Improving the usability of C libraries in Swift

147 pointsposted 15 days ago
by timsneath
(swift.org)

36 Comments

skrrtww

15 days ago

This is pretty great stuff, I knew about the raw interop features but had no idea what API Notes offered. Quite cool.

I can't help but feel that Swift will ultimately be the "slow and steady wins the race" safe language of the future. Swift steadily working "first" on both tooling and cohabitability with existing ecosystems is a huge boon for adoption. It understands what an ABI is! If I were doing a greenfield cross platform application I think Swift would be the first thing I reach for now.

The qualms I have with Swift are mostly some of the more recent complex language features that can make Swift code much harder to understand and read, as well as the brainpower required to use Swift concurrency. That and some performance concerns, though many of those seem like they may be solvable with optimizations in LLVM.

mpweiher

15 days ago

> ... some of the more recent complex language features

This isn't recent. The approach that Swift took had this path locked in from the start, the (d)evolution towards ever more spiraling complexity was inevitable from the initial choices.

And this is not 20/20 hindsight, a lot of people, including yours truly, were saying that fron the very start. As an example, take initialization:

2014:

https://blog.metaobject.com/2014/06/remove-features-for-grea...

The swift book has 16 rules and 14 pages just on object initialization. Chris replied in the comments: "the complexity is necessary for <feature we want> and thus simplicity must give way". My reply: "the <feature you want> is incompatible with simplicity and thus must give way".

2020:

called it!

https://blog.metaobject.com/2020/04/swift-initialization-swi...

---

Or the syntax:

https://blog.metaobject.com/2020/06/the-curious-case-of-swif...

→ Swift included all of Smalltalk's keyword message syntax as a special case of a special case of the method call syntax.

---

Rob Rix:

“Swift is a crescendo of special cases stopping just short of the general; the result is complexity in the semantics, complexity in the behaviour (i.e. bugs), and complexity in use (i.e. workarounds).”

https://www.quora.com/Which-features-overcomplicate-Swift-Wh...

pinnochio

15 days ago

I was excited and optimistic about transitioning to Swift in the Swift 3 days. By Swift 5 I was pining for Objective-C.

One of the arguments for switching to Swift was that it would be easier for new programmers. Now I think it's more of a barrier than Obj-C ever was.

mpweiher

15 days ago

I don't pine. I use.

Although more and more I am shifting to Objective-Smalltalk: https://objective.st

pinnochio

15 days ago

That's neat.

Unfortunately, in my place of work, going back to Obj-C isn't an option.

ben_w

14 days ago

> I was excited and optimistic about transitioning to Swift in the Swift 3 days. By Swift 5 I was pining for Objective-C.

Swift 5 isn't that bad (even if result builders felt like a weird hack to make SwiftUI possible and I dislike SwiftUI massively) but around that point the language has increasingly made me think "why did this happen when Java already existed?"

mpweiher

11 days ago

That was my thought from the beginning.

user

14 days ago

[deleted]

aaronbrethorst

15 days ago

It feels like the language designers have never met a feature or paradigm they didn't love and agree to include :-\

arcticbull

15 days ago

Yeah, Swift started out fairly clear and cohesive and now it's just a katamari of every language feature ever made by anyone plus a whole bunch of home-grown features too. I'm always mixed on this because in isolation the feature is neat and I like it, but the totality of Swift is becoming as overwhelming and inconsistent as C++.

Now some C functions which are indistinguishable from free Swift functions get named parameters, and you can switch on some enumerations from C, and some C objects are ref counted but other ones still need you to do it. It's going to be quite something to keep track of which library is which since there's no way to know apriori.

mpweiher

15 days ago

While it has gotten even worse, thinking it was clear and cohesive in the beginning is rose tinted nostalgia.

budgefrankly

15 days ago

Yeah, Swift looks like someone started trying to port a C# syntax onto an esoteric object-orientated C-dialect (similar to Vala and GObject) then at the last moment noticed Rust 1.0 had been released, tried to patch on some Rust features, and hit release before they were done.

