Basic implementation of hot-loading/mods

[martinrlilja]

Addresses parts of #93.

What I've done:

• Implemented package format. Skipped dependencies.
• Loading of packages from disk.
• Loading of dylibs, registered from packages.
• Interfaces for mods to implement in order to be loaded.
• A tiny proof of concept mod.

How to use:

1. Run the game with cargo run.
2. If everything went well, you should see the text my mod was loaded! in the terminal.

What's missing:

• Only tested on Linux x86_64, and MacOS.
• Loading of whole directories of mods.
• Dependencies, and loads of other things.

This is just a first prototype though, but I wanted to put it up to get some feedback before I continue.

[Herbstein]

I'll test this on a Windows 10 64-bit laptop in the afternoon. Impressive work!

[aeplay]

Great work!

FYI: on Mac, everything compiles, but I get this error on startup, which I don't really understand:

dyld: Library not loaded: @rpath/librustc_metadata-b03b26491b91b850.dylib
  Referenced from: /Users/anselm/Dropbox (Personal)/Data/Projekte/cb/rust/target/release/citybound
  Reason: image not found

I can't find this librustc_metadata-b03b26491b91b850.dylib in target/release/deps and don't know where else it could be.

[martinrlilja]

@aeickhoff That's weird, could you try to remove extern crate rustc_metadata; from weaver/lib.rs?

Edit: I think that these objects come from ~/.rustup/toolchains/nightly.../lib/. Out of curiosity, what happens if you just import extern crate rustc_driver; and call rustc_driver::main(); somewhere and run that?

[chances]

Should be, "module is not a file ..."?

[martinrlilja]

Yup, fixed 😄

[aeplay]

Out of curiosity, what happens if you just import extern crate rustc_driver; and call rustc_driver::main(); somewhere and run that?

Tried that, got the same error as above.

[martinrlilja]

@aeickhoff Okay, I'm fairly certain that the error is because the library is not in your path. You should be able to verify it with otool on mac. So, try my latest version, run it with cargo run, it should correctly set the path to your rustup install. Otherwise you might have to set DYLD_LIBRARY_PATH.

[aeplay]

By setting DYLD_LIBRARY_PATH to the lib folder in my dustup install, it works indeed! (but crashes when quitting the application)

also, FYI: Mac doesn't recognise the -enable-new-dtags ld option

[martinrlilja]

That's great! I think I will make it so that the ld option only runs on *nix.

The crash on exit is a bit worrying, it might be either because of this: https://github.com/citybound/citybound/pull/95/files#diff-98e384c6f9803e1156e01ae31bb92c57R163 or because of this: nagisa/rust_libloading#5

[martinrlilja]

@chances Just to make it more obvious that we are talking about the root of everything. Kind of like URLs. We could also make it so that a single forward slash refers to the root of the current source.

It's definitely something we should discuss more to find something that works the best.

[aeplay]

Archiving this for now, I'll include you guys in discussion regarding the new mod-from-inside-the-game idea when it's time!