openbabel build fails to set correct C++ standard: C++14 is required by eigen3 (at least by -devel)

[barracuda156]

Error with eigen3:

:info:build [  8%] Building CXX object src/CMakeFiles/openbabel.dir/builder.cpp.o
:info:build cd /opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_science_openbabel/openbabel/work/build/src && /opt/local/bin/g++-mp-13 -DHAVE_EIGEN -DHAVE_EIGEN3 -DHAVE_LIBZ -DHAVE_RADPIJSON -DHAVE_SHARED_POINTER -DHAVE_WXWIDGETS -DMAKE_OBDLL -DUSING_DYNAMIC_LIBS -D_FILE_OFFSET_BITS=64 -D_LARGE_FILES -D__WXDEBUG__ -D__WXMAC__ -I/opt/local/include -I/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_science_openbabel/openbabel/work/build/include -I/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_science_openbabel/openbabel/work/openbabel-3.1.1/data -I/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_science_openbabel/openbabel/work/openbabel-3.1.1/include -I/opt/local/include/eigen3 -isystem /usr/lib/wx/include/mac-unicode-debug-2.8 -isystem /usr/include/wx-2.8 -pipe -Os -DNDEBUG -I/opt/local/include -D_GLIBCXX_USE_CXX11_ABI=0 -std=gnu++11 -arch ppc -mmacosx-version-min=10.6 -fPIC -MD -MT src/CMakeFiles/openbabel.dir/builder.cpp.o -MF CMakeFiles/openbabel.dir/builder.cpp.o.d -o CMakeFiles/openbabel.dir/builder.cpp.o -c /opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_science_openbabel/openbabel/work/openbabel-3.1.1/src/builder.cpp
:info:build In file included from /opt/local/include/eigen3/Eigen/Core:19,
:info:build                  from /opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_science_openbabel/openbabel/work/openbabel-3.1.1/include/openbabel/distgeom.h:34,
:info:build                  from /opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_science_openbabel/openbabel/work/openbabel-3.1.1/src/builder.cpp:33:
:info:build /opt/local/include/eigen3/Eigen/src/Core/util/Macros.h:712:2: error: #error This compiler appears to be too old to be supported by Eigen
:info:build   712 | #error This compiler appears to be too old to be supported by Eigen
:info:build       |  ^~~~~

This happens because it requires C++14, while the build uses C++11:

#if EIGEN_MAX_CPP_VER < 14 || EIGEN_COMP_CXXVER < 14 || \
  (EIGEN_COMP_MSVC && EIGEN_COMP_MSVC < 1900) || \
  (EIGEN_COMP_ICC && EIGEN_COMP_ICC < 1500) || \
  (EIGEN_COMP_NVCC && EIGEN_COMP_NVCC < 80000) || \
  (EIGEN_COMP_CLANG_STRICT && EIGEN_COMP_CLANG < 390) || \
  (EIGEN_COMP_CLANGAPPLE && EIGEN_COMP_CLANGAPPLE < 9000000) || \
  (EIGEN_COMP_GNUC_STRICT && EIGEN_COMP_GNUC < 510)
#error This compiler appears to be too old to be supported by Eigen
#endif

[barracuda156]

Also, if it actually uses Python for anything, perhaps it should use Macports one:

Found PythonInterp: /usr/bin/python (found version "2.5.1") 

16. S. And is it correct that is uses system wxWidgets?

    /usr/include/wx-2.8
    

(I am not saying that is wrong; Macports wxWidgets seems to have issues on old systems, so it could be that the old system one is actually preferable. Needs to be verified.)

[barracuda156]

By the way, I can confirm that once C++ standard is set to 14, no more disaster with Eigen.

[barracuda156]

On a side note, I have opened an issue with Eigen re that silly error, hopefully they gonna fix it: ​https://gitlab.com/libeigen/eigen/-/issues/2741 It is really confusing atm.

[reneeotten (Renee Otten)]

Replying to barracuda156:

By the way, I can confirm that once C++ standard is set to 14, no more disaster with Eigen.

well eigen3 claims itself to be needing CXX11 so if that's indeed correct there should be no need for openbabel to require anything else.

[reneeotten (Renee Otten)]

Replying to barracuda156:

Also, if it actually uses Python for anything, perhaps it should use Macports one:

Found PythonInterp: /usr/bin/python (found version "2.5.1") 

16. S. And is it correct that is uses system wxWidgets?

    /usr/include/wx-2.8
    

(I am not saying that is wrong; Macports wxWidgets seems to have issues on old systems, so it could be that the old system one is actually preferable. Needs to be verified.)

that indeed doesn't seem right, but I cannot recall having seen that before - I can take a look at some point...

[reneeotten (Renee Otten)]

with what variants are you installing this - it doesn't install any Python bindings so I don't think it should be using it

[barracuda156]

Replying to reneeotten:

Replying to barracuda156:

By the way, I can confirm that once C++ standard is set to 14, no more disaster with Eigen.

well eigen3 claims itself to be needing CXX11 so if that's indeed correct there should be no need for openbabel to require anything else.

I have quoted eigen3 header above: the current version does require C++14. Possibly, the older one is at C++11.

[barracuda156]

Replying to reneeotten:

with what variants are you installing this - it doesn't install any Python bindings so I don't think it should be using it

Whatever default was. I think CMake does not use Python, just checked for it.

[barracuda156]

So it looks like gui is not default, so no wxWidgets should have been used, but the linking flag is still passed.

Also wxWidgets-3.2 is definitely broken on old systems atm; if it support 2.8 or 3.0, it should be conditionally preferred. (May not save PowerPC, as of now, but should help older Intel.)