8 ms·

> Swift will also let you do everything Rust can, very low level stuff. Not quite. Swift requires a runtime, so you probably won't see people writing OS kernel

by nardi 10y ago

> Swift will also let you do everything Rust can, very low level stuff. Not quite. Swift requires a runtime, so you probably won't see people writing OS kernels in Swift.

31reasons 10y ago
Swift uses LLVM as backend, so as far as I understand it can generate standalone binaries. No ?
- kibwen 10y ago
  Generating standalone binaries is orthogonal to the presence of a runtime. Go also generates standalone binaries (even more standalone than Rust and Swift) though it indisputably has a runtime.
- grayrest 10y ago
  All languages add a bit of code to a binary to make the code you write runnable. Rust [1] and C add almost none, language like Swift and Go have to add their GC support code even if it's in the same binary, and jit+scripting languages generally come with an external runtime. [1] https://www.rust-lang.org/faq.html#does-rust-have-a-runtime https://www.rust-lang.org/faq.html#does-rust-have-a-runtime (also mentions what's in the C runtime)
  - autoreleasepool 10y ago
    Swift doesn't have a GC and you can use it to program like C with malloc and free via UnsafeMutablePointer<T>. IIRC, Swift's runtime is like C++'s with v-table lookup for dispatch on functions that do not involve Objective-C objects.
    - kibwen 10y ago
      Swift's GC is in the form of pervasive reference counting for reference types with no automatic cycle detection. Though as we're demonstrating, calling this GC is contentious, it would be better if people weren't too lazy to type out "pervasive reference counting for reference types with no automatic cycle detection". :P (For the record, I believe Chris Lattner is on the record as saying "yes, Swift has a runtime, let's not bother arguing that point" though I can't find the link, but I agree that Swift's runtime is less invasive than most other languages (e.g. Go).)
      - joewillsher 10y ago
        Does saying 'ARC' not work for you? :) And the Swift runtime is pretty minimal, mostly used for storing dynamic type information, dispatching protocol methods, generating (unspecialised) generic types, checking conformances etc. It's mostly used by the compiler to add the dynamic features of the language; for example, the compiler observes the lifetimes of variables and inserts retain/release instructions, which are lowered down to a swift_retain or swift_release calls on the runtime instance. These functions are implemented in the runtime and do the manipulation of reference counts and deallocation.
        chc 10y ago
        I can see how you'd say that's minimal compared to languages with really huge runtimes — but do you really think it's minimal compared to C or Rust?
        Someone 10y ago
        It is simpler than a full GC, but I would not call that "pretty minimal". In particular, weak and unowned references and the guarantee that referencing them after the object they referred to was deallocated crashes your program make swift_release nontrivial.
    - joewillsher 10y ago
      Yes, the swift runtime does stuff like heap allocation & reference counting for classes, type introspection (including `as` casts), error handling, as well as generating instances of unspecialised generic types, and dispatching (dynamic) protocol methods (and other witnesses, like computed properties). https://github.com/apple/swift/tree/master/stdlib/public/runtime https://github.com/apple/swift/tree/master/stdlib/public/run...
pjmlp 10y ago
> Swift is a successor to both the C and Objective-C languages. Source: https://developer.apple.com/swift/ https://developer.apple.com/swift/
- nardi 10y ago
  Objective-C requires a runtime, and the Darwin kernel is not implemented in Objective-C. Also, Swift, unlike Objective-C, is not a superset of C.
  - deleted 10y ago
    [deleted]
  - pjmlp 10y ago
    Interesting that you decided to ignore the fact that Apple also mentions C, which is what the Darwin kernel is implemented on, isn't so? Which also happens to have a runtime, crt0.o.
    - the_why_of_y 10y ago
      C has a runtime, used in a "hosted" implementation (your typical *NIX user-space program) - but it's optional, and there is the alternative "freestanding" implementation that doesn't need to have a runtime or standard library, and this is generally used to implement kernels. http://www.iso-9899.info/n1570.html#4.p6 http://www.iso-9899.info/n1570.html#4.p6
      - pjmlp 10y ago
        Doesn't invalidate the fact that Swift could eventually be used in similar scenarios. Usually in these scenarios I believe it just requires a company to bully developers to accept it and an eventual generation change. If tomorrow Apple decides, for whatever reason, that new kext or IOKit modules are to be written in Swift, then whoever cares about their Apple OS customers will just comply with it.

by nardi 10y ago

> Swift will also let you do everything Rust can, very low level stuff. Not quite. Swift requires a runtime, so you probably won't see people writing OS kernels in Swift.

