CMake compile fails without C++17 Standard

[j-signorelli]

Hi,

I am unable to compile GLVis using CMake with the current master branches of both unless I update the CXX standard in CMakeLists.txt from

set(CMAKE_CXX_STANDARD 11)

to

set(CMAKE_CXX_STANDARD 17)

The build fails with all errors related to not using C++17, like:

In file included from /home/j-signorelli/software/mfem/git_repo/linalg/linalg.hpp:40,
                 from /home/j-signorelli/software/mfem/git_repo/mfem.hpp:45,
                 from /home/j-signorelli/software/mfem/git_repo/build/mfem.hpp:3,
                 from /home/j-signorelli/software/mfem/glvis/lib/gl/../openglvis.hpp:19,
                 from /home/j-signorelli/software/mfem/glvis/lib/gl/../aux_vis.hpp:18,
                 from /home/j-signorelli/software/mfem/glvis/lib/gl/renderer_core.cpp:14:
/home/j-signorelli/software/mfem/git_repo/linalg/filteredsolver.hpp: In constructor ‘mfem::AMGFSolver::AMGFSolver()’:
/home/j-signorelli/software/mfem/git_repo/linalg/filteredsolver.hpp:130:18: error: ‘make_unique’ is not a member of ‘std’
  130 |       amg = std::make_unique<HypreBoomerAMG>();
      |                  ^~~~~~~~~~~
/home/j-signorelli/software/mfem/git_repo/linalg/filteredsolver.hpp:130:18: note: ‘std::make_unique’ is only available from C++14 onwards

Should this be updated since MFEM now uses C++17? Or is there something I am doing wrong on my end?

Thanks for any input!

[najlkin]

Hi, no, it is not wrong on your end. We have just almost not touched GLVis from the last release 😅 . We should definitely change this latest when MFEM 4.9 gets out. The rule is that it should build with the latest release. Maybe you could try it the other way around, i.e., building it with the modified CMake and MFEM 4.8? That would be helpful to confirm it does not cause problems that way 🤔 .

[j-signorelli]

Thanks! Just tested it using 4.8 and it appears to work just fine. I'll go ahead and submit a PR 👍