Add minimal support to Zig toolchain to support building iOS binaries #9532
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* ensure we correctly transfer `-iwithsysroot` and `-iframeworkwithsysroot` flags with values from `build.zig` and that they are correctly transferred forward to `zig cc` * try to look for `libSystem.tbd` in the provided syslibroot - one caveat that the user will have to specify library search paths too
this makes the app successfully run on the iOS simluator!
For example, in order to run a binary on an iPhone Simulator, you need to specify that explicitly as part of the target as `aarch64-ios-simulator` rather than `aarch64-ios-gnu` or `aarch64-ios` for short.
This is now no longer limited to targeting macOS natively but also tries to detect the sysroot when targeting different Apple platforms from macOS; for instance targeting iPhone Simulator from macOS. In this case, Zig will try detecting the SDK path by invoking `xcrun --sdk iphonesimulator --show-sdk-path`, and if the command fails because the SDK doesn't exist (case when having CLT installed only) or not having either Xcode or CLT installed, we simply return null signaling that the user has to provide the sysroot themselves.
otherwise, linking may fail as some libc functions are provided by the host when simulating a different OS such iPhoneOS.
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This was referenced Aug 14, 2021
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With this change, it is possible to successfully target iOS and iPhone Simulator platforms. See kubkon/zig-ios-example for a complete project example how.
Major changes include:
-iwithsysrootand-iframeworkwithsysrootflags with values frombuild.zigand that they are correctly transferred forward tozig ccstd.zig.system.macosintostd.zig.system.darwin.macossince we now special-case all Apple platforms when building from another Apple platform (usually macOS) -std.zig.system.darwin.getSDKPathnow takes two args as input: allocator andTarget, and based on the target it will invokexcrun --sdk <sdk_name> --show-sdk-pathwith the appropriatesdk_namesuch asiphonesimulatororiphoneos, etc. With this change, we make Zig auto-invokegetSDKPathwhen targeting an Apple platform from an Apple platform, meaning that we no longer constrain ourselves to running natively but also when targetingiosfrommacos, etc.libSystem.tbdin the provided syslibroot.simulatorABI when targeting iOS -.simulatorABI signals that the binary is meant to be run on Apple iPhone Simulator rather than on a real device and therefore it should be linked against a completely standalone set of libraries and frameworks known asiphonesimulatorSDKVERSION_MINload command forBUILD_VERSION- turns out, the latter is required to make the app get properly launched on the iPhone Simulator, while presence of the former generates a sigkill-equivalent for some reasonI could use some input here on the validity of treating
std.build.addSystemIncludeDirandstd.build.addFrameworkDirdifferently based on the presence of the sysroot on the command line - if there is no sysroot present, we convert them into-isystemand-iframework; if the sysroot is present however, we change that to-iwithsysrootand-iframeworkwithsysroot. This can trigger a weird error if we are auto-detecting sysroots by Zig (when targeting iOS for instance) and the user adds explicit system search paths to theirbuild.zigas then we get conflicting search dirs for the headers which can lead to a compile error.UPDATE: turns out that when linking against simulator ABI such as
aarch64-ios-simulator, several libc functions such asfstat, etc., are provided by the host (aarch64-macos), and thus, it is necessary to take that into account when linking against tbd stubs. This has now been added in 83f1203.