It's quite deceptive. Rust seems initially hard to learn, but it's a small language, so you arrive at competency faster than you might think. Swift seems initially easy to learn, but is a broad language with lots of edge-cases, so you're never quite as competent as you think you are, or need to be

Pulcinella

14 days ago

Ehh I have been using Swift from the beginning and I disagree with you and the parent. Swift was "good" before the addition of property wrappers and the result builder syntax. That's when lots of the weird "features" started being bolted on.

Before that it just felt like what a modern OO language with reference and value types, type safety, some very light "not truly functional but nice to have" functional programming features, and readable, "normal", dot syntax would be like. The language was basically complete at that point for the purposes of writing UI apps with the existing Apple frameworks.

zozbot234

15 days ago

> It understands what an ABI is!

Rust understands the C ABI, and that's plenty good enough for now. It's hard to guarantee safety anyway when you're linking to what's effectively outside code (not part of the same build) because we don't really have a fully typed equivalent for raw assembly or binary output (unlike your "safe" VM's, where the bytecode always undergoes sanity checks prior to execution) - hence why the raw C ABI often suffices in a practical sense.

pjmlp

15 days ago

That is surely the target for Apple platforms, whatever happens outside is more a nice to have kind of thing.

As proven by the track record of all languages that want to be simple, created as kind of anti-trends, they always tend to evolve into complexity as their userbase grows, as it turns out other programming language didn't got complex just for fun.

Then since they were initially created as kind of anti-complexity movement, the added on features always have warts due to not wanting to break compatibility, and are only half way there.

C23 versus PL/I, ALGOL variants, Scheme R7RS (full report) vs Lisp evolution, Java 26 vs Modula-3/Eiffel, Go 1.26 versus everyone, ...

pharaohgeek

15 days ago

I absolutely love Swift. I find it to be such an elegant language. I've done a few macOS/iOS apps with it over the years, but have really come to love it on the server. There are a couple of areas I feel could use some improvement with respect to cross-platform support, but overall the use of frameworks like Vapor have been a breeze to work with.

More support for language interoperability like this will just enhance the cross-platform experience. The Java ecosystem is what makes it so attractive to enterprises. Swift being able to easily take advantage of open-source C/C++ libraries will help with the migration.

andeee23

15 days ago

i’m not sure about the work on tooling

just a few weeks ago i was trying to work on a swift project in neovim and found the whole langserver experience pretty bad

and it’s way worse when working on swif ui apps, but i guess that’s more of an apple wanting you to use xcode thing.

i wish there was better tooling, i like the language, but i just switched to nim for my side project

pentamassiv

15 days ago

I find the Swift tooling very lacking. There's no way to lint dead code, there no way to auto format the files exactly as Xcode would do it and tell the linter those rules so that it doesn't lint your auto formatted code. Xcode project files are impossible to edit except with Xcode and Xcode often has issues and I need to manually empty the build folder. These are just some of the issues I remember

pharaohgeek

15 days ago

I do miss JetBrains' AppCode and their support for Swift in CLion. I wish they would open-source those plugins so that they can continue to be used in modern versions of CLion.

worldsavior

15 days ago

All the benefits you mentioned are trivial, as in- many languages have them already.

w10-1

15 days ago

I believe Apple is investing in C/C++ interop so much because they realize they'll likely keep their existing low-level system+embedded code rather than port it to Swift. That's good for people who want to do the same. A swift API layer can reduce the need for C/C++ developers.

But in my experience, there are sharp cliffs whenever you get off the happy path shown in the demos. That's not a problem with code where you can design workarounds, but when you wrap highly complex (if not arcane) C API, you often can't change or omit portions of the API causing problems. So while usability may be better, apinotes might not be enough to complete the work.

