At initialization, the subengine recursively iterates over the contents of its lib/ directory (in the root folder of the subengine) and loads each .so file.

You can use the fact that the iteration is recursive to organize your libraries into subdirectories as necessary. The subengine ignores files that do not end in .so.

The engine also expects to find a symbol called init in each of those shared objects. In pure C, this must be a function with signature:

V2_EXPORT void init( v2_context_t ctx ) { ... }

The signatures of the init function use the V2_EXPORT macro to ensure that the symbol is visible from the engine executable.

The main role of the init function is to tell the engine about the operators implemented by this library. Thus, this function is called once when the engine starts running, before its subgraph is even received.