This made me quite curious, is there a list somewhere of what bad APIs have been removed/improved and/or technical debt that's been addressed? Or if not a list, some notable examples?
I don't know that there's a list, but cases come to mind because they've been controversial.
(Not a Linux hacker, so apologies if I get this wrong)
The filesystem APIs were quite arcane, and in particular whether or not you were allowed to call a C function at a certain point wasn't documented, and relied on experience to know already.
In trying to write idiomatic Rust bindings, the Rust for Linux group asked the filesystems maintainer if they could document these requirements, so that the Rust bindings could enforce as much of them as they could.
The Linux kernel is already very complex, and I expect that replacing much or all of it with Rust code will be good for making it more tractable to understand. Because you can represent complex states with more sophisticated types than in C, if nothing else.
I've been working on Rust bindings for a C SDK recently, and the Rust wrapper code was far more complex than the C code it wrapped. I ended up ceding and getting reasonable wrappers by limiting how it can be used, instead of moddeling the C API's full capabilities. There are certainly sound, reasonable models of memory ownership that are difficult or impossible to express with Rust's ownership model.
Sure, a different model that was easy to model would have been picked if we were initially using Rust, but we were not, and the existing model in C is what we need to wrap. Also, a more Rust-friendly model would have incured higher memory costs.
I totally hear you about C friendly APIs not making sense in rust. GTK struggles with this - I tried to make a native UI in rust a few months ago using gtk and it was horrible.
> Also, a more Rust-friendly model would have incured higher memory costs.
Can you give some details? This hasn’t been my experience.
I find in general rust’s ownership model pushes me toward designs where all my structs are in a strict tree, which is very efficient in memory since everything is packed in memory. In comparison, most C++ APIs I’ve used make a nest of objects with pointers going everywhere. And this style is less memory efficient, and less performant because of page faults.
C has access to a couple tricks safe rust is missing. But on the flip side, C’s lack of generics means lots of programs roll their own hash tables, array lists and various other tools. And they’re often either dynamically typed (and horribly inefficient as a result) or they do macro tricks with type parameters - and that’s ugly as sin. A lack of generics and monomorphization means C programs usually have slightly smaller binaries. But they often don’t run as fast. That’s often a bad trade on modern computers.
This is ultimately a good example of how to use Rust. You express as much of the API as you can safely, and the rest is unsafe. APIs that can't be safely modelled can still be exposed to Rust & marked unsafe, if they're needed
By most accounts the Rust4Linux project has made the kernel less complex by forcing some technical debt to be addressed and bad APIs to be improved.
This made me quite curious, is there a list somewhere of what bad APIs have been removed/improved and/or technical debt that's been addressed? Or if not a list, some notable examples?
I don't know that there's a list, but cases come to mind because they've been controversial.
(Not a Linux hacker, so apologies if I get this wrong)
The filesystem APIs were quite arcane, and in particular whether or not you were allowed to call a C function at a certain point wasn't documented, and relied on experience to know already.
In trying to write idiomatic Rust bindings, the Rust for Linux group asked the filesystems maintainer if they could document these requirements, so that the Rust bindings could enforce as much of them as they could.
The result was... drama.
The Linux kernel is already very complex, and I expect that replacing much or all of it with Rust code will be good for making it more tractable to understand. Because you can represent complex states with more sophisticated types than in C, if nothing else.
Complexity of Rust is just codifying existing complexity.
I've been working on Rust bindings for a C SDK recently, and the Rust wrapper code was far more complex than the C code it wrapped. I ended up ceding and getting reasonable wrappers by limiting how it can be used, instead of moddeling the C API's full capabilities. There are certainly sound, reasonable models of memory ownership that are difficult or impossible to express with Rust's ownership model.
Sure, a different model that was easy to model would have been picked if we were initially using Rust, but we were not, and the existing model in C is what we need to wrap. Also, a more Rust-friendly model would have incured higher memory costs.
I totally hear you about C friendly APIs not making sense in rust. GTK struggles with this - I tried to make a native UI in rust a few months ago using gtk and it was horrible.
> Also, a more Rust-friendly model would have incured higher memory costs.
Can you give some details? This hasn’t been my experience.
I find in general rust’s ownership model pushes me toward designs where all my structs are in a strict tree, which is very efficient in memory since everything is packed in memory. In comparison, most C++ APIs I’ve used make a nest of objects with pointers going everywhere. And this style is less memory efficient, and less performant because of page faults.
C has access to a couple tricks safe rust is missing. But on the flip side, C’s lack of generics means lots of programs roll their own hash tables, array lists and various other tools. And they’re often either dynamically typed (and horribly inefficient as a result) or they do macro tricks with type parameters - and that’s ugly as sin. A lack of generics and monomorphization means C programs usually have slightly smaller binaries. But they often don’t run as fast. That’s often a bad trade on modern computers.
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This is ultimately a good example of how to use Rust. You express as much of the API as you can safely, and the rest is unsafe. APIs that can't be safely modelled can still be exposed to Rust & marked unsafe, if they're needed
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Which SDK? I've only written Rust FFI to pretty basic C APIs. I'm curious to get a sense of the limitations on something more complex
There’s one already — they seem to be doing decently well.
https://www.redox-os.org/
No thanks, it's under MIT
How is that relevant to discussion about complexity?
Do you have any quantitative measures to prove there would be an increase in complexity?