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Merged
keith merged 2 commits into from
Jul 6, 2026
Merged

Link libdispatch for Swift Concurrency on Android #1830

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a761043
Link libdispatch for Swift Concurrency on Android
AttilaTheFun Jul 6, 2026
76624ff
android example: exercise Swift Concurrency
AttilaTheFun Jul 6, 2026
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9 changes: 9 additions & 0 deletions examples/cross_compilation/android_app/Sources/Greeter/Greeter.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -8,4 +8,13 @@ public struct Greeter {
public func greeting() -> String {
return "Hello from Swift, \(subject)!"
}

// Swift Concurrency: async code pulls in the concurrency runtime, whose
// global executor lives on libdispatch. This exists so the example is a
// link-time regression test for the `-ldispatch -lBlocksRuntime` linkopts
// in the generated Android toolchain — without them, linking any `async`
// Swift fails with `undefined symbol: dispatch_main` (and friends).
public func greetingAsync() async -> String {
return greeting()
}
}
5 changes: 5 additions & 0 deletions examples/cross_compilation/android_app/Sources/SwiftJNI/SwiftJNI.swift
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Expand Up @@ -6,6 +6,11 @@ import Greeter
// symbol name that `NativeBridge.greetingFromSwift()` binds to.
@_cdecl("Java_com_example_swiftjni_NativeBridge_greetingFromSwift")
public func greetingFromSwift(_ env: UnsafeMutablePointer<JNIEnv?>, _ clazz: jclass) -> jstring? {
// Exercise Swift Concurrency so the example links (and runs) the async
// runtime — see Greeter.greetingAsync().
Task {
_ = await Greeter(subject: "Android").greetingAsync()
}
let message = Greeter(subject: "Android").greeting()
return message.withCString { cString in
env.pointee!.pointee.NewStringUTF(env, cString)
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8 changes: 8 additions & 0 deletions swift/internal/extensions/swift_sdks.bzl
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Expand Up @@ -293,6 +293,14 @@ def _swift_android_sdk_impl(repository_ctx):
"-L{}/android".format(resource_dir),
"-llog",
"-lswiftCore",
# Swift Concurrency's global executor lives on libdispatch,
# but the dependency comes from C++ objects inside
# libswift_Concurrency.a, so it is never autolinked. Link it
# (and its BlocksRuntime) explicitly from the same SDK
# directory; lld only extracts referenced members, so this is
# free for binaries that don't use concurrency.
"-ldispatch",
"-lBlocksRuntime",
"-Wl,-export-dynamic",
"-Wl,--exclude-libs,ALL",
# TODO: Remove once https://github.com/bazelbuild/rules_android_ndk/commit/efc0c191796477c540e87e0f6bb5d88d6a58cc1f is in a release
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