New to Rust: How does Rust handle dynamic libraries
New to Rust: How does Rust handle dynamic libraries
I'm super new to Rust, like a day old really.
But I tried a program made in Rust on Windows, and it refuses to work.
Never prints anything. Just straight up instantly dead. Long story short, this thing relies on some linked stuff like ffmpeg in some form. So, I did my best trying to gather all the things it needs per github issues, reddit and other souces. And the end result was that it now spent 0.1 s longer before crashing, actually leaving time for some error in the Windows Event log. Nothing useful there either as far as I can see.
So I clone the repo and get the required things to compile Rust, and I managed to build it from source at least. The executable doesn't run, but the Run in VS Code works, somehow. It prints the error messages corresponding to missing input. So i try to debug it, but nothing happens. No breakpoint is hit, and nothing is printed in the terminal, unlike when using Run or cargo Run. I can also just strip out everything it does in the file the main function is in, and it will hit breakpoints. But that didn't help me find out what is missing/broken though.
So what the difference, is there a way to catch and prevent Rust from just going silent, and actually tell you what dependencies it failed to load?
My entire reason for getting it running locally is to fix that. Because no one sane wants to deal with a program that doesn't tell you why it will not run... And when debugging also does nothing... I'm out of ideas.
The program is called Av1an for reference, and it's a video encoding tool. I used a python version before they migrated to Rust, and wanted to give it a try again.
Edit: Wrote linked library, but i think the proper term is dynamic libraries. I'm really not good with compiled programs.
Update: Figured it out. Had to copy the out files from the ffmpeg compiled stuff back to the executable. Apparently Cargo Run includes that location when looing for the files, while running from the command line clearly doesn't.
But the biggest whiplash, was that I got a full windows dialog popup when i tried to in the exectuable in CMD instead of Powershell. Told me the exact file I was missing too. I know PowerShell is a bitch when piping stuff, but I'm amazed no other program or error message could hand me that vital information. Fuck me, I wish I had tried that from the start....
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Dynamic libs in rust are supported but only through a c abi and it's a bit complicated.
Looking at av1an I couldn't see anything showing it is dynamicly loading anything, it looks to statically link to ffmpeg according to the build instructions.
Thanks you for looking into it, if they are statically linked can something be done about it? Aka, same as other case, how do you detect missing required library to actually throw an error?
The issues where I learned most of it is here: https://github.com/master-of-zen/Av1an/issues/676
Having to build and find a ton of dlls is cumbersome. While I'm fairly sure I'm missing some ffmpeg ones, I'm somewhat taken aback by how running it with cargo run works just fine. But trying to run the very same executable built doesn't. And debugging also doesn't do anything. That doesn't make much sense to me, since the access to said dlls should be the same either way?? Either none of them works, or both does. Or there is some big difference between Cargo Run and the compiled executive when it comes to static or dynamic dlls loading.
OK so looking at that PR the reason you aren't getting any errors is because it looks like one of the dependencies is trying to load python and thats where the error occurs. Rust would normally give you a pretty good stack trace but because this is happening in external code it can't and you won't fix it in the av1an codebase. vscode likely has its path setup differently allowing it to find python. I would double check the paths inside the vscode terminal and wherever you are running it.
It's definitely a clue, but I got both system wide python, and a embedded one hooked up to vapoursynth (another dependency). Still doesn't explain why debugger doesn't work but running it does. As far as I see it, they should be the same.
Not sure if there is a solution, but I'm somewhat perplexed that the top level program can't handle crashes for a dependency it is either trying to load or use.
Thanks for the effort however, much appreciated.