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Xcode / Swift compatibility

The CryptoKit provider uses Swift under the hood and requires linking against Swift standard libraries shipped with Xcode. The published library embeds a hardcoded path to these libraries:

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/PLATFORM

This path is baked into the published cinterop klib and cannot be made dynamic at publish time. As a result, builds fail when Xcode is not located at /Applications/Xcode.app — a common situation when you:

  • manage multiple Xcode versions with tools like xcodes,
  • rename the Xcode bundle (e.g. Xcode_16.4.app), or
  • keep Xcode on a different volume or path.

Typical error:

Could not find or use auto-linked library 'swiftCompatibilityPacks'

Apply the dev.whyoleg.cryptography Gradle plugin in the module that uses CryptoKit. The plugin dynamically resolves the active Xcode installation at build time using xcrun, so it works regardless of where Xcode is installed.

In build.gradle.kts, apply the plugin and enable automatic linker option configuration:

plugins {
    id("dev.whyoleg.cryptography") version "0.6.0"
}

cryptography {
    configureSwiftLinkerOpts = true
}

The plugin will automatically add the correct -L linker flags for every Apple target binary in your project.

Manual linker options

If you cannot use the Gradle plugin, you can add the linker options manually.

Find your Swift libraries path by running the following command and replace /usr/bin/swift with /usr/lib/swift in the output:

xcrun --find swift
# example output:
# /Applications/Xcode_16.4.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift
# → use: .../XcodeDefault.xctoolchain/usr/lib/swift

Add the path to every Apple binary in your build.gradle.kts:

val swiftLibsPath =
    "/Applications/Xcode_16.4.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift"

kotlin {
    listOf(
        iosArm64(),
        iosSimulatorArm64(),
        iosX64(),
        macosArm64(),
        macosX64(),
        // add other Apple targets as needed
    ).forEach { appleTarget ->
        val platformDir = when (appleTarget.konanTarget) {
            KonanTarget.IOS_ARM64  -> "iphoneos"
            KonanTarget.IOS_SIMULATOR_ARM64,
            KonanTarget.IOS_X64
                                   -> "iphonesimulator"
            KonanTarget.MACOS_ARM64,
            KonanTarget.MACOS_X64
                                   -> "macosx"
            KonanTarget.TVOS_ARM64 -> "appletvos"
            KonanTarget.TVOS_SIMULATOR_ARM64,
            KonanTarget.TVOS_X64
                                   -> "appletvsimulator"
            KonanTarget.WATCHOS_ARM32,
            KonanTarget.WATCHOS_ARM64,
            KonanTarget.WATCHOS_DEVICE_ARM64
                                   -> "watchos"
            KonanTarget.WATCHOS_SIMULATOR_ARM64,
            KonanTarget.WATCHOS_X64
                                   -> "watchsimulator"
            else                   -> error("Unsupported Apple target: ${appleTarget.konanTarget}")
        }
        appleTarget.binaries.configureEach {
            linkerOpts("-L$swiftLibsPath/$platformDir")
        }
    }
}