Referencing third party libs

[rolandreichweinbmw]

Currently, external third party libraries are provided as copies under libs/3rdparty. This has the advantage of OpenBSW being relatively self-contained. Disadvantages are:

• Hard to track possible deviations (or proving absence of such) from upstream projects
• Copies need to be maintained actively, otherwise they are prone to bit-rot

For solving this, I'd propose a unified approach to handle all or at least most of libs/3rdparty with one of the following mechanisms:

• CMake: find_package, FetchContent, ExternalProject, etc.: CMake-specific, unfortunately - doesn't cover other build systems if necessary
• git submodules: depending on git, obviously
• Installing/requiring .deb packages via "apt install". This can be combined with version detection and compile/link options from FindPkgConfig or similar. E.g., ETL is available as a standard Debian package.

Ideally, we would use the same mechanism for all same party libraries.

[johannes-esr]

We discussed this internally, and in our opinion it would be better if all third-party modules are contained within the repository, to ensure consistency and that e.g. a build is also possible without internet connection. Of course, there can be extensions for special cases.

[rolandreichweinbmw]

LWIP in libs/3rdparty is currently tracked via "rim" in .riminfo . If we stick to the copying-in approach, an option would be to use rim systematically for all libs/3rdparty/*

[devcurmudgeon]

I think copying in code from dependencies is not really a good practice, because it means we lose traceability for upstream history of the dependency code, and we remove the possibility to track for upstream changes.

Given there is the intention to build community around openbsw and encourage more adoption, then I think it would be better sort out the dependency management properly :-)

[rolandreichweinbmw]

Rim seems to solve some of those issues. However my above list of alternative approaches for using external dependencies should be extended if possible and then discussed.

[devcurmudgeon]

It seems there are maybe 6 dependencies being handled like this already. For larger projects I would suggest BuildStream, which provides a mature solution for dependency management including local caching of sources. Not sure if it may be overkill for openbsw, but it could be added to the list of alternatives.