(in)compatibility with pybind11 3.0.0

[francesco-ballarin]

Hi,
pybind11 3.0.0 was released last week. After upgrading to that version, and using system pybind11 rather than the one shipped as a git submodule in the netgen git repo, one of my CIs started failing upon importing netgen with

root@fef5125263f2:~# python3 -c 'import ngsolve'


Caught exception:
arg(): could not convert default argument into a Python object (type not registered yet?). #define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for more information.
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/local/lib/python3.11/dist-packages/ngsolve/__init__.py", line 38, in <module>
    from .ngslib import __version__, ngstd, bla, la, fem, comp, solve
ImportError: cannot import name 'fem' from 'ngsolve' (/usr/local/lib/python3.11/dist-packages/ngsolve/ngslib.so)

Can you add a test with the newest pybind on your CI?

[ChrLackner]

I just compiled netgen and ngsolve with pybnid11 3.0.0 and everything works. Are you sure you compiled both? The error I get when I only recompile netgen but not ngsolve with new pybind11

[francesco-ballarin]

The error I get when I only recompile netgen but not ngsolve with new pybind11

Thanks @ChrLackner , this put me on the right track. I thought I was recompiling both with system pybind11, but I had forgotten to pass -DPREFER_SYSTEM_PYBIND11:BOOL=ON when building netgen.