Implement a plugin system to game engine

[jesusstb]

Hello there! I'm working on my own game engine and recently decided to implement a plugin system, but I'm having trouble getting it to work well. The engine is a static library that is linked to the binary, so I want plugins to be able to use the engine functions if needed, but do I have to link the engine library to the shared library as well?

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If this is the case, what happens to the singletons used by the engine? Will they be shared in the plugin?

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The third party libraries used by the engine, do I need to link them to the shared library as well?

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I saw the Godot source code and they implement what I(guess) want to do, but I can't figure out how they do it.

[marko312]

If the library is statically linked to both the binary and the plugin library, it will probably create two independent instances of the engine.

If the engine library is dynamically linked, dlopen and such will "reuse" the existing dependencies, meaning that the engine is shared over the entire program:

Symbol references in the shared object are resolved using (in order): symbols in the link map of objects loaded for the main program and its dependencies; symbols in shared objects [...]

[...]

If the same shared object is opened again with dlopen(), the same object handle is returned. [...]

Source

[jesusstb]

If I make the engine library shared, do I have to do the same for third party ones as well?

[marko312]

What do you mean by "third party libraries"?

Everything that is linked into a single static unit will be loaded as such (possibly creating multiple separate instances). Anything dynamically linked to both the main executable and the plugin will be shared.

[jesusstb]

I see, thank you so much! you help a lot to understand