Build/install issue with shared libraries

[parthapn98]

Hi Im building april tag using the commands under install here https://github.com/AprilRobotics/apriltag

if i build for -DBUILD_SHARED_LIBS=OFF The install works properly, however i need the python wrapper for my work.

However when building with -DBUILD_SHARED_LIBS=ON followed by cmake --build build --target install --clean-first I get an error: LINK : fatal error LNK1104: cannot open file 'Debug\apriltagd.lib'

and the file itself is missing in the directory.

Any suggestions? Windows 10, python 3.9.13

[christian-rauch]

The python wrapper (BUILD_PYTHON_WRAPPER) can only be used with shared libraries (see cmake_dependent_option(BUILD_PYTHON_WRAPPER "Builds Python wrapper" ON BUILD_SHARED_LIBS OFF)).

At least on Linux, the wrapper is built automatically if BUILD_SHARED_LIBS is ON. I haven't tried this on Windows. The Python wrapper may just not work on Windows. I can review a PR if someone implements this with a CI pipeline.

[parthapn98]

is the build tested on unix/ redhat? it worked fine on Ubuntu

however in windows the build+install without the shared libraries work but with shared libraries they don't. can you recommend a way for me to share the data with you if you are willing to look into this?

[christian-rauch]

is the build tested on unix/ redhat? it worked fine on Ubuntu

I only ever use this on Ubuntu. I assume that this should work on any recent Linux distribution that provides the dependencies. I am not sure if you can compile this on any UNIX variant

however in windows the build+install without the shared libraries work but with shared libraries they don't. can you recommend a way for me to share the data with you if you are willing to look into this?

Sorry, I don't use Windows and I also do not want to invest the time to set up a Windows development environment in a VM.

The Windows support was generously provided (amongst others) by @ryancwicks (https://github.com/AprilRobotics/apriltag/pull/234) and @VincentMarnier (https://github.com/AprilRobotics/apriltag/pull/240). They may be able to help you.

[VincentMarnier]

Hello, I think I might misunderstand something here as I successfuly can build for windows (with and without cross compiling) with both DBUILD_SHARED_LIBS ON and OFF. I am using the "Developer Command Prompt for VS 2022" (with cmake installed by "Visual Studio Installer"). I run the following commands:

cmake -B build -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON
cmake --build build --config Release --target apriltag

I then have build/Release/apriltag.dll generated.

I tried the python build, installing python on my machine, but ended up on "python_build_flags.py" being called and raising an error. Looking at the file it seems like it just print some Make parameters so it is probably not useful for MSVC anyway. I never really used python so I doubt I will be of any help if you have to dig this way, sorry.

If this is of any help, here is what I did though:

• I installed python 3.11.0
• I used pip install numpy
• I replaced all the execute_process(COMMAND python3 [...]) by execute_process(COMMAND python [...]) because for some reason python3 was an issue (even outside of cmake env, using python3 --version was raising an error)
• Finally I tried the python build and faced an error when calling python_build_flags.py

I hope you will find your way. Cheers!

EDIT: The error:

Traceback (most recent call last):
  File "C:\Users\vince\Documents\apriltag\python_build_flags.py", line 21, in <module>
    print(conf.get('BLDSHARED', '').split()[0], end=';')
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^
IndexError: list index out of range

EDIT2: Btw, if I comment the execute_process(COMMAND python ${CMAKE_CURRENT_SOURCE_DIR}/python_build_flags.py OUTPUT_VARIABLE PY_OUT), then running cmake --build build --config Release --target apriltag_python generates a .dll file. I am not sure this is what you are expecting though as there is no python sources aside or anything. I might be wrong though as, again, I am not a python dev at all.

[parthapn98]

Hi @VincentMarnier

Thank you for the detailed post. Basics: i have python3.9 on windows and python3/ python are both bound to it and bypasses the same error you mentioned

the commands i run are

cmake -B build -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON
cmake --build build --target install

note. if target set to apriltag or different name the second command executes successfully, however then the default python wrapper as mentioned in https://github.com/AprilRobotics/apriltag/wiki/AprilTag-User-Guide#python is not installed

the output log for the corresponding commands are as attached build.txt install.txt

The logs are same(allowing for directory naming) if i build withing VStudio

Any idea what could be causing this to happen?

Note i donot get a call or error to python_build_flags.py

[christian-rauch]

Fixed via https://github.com/AprilRobotics/apriltag/pull/310.