ is only available from C++17 onwards
  444 | std::string_view View() const { return std::string_view(GetPointer(),Length()); }
      | ^~~
In file included from /usr/include/TNamed.h:26,
                 from /usr/include/TDirectory.h:24,
                 from /usr/include/TDirectoryFile.h:25,
                 from /usr/include/TFile.h:28,
                 from /usr/include/HepMC3/ReaderRootTree.h:27,
                 from ../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp:14:
/usr/include/TString.h:839:53: error: ‘string_view’ in namespace ‘std’ does not name a type
  839 | inline Bool_t operator==(const char *s1, const std::string_view &s2)
      | ^~~~~~~~~~~
/usr/include/TString.h:839:48: note: ‘std::string_view’ is only available from C++17 onwards
  839 | inline Bool_t operator==(const char *s1, const std::string_view &s2)
      | ^~~
/usr/include/TString.h:839:15: error: ‘Bool_t operator==(const char*, const int&)’ must have an argument of class or enumerated type
  839 | inline Bool_t operator==(const char *s1, const std::string_view &s2)
      | ^~~~~~~~
/usr/include/TString.h:844:37: error: ‘string_view’ in namespace ‘std’ does not name a type
  844 | inline Bool_t operator==(const std::string_view &s1, const char *s2)
      | ^~~~~~~~~~~
/usr/include/TString.h:844:32: note: ‘std::string_view’ is only available from C++17 onwards
  844 | inline Bool_t operator==(const std::string_view &s1, const char *s2)
      | ^~~
/usr/include/TString.h:844:15: error: ‘Bool_t operator==(const int&, const char*)’ must have an argument of class or enumerated type
  844 | inline Bool_t operator==(const std::string_view &s1, const char *s2)
      | ^~~~~~~~
/usr/include/TString.h:857:37: error: ‘string_view’ in namespace ‘std’ does not name a type
  857 | std::string printValue(const std::string_view* val);
      | ^~~~~~~~~~~
/usr/include/TString.h:857:32: note: ‘std::string_view’ is only available from C++17 onwards
  857 | std::string printValue(const std::string_view* val);
      | ^~~
In file included from /usr/include/HepMC3/ReaderRootTree.h:27,
                 from ../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp:14:
/usr/include/TFile.h:327:45: error: ‘std::string_view’ has not been declared
  327 | static Bool_t SetCacheFileDir(std::string_view cacheDir, Bool_t operateDisconnected = kTRUE,
      | ^~~~~~~~~~~
/usr/include/TFile.h: In static member function ‘static Bool_t TFile::SetCacheFileDir(ROOT::Internal::TStringView, Bool_t, Bool_t)’:
/usr/include/TFile.h:326:36: error: ‘string_view’ is not a member of ‘std’
  326 | { return SetCacheFileDir(std::string_view(cacheDir), operateDisconnected, forceCacheread); }
      | ^~~~~~~~~~~
/usr/include/TFile.h:326:36: note: ‘std::string_view’ is only available from C++17 onwards
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp: In function ‘HepMC3::GenVertex* gen_event_get_signal_process_vertex(HepMC3::GenEvent*)’:
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp:181:1: warning: no return statement in function returning non-void [-Wreturn-type]
  181 | }
      | ^
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp: In function ‘HepMC3::GenEvent* new_event_particle_const_iterator(HepMC3::GenEvent*)’:
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp:201:1: warning: no return statement in function returning non-void [-Wreturn-type]
  201 | }
      | ^
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp: In function ‘HepMC3::GenParticlePtr event_particle_const_iterator_get(HepMC3::GenEvent*)’:
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp:226:1: warning: no return statement in function returning non-void [-Wreturn-type]
  226 | }
      | ^
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp: In function ‘HepMC3::GenVertex* new_vertex_particles_in_const_iterator(HepMC3::GenVertex*)’:
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp:287:1: warning: no return statement in function returning non-void [-Wreturn-type]
  287 | }
      | ^
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp: In function ‘HepMC3::GenParticlePtr vertex_particles_in_const_iterator_get(HepMC3::GenVertex*)’:
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp:312:1: warning: no return statement in function returning non-void [-Wreturn-type]
  312 | }
      | ^
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp: In function ‘HepMC3::GenVertex* new_vertex_particles_out_const_iterator(HepMC3::GenVertex*)’:
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp:326:1: warning: no return statement in function returning non-void [-Wreturn-type]
  326 | }
      | ^
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp: In function ‘HepMC3::GenParticlePtr vertex_particles_out_const_iterator_get(HepMC3::GenVertex*)’:
../../../whizard-3.0.0/src/hepmc/HepMC3RootWrap.cpp:351:1: warning: no return statement in function returning non-void [-Wreturn-type]
  351 | }
      | ^

Regards,
Kacper Nowak

[Juergen Reuter (j.r.reuter)]

Hi Kacper,
this seems not to be a bug, but an incompatibility between different C++ standards between HepMC3, ROOT, and the WHIZARD interfaces. How did you install ROOT and HepMC3? Did you compile yourself or did you use system packages? string_view is a C++17 feature, so some of your three programs have not been compiled with that compiler or with those flags. Try configuring WHIZARD with the setting
CXXFLAGS="--std=c++17".

[Kacper Nowak (anarion19)]

Dear Juergen,
thank you for quick reply. I've installed both HepMC and ROOT 6.24.00 from official
Manjaro repository.
I've tried configuring WHIZARD with c++17 flag but the result is the same.

[Juergen Reuter (j.r.reuter)]

Dear Kacper,
could you check the following WHIZARD snapshot, please:
https://whizard.hepforge.org/versions/unofficial/whizard-3.0.0+_20210705.tar.gz
Let me know if you encounter the same problem.
Cheers,
   JRR

[Kacper Nowak (anarion19)]

Thank you very much! It compiles now, but the tests fail. I attach test-suite.log
Cheers,
Kacper

[Juergen Reuter (j.r.reuter)]

Thanks for reporting. This will be fixed for v3.0.1 to be expected within 2-3 weeks.
Your tests are failing because you need to include the Openloops libraries to your LD_LIBRARY_PATH,
e.g.
export LD_LIBRARY_PATH=<openloops_path>/lib:$LD_LIBRARY_PATH