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I have a C++ app where I'm trying to use pybind11 in order to support a scripting system in my app that would allow users to write their own scripts. I'm attempting to use Python in much the same way that many people use Lua as a scripting language to extend their app's functionality.

There is one big difference I've found in regards to Lua vs Python/pybind11: with Lua I can statically link the scripting language into my executable or even package a single shared library, but with Python/pybind11 it seems that I am reliant on whether or not the end user has Python already installed on their system.

Is that correct?

Is there a way I can tell pybind11 to statically link the Python libraries?

It also seems that pybind11 will search the path for the python executable, and then assume the shared libraries are in the same folder. Is there a way I can distribute the shared libraries and then tell my embedded interpreter to use those shared libraries?

My ultimate goal is that users can install my C++ app on their machine, and my app will have a built-in Python interpreter that can execute the scripts, regardless if Python is actually installed on the machine. Ideally I would do this with static linking, but dynamically linking and distributing the required libraries is also acceptable.

Addy
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1 Answers1

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  1. Pybind11 does not search for Python executable or anything like that. You link against libpythonX.Y.so.Z, and it works just like with any other shared library. So you can link against your Python library that you distribute. You only need to make sure your executable will find your library at run time. Again, this is no different from distributing any other shared library. Use rpath, or use LD_LIBRARY_PATH in a wrapper script, or whatever. There is a ton of questions and answers about it right here on SO (first hit).

  2. You can link a static Python library, if you have one that is usable. On my system (Ubuntu 20 x64), trying to link against libpython3.8.a produces a ton of relocation errors. The system library only works when the entire executable is built statically, i.e. with g++ -static ... If you need a dynamic executable, you need to build your own static Python library with -fPIC. For the record, here is the command I used to link against the system library.

     g++ -static -pthread -I/usr/include/python3.8 example.cpp -lpython3.8 --ldl -lutil -lexpat -lz

  3. Last but not least, if your users want to write Python scripts, they probably have Python installed.

n. m. could be an AI
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