pydip built from source fails to import

[anntzer]

Component pydip

Describe the bug Building pydip from source results in a library that fails to import

To Reproduce

$ mkdir build && cd build && cmake .. && make && make pip_install && python -c 'import diplib'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/some/prefix/lib/python3.10/site-packages/diplib/__init__.py", line 52, in <module>
    from .PyDIP_bin import *
ImportError: dynamic module does not define module export function (PyInit_PyDIP_bin)

Dumping the exported symbols from PyDIP_bin (nm -gD PyDIP_bin.cpython-310-x86_64-linux-gnu.so) shows that that symbol is indeed absent.

System information:

• What OS do you have? fedora37
• If PyDIP, what version of Python do you have? python 3.10 from conda-forge; the entire compiler toolchain is from conda-forge too.
• If DIPimage, what version of MATLAB do you have? (type ver at the MATLAB command prompt, and copy-paste the result here).
• If compiled from sources, what compiler and version did you use? g++ (conda-forge gcc 12.2.0-19) 12.2.0

[crisluengo]

Thanks. Yes, I need to improve the documentation here.

You need to do make install before you do make pip_install. Otherwise the DIPlib libraries will not be found by the Python module.

Alternatively, you could set DIP_PYDIP_WHEEL_INCLUDE_LIBS to On in the CMake configuration step. In this case, the DIPlib libraries will be copied over into the installed wheel.

[anntzer]

I tried with cmake -DDIP_PYDIP_WHEEL_INCLUDE_LIBS=On .. and things fail with the same error. Haven't tried with make install as I'd rather not move stuff into /usr; is it possible to install into a prefix? Note, though, that the error ("ImportError: dynamic module does not define module export function (PyInit_PyDIP_bin)") suggests that the problem is not with finding diplib(?)

[crisluengo]

Yes, you can install into any prefix.

My working hypothesis is that the error message is inaccurate, that it cannot load the PyInit_PyDIP_bin module because some of its dependencies are missing.

It not working with the libraries included in the wheel is strange though. That might indicate some other issue. Check the Python version in thr CMake configuration output, and make sure it’s identical to the version of Python you’re trying to run this in. If not, configure in the CMake call the Python executable.

[anntzer]

CMakeCache.txt says e.g. that

//Path to a program.
PYTHON_EXECUTABLE:FILEPATH=/home/antony/miniconda3/envs/default/bin/python

//Path to a library.
PYTHON_LIBRARY:FILEPATH=/home/antony/miniconda3/envs/default/lib/libpython3.10.so

which is correct.

I'll continue investigating...

---

Followup: I get the same failure using both conda-python (eveything in a conda env) or distro(fedora)-python (everything out of conda) on linux. OTOH I did manage to get things to work on Windows, which is better than nothing and at least I can move on and investigate whether I can e.g. improve the situation wrt #125.

[crisluengo]

Closing this because it's been inactive for long. Please reopen if you ever learn more!