If you're wrapping something, I would recommend cataloging and then verifying all the language features you need to make it work before getting too far in.

dagmx

15 days ago

> so much because they realize they'll likely keep their existing low-level system+embedded code rather than port it to Swift

I disagree. I think it’s more that it reduces the burden to port to swift. Of course there’s some stuff you’ll never be able to port because of external factors, but reducing the burden to introduce a language is the first step in allowing more stuff to be shifted to that language transparently.

nicoburns

15 days ago

Yep. They also have a history of strong C/C++ interop with objective-c being based on C and objective-c++ (which allows compiling C++ and objective-c in one code file) also being a thing. I bet part of this is a good migration path for code (Apple and 3rd party) that uses that.

gregoriol

15 days ago

Sure they will keep C/C++, and various low-level code: Swift is nice for developers but slow for execution (compared tose).

handstitched

15 days ago

This was a great read. I've used the naive approach shown in the first example before and its always felt a bit clunky, but I wasnt aware of most of these language features. I'm definitely going to try this out next time I have to write C bindings

krzat

15 days ago

I love shitting on Apple's developer tools but they handled cross language integration really well.

Swift Package Manager handles Swift, ObjC, C, C++ in the same project, code completion works just fine. Overall much nicer than in other ecosystems.

waffletower

14 days ago

I don't find Swift to be an ergonomic systems language at all. I changed career paths soon after its introduction, focussing quite a bit on Clojure (and now begrudgingly Python) as I did not find value in its "safety" and much prefer ObjC's closeness to Posix and CoreFoundation libraries in the Apple ecosystem. Objective-C is bare bones and awkward indeed, but much more facile in interacting with system libraries. the typing dances required to utilize Swift in this low level context was absurd. I would probably investigate Zig first, and Rust second and even C++ long before Swift.

isodev

15 days ago

It's good to have options. I guess this is similar effort as Swift's java interop - created to enable internal Apple needs and a cool feature to share on socials for engagement. I don't think any of this would attract people who aren't already forced to use Swift. Generally, Apple's open source/public efforts feel more like a thing they do so they can point at this during antitrust/gatekeeper lawsuits than actual healthy foss ecosystem. (which is not a surprise of course, Apple is the opposite of foss).

secretsatan

15 days ago

I wish I'd known about adding the module.modulemap file, I found out about it some time last year while making a bunch of internal libraries compatible with Swift, it works with binary frameworks too.

I'd written considerable amounts of Objective-c bridging code before that.

randomNumber7

15 days ago

I think Swift has great C interop but they made pointers too diffcult to use. Which of the following type do you have to use if your C API returns some pointer?

UnsafeMutablePointer, UnsafePointer, UnsafeMutableBufferPointer, UnsafeBufferPointer, UnsafeMutableRawPointer, UnsafeRawPointer, UnsafeMutableRawBufferPointer, UnsafeRawBufferPointer

?? This is comical and the only reason to make it this clunky is because "unsafe is bad" and you don't want people to use it.

zffr

15 days ago

You listed 8 types, and this is because there are 3 axes that each have 2 values

- Mutable or not

- Typed or Raw

- Single object, or Buffer

Given one kind of pointer, you can convert to any other kind of pointer, but you are responsible for knowing if it’s safe to do.

The API is not super intuitive, but I can see how it makes it more clear what you are doing in your code.

dagmx

15 days ago

Your question as stated is exactly why there are so many pointer types.

Is it a pointer to raw memory or a pointer to a type? Does it have a known size? Should it be allowed to be changed?

These are all questions you have to answer in C but cannot without annotations or documentation. Languages with more expressive type systems need to map that ambiguity to something.

pyrolistical

14 days ago

Ah yes. The c abi, the thing that glues all cross lang function calls.

The human race will go extinct with the c abi still as the defacto standard at this point.

IMO any new system programming lang needs to compete over the quality of their c abi integration.

I still haven’t found a better c abi integration than zig. It can describe c funcs with higher precision than c itself.