paulyoung
February 25, 2023, 1:29am
#1
I managed to link and load a dynamic library when using the simulator on macOS:
opened 01:05AM - 25 Feb 23 UTC
tl; dr
It seems possible to use dynamically linked libraries with the simulat… or but I can't figure out how to modify the search paths.
Hopefully this is doable on device as well or this is all moot.
***
I'm depending on a crate that provides bindings for a library, and it expects the library to be dynamically linked.
At first I was getting `Undefined symbols for architecture` with `crank build`. I've addressed that with the following `build.rs`:
```rust
use std::{env, path::Path};
fn main() {
let cargo_manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
// This approach doesn't work because the library is named `foo_libqux.dylib`
/*
println!(
"cargo:rustc-link-search=all={}",
Path::new(&cargo_manifest_dir).join("lib").display()
);
println!("cargo:rustc-link-lib=dylib=retro");
*/
println!(
"cargo:rustc-link-arg={}",
Path::new(&cargo_manifest_dir).join("lib/foo_libqux.dylib").display()
);
}
```
However, `crank build --run` results in this error at runtime:
```
dlopen(/Users/py/projects/paulyoung/MyProject/main/target/My Project.pdx/pdex.dylib, 0x0006): Library not loaded: foo_libqux.dylib
Referenced from: /Users/py/projects/paulyoung/MyProject/main/target/My Project.pdx/pdex.dylib
Reason: tried: '/nix/store/g8b81w9kpb82gm7702ca692mp5flm7pf-apple-framework-CoreFoundation-11.0.0/Library/Frameworks/foo_libqux.dylib' (no such file), '/nix/store/g8b81w9kpb82gm7702ca692mp5flm7pf-apple-framework-CoreFoundation-11.0.0/Library/Frameworks/foo_libqux.dylib' (no such file), '/usr/lib/swift/foo_libqux.dylib' (no such file), '/Users/py/Developer/PlaydateSDK/bin/Playdate Simulator.app/Contents/MacOS/../Frameworks/foo_libqux.dylib' (no such file), '/Users/py/Developer/PlaydateSDK/bin/Playdate Simulator.app/Contents/MacOS/../Frameworks/foo_libqux.dylib' (no such file), '/usr/lib/swift/foo_libqux.dylib' (no such file), '/Users/py/Developer/PlaydateSDK/bin/Playdate Simulator.app/Contents/MacOS/../Frameworks/foo_libqux.dylib' (no such file), '/Users/py/Developer/PlaydateSDK/bin/Playdate Simulator.app/Contents/MacOS/../Frameworks/foo_libqux.dylib' (no such file), 'foo_libqux.dylib' (no such file), '/usr/local/lib/foo_libqux.dylib' (no such file), '/usr/lib/foo_libqux.dylib' (no such file), '//foo_libqux.dylib' (no such file), '/usr/local/lib/foo_libqux.dylib' (no such file), '/usr/lib/foo_libqux.dylib' (no such file)
```
<details>
<summary>(expand for a bulleted list of search paths)</summary>
<ul>
<li><code>/nix/store/g8b81w9kpb82gm7702ca692mp5flm7pf-apple-framework-CoreFoundation-11.0.0/Library/Frameworks/foo_libqux.dylib</code></li>
<li><code>/nix/store/g8b81w9kpb82gm7702ca692mp5flm7pf-apple-framework-CoreFoundation-11.0.0/Library/Frameworks/foo_libqux.dylib</code></li>
<li><code>/usr/lib/swift/foo_libqux.dylib</code></li>
<li><code>/Users/py/Developer/PlaydateSDK/bin/Playdate Simulator.app/Contents/MacOS/../Frameworks/foo_libqux.dylib</code></li>
<li><code>/Users/py/Developer/PlaydateSDK/bin/Playdate Simulator.app/Contents/MacOS/../Frameworks/foo_libqux.dylib</code></li>
<li><code>/usr/lib/swift/foo_libqux.dylib</code></li>
<li><code>/Users/py/Developer/PlaydateSDK/bin/Playdate Simulator.app/Contents/MacOS/../Frameworks/foo_libqux.dylib</code></li>
<li><code>/Users/py/Developer/PlaydateSDK/bin/Playdate Simulator.app/Contents/MacOS/../Frameworks/foo_libqux.dylib</code></li>
<li><code>foo_libqux.dylib</code></li>
<li><code>/usr/local/lib/foo_libqux.dylib</code></li>
<li><code>/usr/lib/foo_libqux.dylib</code></li>
<li><code>//foo_libqux.dylib</code></li>
<li><code>/usr/local/lib/foo_libqux.dylib</code></li>
<li><code>/usr/lib/foo_libqux.dylib</code></li>
</ul>
</details>
I've tried setting `LD_LIBRARY_PATH=./lib`, `DYLD_LIBRARY_PATH=./lib`, and `DYLD_FALLBACK_LIBRARY_PATH=./lib` when invoking `crank` but it doesn't make a difference to the search paths. I tried the same thing with `open -a "Playdate Simulator" ./target/My\ Project.pdx` but that didn't change anything either.
I also tried adding those environment variables via `cmd.env` in `run_pdc` and `run_simulator` in `main.rs` but still no change.
This obviously isn't a solution, but I copied the library and made it available at `~/Developer/PlaydateSDK/bin/Playdate Simulator.app/Contents/Frameworks/foo_libqux.dylib` and things appear to work.
It at least seems to demonstrate that this should work for the simulator as long as the search paths are set correctly. I don't have a device yet and I'm not sure where to begin on making this work there but hopefully there's nothing preventing this.
If I could get some insight or advice on how to go about this properly I'd be very grateful. Happy to make a PR to propose changes or document what I've found as a result.
I'm wondering if this is possible on devices. I don't have a device yet so I can't experiment.
I'm hoping someone could provide some insight on that so I can consider moving forward using the simulator for now and figure out static build later.
paulyoung
February 25, 2023, 1:38am
#2
I explained in the linked GitHub issue that I wasn't able to figure out how to modify the search paths for the simulator.
If anyone has any info on how to do that, I'd appreciate it.
samdze
February 25, 2023, 5:53pm
#3
As far as I remember FreeRTOS (the OS the Playdate runs) doesn't support dynamic linking, sadly.
1 Like
paulyoung
February 26, 2023, 5:14am
#4
Thanks. I didn’t know about FreeRTOS.
I found an old support thread from 2011 that says the same.
dave
February 27, 2023, 3:33am
#5
The current C API loader requires code to be compiled for a specific address, but we do have a new loader in the works that does relocation. I think that's all we'll need in order to support dynamic libraries on the device, but no promises
2 Likes
paulyoung
February 27, 2023, 7:26am
#6
Thanks, thats good to know!
Creating a static library looks more promising than I first thought in this case, but still a non-zero amount of effort.
Dynamic library support would be good in general.
paulyoung
March 4, 2023, 3:35am
#7
