Adventures in Advent of Code

I guess the bug is apparently in the Swift runtime itself, and since Swift 5.0 and ABT stability, the runtime version is tied to the OS version.

https://www.swift.org/blog/abi-stability-and-apple/

But I think that only applies to deployments via the App Store. I think for local development you can run against the current runtime by setting the TOOLCHAINS environment variable (you may also need to set SDKROOT).

https://www.swift.org/getting-started/#on-macos

ETA. Apple does not make it easy to replace the runtime, but I got it to work like this:

    $ sw_vers
    ProductName: macOS
    ProductVersion: 12.6
    BuildVersion: 21G115
    
    $ cat foo.swift
    let a = "gnmCjzwnmCPTPhBwPjzBgqPjllJJSWlhfhQDSrpJRhDSlfJl"
    let b = "rLHNHrLHVNbVHMMctZFHsbcsDSDWpSDSGfSRsRWSRllfGSSG"
    let c = "NNtdMVrLNdZNvLvLZrzCndqBgwwPmwgjggBn"
    
    var s1 = Set(a)
    s1.formIntersection(b)
    s1.formIntersection(c)
    print(s1)
    
    var s2 = Set(a)
    s2.formIntersection(Set(b))
    s2.formIntersection(Set(c))
    print(s2)
    
    $ swiftc -version
    swift-driver version: 1.62.15 Apple Swift version 5.7.1 (swiftlang-5.7.1.135.3 clang-1400.0.29.51)
    Target: arm64-apple-macosx12.0
    
    $ swiftc foo.swift
    $ ./foo
    ["P", "r", "C", "z", "w", "m", "B", "q", "j", "g", "n"]
    ["r"]
    
    $ otool -L foo
    foo:
     /usr/lib/libobjc.A.dylib (compatibility version 1.0.0, current version 228.0.0)
     /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1319.0.0)
     /usr/lib/swift/libswiftCore.dylib (compatibility version 1.0.0, current version 
    $ DYLD_LIBRARY_PATH=/Library/Developer/Toolchains/swift-5.7.1-RELEASE.xctoolchain/usr/lib/swift/macosx ./foo
    ["r"]
    ["r"]

    $ /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -version
    Xcode 14.1
    Build version 14B47b
    $ DYLD_LIBRARY_PATH=/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/macosx ./foo
    ["B", "P", "q", "C", "r", "n", "j", "w", "m", "z", "g"]
    ["r"]

The dylibs under /Library/Developer/Toolchains/swift-5.7.1-RELEASE.xctoolchain/usr/lib/swift/macosx are arm64 and x86_64.

WTF Apple?

Most years I choose a language I've never worked with commercially (e.g. Fennel in 2022) and rather than reach for prebuilt libs for timesaving fancy array or set or string ops, I'll invent those wheels myself without dependencies and I find a ton of satisfaction in it. Unwise commercially but ideal for learning and play. And, yeah, bugs!

IMO, when it's not a customer paying for my learning curve, there's a lot to be said for rewalking old paths with new boots (or no boots and funky coloured glasses). Also, a terrible way to get onto the leaderboard IME!