31reasons 10y ago

Swift uses LLVM as backend, so as far as I understand it can generate standalone binaries. No ?

kibwen 10y ago
Generating standalone binaries is orthogonal to the presence of a runtime. Go also generates standalone binaries (even more standalone than Rust and Swift) though it indisputably has a runtime.
grayrest 10y ago
All languages add a bit of code to a binary to make the code you write runnable. Rust [1] and C add almost none, language like Swift and Go have to add their GC support code even if it's in the same binary, and jit+scripting languages generally come with an external runtime. [1] https://www.rust-lang.org/faq.html#does-rust-have-a-runtime https://www.rust-lang.org/faq.html#does-rust-have-a-runtime (also mentions what's in the C runtime)
- autoreleasepool 10y ago
  Swift doesn't have a GC and you can use it to program like C with malloc and free via UnsafeMutablePointer<T>. IIRC, Swift's runtime is like C++'s with v-table lookup for dispatch on functions that do not involve Objective-C objects.
  - kibwen 10y ago
    Swift's GC is in the form of pervasive reference counting for reference types with no automatic cycle detection. Though as we're demonstrating, calling this GC is contentious, it would be better if people weren't too lazy to type out "pervasive reference counting for reference types with no automatic cycle detection". :P (For the record, I believe Chris Lattner is on the record as saying "yes, Swift has a runtime, let's not bother arguing that point" though I can't find the link, but I agree that Swift's runtime is less invasive than most other languages (e.g. Go).)
    - joewillsher 10y ago
      Does saying 'ARC' not work for you? :) And the Swift runtime is pretty minimal, mostly used for storing dynamic type information, dispatching protocol methods, generating (unspecialised) generic types, checking conformances etc. It's mostly used by the compiler to add the dynamic features of the language; for example, the compiler observes the lifetimes of variables and inserts retain/release instructions, which are lowered down to a swift_retain or swift_release calls on the runtime instance. These functions are implemented in the runtime and do the manipulation of reference counts and deallocation.
      - chc 10y ago
        I can see how you'd say that's minimal compared to languages with really huge runtimes — but do you really think it's minimal compared to C or Rust?
      - Someone 10y ago
        It is simpler than a full GC, but I would not call that "pretty minimal". In particular, weak and unowned references and the guarantee that referencing them after the object they referred to was deallocated crashes your program make swift_release nontrivial.
  - joewillsher 10y ago
    Yes, the swift runtime does stuff like heap allocation & reference counting for classes, type introspection (including `as` casts), error handling, as well as generating instances of unspecialised generic types, and dispatching (dynamic) protocol methods (and other witnesses, like computed properties). https://github.com/apple/swift/tree/master/stdlib/public/runtime https://github.com/apple/swift/tree/master/stdlib/public/run...

pjmlp 10y ago

> Swift is a successor to both the C and Objective-C languages. Source: https://developer.apple.com/swift/ https://developer.apple.com/swift/

nardi 10y ago
Objective-C requires a runtime, and the Darwin kernel is not implemented in Objective-C. Also, Swift, unlike Objective-C, is not a superset of C.
- deleted 10y ago
  [deleted]
- pjmlp 10y ago
  Interesting that you decided to ignore the fact that Apple also mentions C, which is what the Darwin kernel is implemented on, isn't so? Which also happens to have a runtime, crt0.o.
  - the_why_of_y 10y ago
    C has a runtime, used in a "hosted" implementation (your typical *NIX user-space program) - but it's optional, and there is the alternative "freestanding" implementation that doesn't need to have a runtime or standard library, and this is generally used to implement kernels. http://www.iso-9899.info/n1570.html#4.p6 http://www.iso-9899.info/n1570.html#4.p6
    - pjmlp 10y ago
      Doesn't invalidate the fact that Swift could eventually be used in similar scenarios. Usually in these scenarios I believe it just requires a company to bully developers to accept it and an eventual generation change. If tomorrow Apple decides, for whatever reason, that new kext or IOKit modules are to be written in Swift, then whoever cares about their Apple OS customers will just comply with it.