building with CGAL 5

[drew-parsons]

pygalmesh needs some help to build against CGAL 5, which is now header-only.

Dropping the CGAL libraries themselves is easy enough. (I guess you'd want the build able to work with both CGAL 4 or 5)

But then there's a more subtle problem (on Debian unstable). setup.py seems to be invoking gcc to compile the extensions, but the files are C++. setup.py does refer to C++, but nevertheless the build proceeds with x86_64-linux-gnu-gcc instead of x86_64-linux-gnu-g++.

Consequently when running tests,

   dh_auto_test -O--buildsystem=pybuild
I: pybuild base:217: cd /home/projects/pygalmesh/.pybuild/cpython3_3.8_pygalmesh/build; python3.8 -m unittest discover -v 
pygalmesh (unittest.loader._FailedTest) ... ERROR

======================================================================
ERROR: pygalmesh (unittest.loader._FailedTest)
----------------------------------------------------------------------
ImportError: Failed to import test module: pygalmesh
Traceback (most recent call last):
  File "/usr/lib/python3.8/unittest/loader.py", line 470, in _find_test_path
    package = self._get_module_from_name(name)
  File "/usr/lib/python3.8/unittest/loader.py", line 377, in _get_module_from_name
    __import__(name)
  File "/home/projects/pygalmesh/.pybuild/cpython3_3.8_pygalmesh/build/pygalmesh/__init__.py", line 2, in <module>
    from _pygalmesh import (
ImportError: /home/projects/pygalmesh/.pybuild/cpython3_3.8_pygalmesh/build/_pygalmesh.cpython-38-x86_64-linux-gnu.so: undefined symbol: _ZTVN10__cxxabiv117__class_type_infoE

The missing symbol is in libstdc++.so.

[drew-parsons]

Joachim Reichel suggests it needs
libraries=["stdc++", "gmp", "mpfr"]

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=946234

[drew-parsons]

The relationship between cmake and setup.py seems to complicate the build conditions.

Joachim says the mere presence of cmake means it is invoked in pybuild build, https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=946233.

But it doesn't work that way for me. For me it's either dh --buildsystem=pybuild which does not invoke cmake, or dh --buildsystem=cmake, not clear what that does to the python build.

[nschloe]

This seems like it's related to pypa/setuptools#1732 (comment): setuptools indeed uses the C compiler, not C++, to compile C++ projects. Only the linker step uses CXX. Does it not on Debian?

[nschloe]

The relationship between cmake and setup.py seems to complicate the build conditions.

Hm. Well, the CMake files aren't terribly important to me, but sometimes I use them to debug which is why I don't want to toss them completely. If we can find another way of making this work, that'd be great.

[drew-parsons]

If we're clear on the intended role of cmake (intended for developer debugging only) then Debian can just ignore it. Perhaps a comment could be added to CMakeLists.txt or README to make that clear

The failing CGAL 5 build is documented at https://buildd.debian.org/status/package.php?p=pygalmesh
x86_64-linux-gnu-gcc is used for the linking step. This is with python3.8, so it could be possible that setuptools needs to be updated for the python3.8 context.

[nschloe]

Fixing this right now.

[nschloe]

Alright, all done now.

[drew-parsons]

Thanks, will test.