Building pyrealsense2 does not include librealsense

[oliverdain]

Camera Model: D415 (but also irrelevant)
FW Version: irrelevant
Operating System: Linux (Debian Bullseye) and OSX (Big Sur)
Platform: OSX and Debian Linux
Language: cmake

Issue Description

Intel doesn't provide a pre-build pyrealsense2 for OSX so I compiled my own. However, if I pip install the .whl file I built it is not statically linked against librealsense2 so users also have to install that. This is true on both OSX and Linux. However, I followed the instructions to compile everything and then ran python3.7 setup.py bdist_wheel to create the wheel file but somehow my version is different from the one built by Intel. For example, for the one I built if I run ldd on the pyrealsense2.cpython-37m-x86_64-linux-gnu.so that is included in the wheel I get:

        linux-vdso.so.1 (0x00007fffb6dec000)
        librealsense2.so.2.49 => not found
        libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f9767761000)
        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f976761d000)
        libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f9767603000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f976743e000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f9767d68000)

but if I download the official Linux one and run ldd I get:

        linux-vdso.so.1 (0x00007ffebd9f1000)
        libusb-1.0.so.0 => /lib/x86_64-linux-gnu/libusb-1.0.so.0 (0x00007fb2f3ca0000)
        libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fb2f3ad3000)
        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fb2f398f000)
        libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fb2f3975000)
        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fb2f3953000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fb2f378e000)
        /lib64/ld-linux-x86-64.so.2 (0x00007fb2f53bc000)
        libudev.so.1 => /lib/x86_64-linux-gnu/libudev.so.1 (0x00007fb2f3764000)

so the official one does not need to be dynamically linked against librealsense2.so.2.49. I suspect the instructions just need to be updated.

To be clear, here's the steps I followed:

1. Run cmake with -DBUILD_PYTHON_BINDINGS:bool=true and '-DPython_ADDITIONAL_VERSIONS=3.7'.
2. Run make -j4 pyrealsense2 pybackend2
3. Copy pybackend2.cpython-37m-x86_64-linux-gnu.so and pyrealsense2.cpython-37m-x86_64-linux-gnu.so into wrappers/python/pyrealsense2
4. Run the find_librs_version.py script
5. Run python3.7 setup.py bdist_wheel

I imagine I need some extra cmake flag to have my pyrealsense2.cpython-37m-x86_64-linux-gnu.so statically linked against librealsense2 but I don't see an obvious flag and it's not documented.

Note that the main reason I'm doing this is that there isn't an OSX version so I need to compile that. I only repeated the steps on Linux so I could compare to the official pyrealsense2 wheel provided by Intel.

[oliverdain]

Also note that copying librealsense2 to wrappers/python/pyrealsense2 causes it to be in the wheel file but it's still not found as ldd doesn't know where to look for it.

[MartyG-RealSense]

Hi @oliverdain A RealSense user recently created an automated process at #9687 for installing pyrealsense2 on MacOS that can create pre-built wheel files. Comparing it to your own method may provide useful insights.

[oliverdain]

Thanks for the pointer @MartyG-RealSense . I took a look at his code and he's bundling librealsense and then using delocate after the wheel is built to update the rpath. That works but seems really hacky and I suspect it's not how you build the official wheels you release (particularly since delocate is OSX only). I was hoping there's a cleaner way to do it.

[MartyG-RealSense]

The Python wrapper documentation states that the PyPi (pip install) wheel files for x86 / x64 are generated from the Python wrapper folder with the command python setup.py bdist_wheel

https://github.com/IntelRealSense/librealsense/tree/master/wrappers/python

[oliverdain]

Thanks @MartyG-RealSense . As noted that is what I'm doing. And I can get a working wheel file, but one that relies on librealsense2.49 having been installed system wide which means a simple pip install doesn't give you a usable system. Furthermore, Intel's own .whl files do not have a dependency on an external librealsense so it seems it's possible to create a stand-alone pyrealsense2. However following the official instructions, including the setup.py bdist_wheel step you recommend, produces a .whl with a dependency on an external librealsense. So, apparently, those are the instructions that Intel follows to produce the wheel's it releases to PyPi. Similarly, the link you sent me to the OSX wheel has a few hacks to modify the .whl after it's been built. What I'd like to know is how to produce a wheel without a dependency on an already installed librealsese. If you could point me to a link or some information on how Intel produces the wheel's that it releases to PyPi that should suffice.

[MartyG-RealSense]

I researched your question carefully but it is admittedly one that is outside of my Python installation knowledge. If you would like to explore deeper into the subject of wheel file creation, there is a highly technical discussion at #8229

Within that discussion, a RealSense user suggested downloading an existing wheel file and then editing its binary with a hex editor tool.

#8229 (comment)

The downloads page for the official wheels is here:

https://pypi.org/project/pyrealsense2/#files

[oliverdain]

Hi @MartyG-RealSense . Thanks for the update. I'm afraid that link doesn't help: it's about how to modify the metadata in a wheel to declare that it's compatible with Python 3.9 which isn't my situation at all.

Clearly somebody at Intel has a process for building a wheel file such that it does not depend on an externally install librealsense2: that's what you release to PyPi. I'd expect that you also have that series of steps running automatically on your CI/CD. Could the person who knows how to do it maybe chime in with the magic missing step?

[MartyG-RealSense]

@Nir-Az Would it be possible to offer advice to @oliverdain regarding their question above please? Thanks!

[Nir-Az]

Hi,
If you wish to build pyrealsense to be self contained you need to add the following CMake flag to the CMake configure step.

-DBUILD_SHARED_LIBS=false

This way you get a statically linked binary file.
Let us know if it did the trick 😉

[oliverdain]

That did the trick @Nir-Az . Thank you!

I suggest updating the documentation; it was definitely not obvious to me how to do this.

[MartyG-RealSense]

@Nir-Az Thanks very much for your always excellent help on the subject of Python wheels!

@oliverdain Great to hear that the advice of @Nir-Az was successful for you :)

[Nir-Az]

@oliverdain Thanks for alerting about the missing documentation.
The python wrapper readme file has been updated! #9781