Create a `aarch64-apple-ios-sim` target for `rustc`

[deg4uss3r]

Currently in our application we cannot run the iOS simulator on M1 machines because it is expecting x86_64 architecture. Forcing arm64 using the rustc target aarch64-apple-ios can build the project and ship the application but this targets the iOS Device SDK, and will not build in the simulator for testing with this error:

ld: <path/to/lib> building for iOS Simulator, but linking in object file built for iOS, for architecture arm64

rustc should provide an aarch-apple-ios-sim target that uses the iOS Simulator SDK.

[shepmaster]

Is #77484 relevant at all? Can the same path be followed?

[deg4uss3r]

Awesome find @shepmaster I'll try doing this! If successful I'll open a similar PR :)

[badboy]

Ran into this now too. Happy to help here as well.
@deg4uss3r Did you already get started?

[deg4uss3r]

@badboy I did but having trouble I've pushed my changes here: https://github.com/deg4uss3r/rust/tree/degausser/aarch64_apple_ios_sim

More than happy to work with you on this Jan!

[badboy]

I'll try to get a dev environment set up and then I'll take a look.

[deg4uss3r]

I built the toolchain successfully, but when I try to compile my project (with either aarch64-apple-darwin or aarch64-apple-ios-sim) I'm getting:

error[E0277]: cannot subtract `usize` from `u32`
    --> $CARGO_REGISTRY_PATH/lexical-core-0.7.4/src/atof/algorithm/math.rs:2065:25
     |
2065 |     let rs = Limb::BITS - s;
     |                         ^ no implementation for `u32 - usize`
     |
     = help: the trait `Sub<usize>` is not implemented for `u32`

I think I've missed a setting in the build config I'm using, because the normal nightly compiles fine :(

config.toml: https://gist.github.com/deg4uss3r/183ef399590f74353691b21badc382cc

Edit looks like I will try off beta: #81654

[badboy]

Yeah, that looks like upstream breakage in lexical-core because of recent changes.
I can try taking your code tomorrow and throw this against my project to see if that fixes my simulator issues.

[deg4uss3r]

Yeah I added the patch mentioned in that issue and am getting further but:

ld: warning: ignoring file /Users/rth/work/core/target/aarch64-apple-ios-sim/debug/core.a, building for iOS Simulator-x86_64 but attempting to link with file built for unknown-arm64

which Xcode still seems to be getting x86_64 somewhere:

 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -target x86_64-apple-ios14.0-simulator 

I tried replacing all the x86_64 with arm64 and got closer:

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -target arm64-apple-ios14.0-simulator

but got:

ld: in /Users/rth/work/core/target/aarch64-apple-ios-sim/debug/core.a(sqlite3.o), building for iOS Simulator, but linking in object file built for iOS, for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

[deg4uss3r]

I believe my current version is working but there's something off in my Xcode project that I need to figure out:

❯ cargo build --target=aarch64-apple-ios-sim
   Compiling testing v0.1.0 (/Users/rth/code/experiments/testing)
    Finished dev [unoptimized + debuginfo] target(s) in 1.88s

❯ file testing
testing: Mach-O 64-bit executable arm64

target/aarch64-apple-ios-sim/debug on  master [?]
❯ ./testing
dyld: attempt to run simulator program outside simulator (DYLD_ROOT_PATH not set)
zsh: abort      ./testing

[badboy]

Ah, you're building a binary? Yeah, that seems to sort-of work now?
I managed to build your branch, my static library is still unchanged. I think we actually need LLVM 12 first to fully enable this (#81451).

[deg4uss3r]

It was just a test to see if the simulator is working at all XD.

Yeah my .a file is still saying it's arm64:

ld: in /Users/rth/work/core/target/aarch64-apple-ios-sim/debug/core.a(sqlite3.o), building for iOS Simulator, but linking in object file built for iOS, for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)