Use the new `#available(Android <API>, *)` instead to look for `backtrace()` by finagolfin · Pull Request #1546 · swiftlang/swift-testing

finagolfin · 2026-02-12T09:54:46Z

Mads added this compiler feature for Android in swiftlang/swift#84574 before the 6.3 branch, so update the Android triples and NDK version to test it, as it requires NDK 28 or later.

@grynspan, just a pure rebased copy of #1373, unfortunately, may be a while before we can merge it.

grynspan · 2026-02-12T14:19:11Z

Converted to a draft since it's not possible to safely merge it yet.

finagolfin · 2026-02-20T04:09:14Z

Rebased and changed official workflow version to get an NDK fix, swiftlang/github-workflows#235, so this pull's CI finally uses the NDK 28 it requires and passes.

This change requires Android NDK 28 or later, but the Swift SDK for Android is still stuck on LTS NDK 27, which doesn't have the header annotations to support this Android availability feature.

I just tried changing the availability condition to if __NDK_MAJOR__ > 27, #available(Android 33, *) {, using that NDK C define, which worked fine with NDK 29 but doesn't compile with NDK 27, as it still looks for backtrace without the required NDK header changes, /home/finagolfin/swift-testing/Sources/Testing/SourceAttribution/Backtrace.swift:82:27: error: cannot find 'backtrace' in scope.

I think this would be fixed if we had compile-time NDK versioning, swiftlang/swift#81402, but for now, users will have to choose one NDK or the other and we cannot merge this till all Android CI switch to NDK 28 or later.

grynspan · 2026-02-20T15:35:31Z

I just tried changing the availability condition to if __NDK_MAJOR__ > 27, #available(Android 33, *) {, using that NDK C define, which worked fine with NDK 29 but doesn't compile with NDK 27, as it still looks for backtrace without the required NDK header changes, /home/finagolfin/swift-testing/Sources/Testing/SourceAttribution/Backtrace.swift:82:27: error: cannot find 'backtrace' in scope.

Yeah that's not surprising; the __NDK_MAJOR__ test is a runtime test (optimized away obviously) and the symbol is still "needed" at least in debug builds.

I probably said "don't do this" previously, but to cut the knot: maybe add an swt_backtrace() thunk in Stubs.h that checks #if __NDK_MAJOR >= 33 and skip the runtime checks for now?

finagolfin · 2026-02-20T15:46:14Z

Heh, nice idea but I'd rather not resort to C, will just wait till we update the NDK. 👍

finagolfin · 2026-04-12T00:45:06Z

Rebased and updated the workflow version to build this against the 6.3 release, no problem, with the trunk snapshot failures a known issue for all SDKs- hence the trunk wasm failures too- that we're told will be fixed in the next trunk tag.

The plan is to update the trunk Android CI to a newer NDK soon, after which the only question is whether we should try to get this into 6.3 too, which will require updating the 6.3 CI to NDK 28+ also.

finagolfin · 2026-04-21T03:05:45Z

Alright, this is finally ready to go, now that both trunk CI that build Android SDKs have been switched to NDK 28c, the minimum NDK version that supports this availability feature, and I made sure this CI only ~~tests~~builds this Android code with the trunk snapshot Android bundles and those newer NDKs.

Pinging @swiftlang/android-workgroup and the Testing reviewers for any final review.

grynspan · 2026-04-21T15:36:23Z

      enable_freebsd_checks: true
      freebsd_swift_versions: '["nightly-main"]'
      freebsd_os_versions: '["14.3"]'
+      android_sdk_versions: '["nightly-main"]'


Are similar changes required in the other workflow files?

I'll take a look.

I see no other workflows in this repo building for Android, is there somewhere else you think we should enable Android also?

main_using_main and main_using_release should probably be building for Android, but if they're not currently then we can add that in a separate PR.

I added those and removed this android_sdk_versions restriction, as I believe building with 6.3 will work, provided we only use NDK 28 or above. We just don't want this pull merged back to the release/6.3 branch, which still supports NDK 27.

Passed all Android CI, as expected. 👍

…race()` Mads added this compiler feature for Android in swiftlang/swift#84574 before the 6.3 branch, so update the Android triples and NDK versions to test it, as it requires NDK 28 or later.

finagolfin · 2026-04-21T18:11:33Z

      enable_wasm_sdk_build: true
      wasm_sdk_versions: '["nightly-6.3"]'
+      enable_android_sdk_build: true
+      android_sdk_versions: '["6.3", "nightly-6.3"]'


Would you like me to update all the others to "6.3" also, as the 6.3 snapshots won't be tagged much going forward?

We can do that in a separate PR.

hjyamauchi · 2026-04-22T22:31:09Z

It seems that the BCNY CI started to fail during the Android xctest build after this change. What'd be the best way to fix it?

D:\r\_work\swift-build\swift-build\SourceCache\swift-testing\Sources\Testing\SourceAttribution\Backtrace.swift:71:27: error: cannot find 'backtrace' in scope
 69 |       if #available(Android 33, *) {
 70 |         initializedCount = addresses.withMemoryRebound(to: UnsafeMutableRawPointer.self) { addresses in
 71 |           .init(clamping: backtrace(addresses.baseAddress!, .init(clamping: addresses.count)))
    |                           `- error: cannot find 'backtrace' in scope
 72 |         }
 73 |       }
D:\r\_work\swift-build\swift-build\SourceCache\swift-testing\Sources\Testing\SourceAttribution\Backtrace.swift:71:62: error: cannot infer contextual base in reference to member 'init'
 69 |       if #available(Android 33, *) {
 70 |         initializedCount = addresses.withMemoryRebound(to: UnsafeMutableRawPointer.self) { addresses in
 71 |           .init(clamping: backtrace(addresses.baseAddress!, .init(clamping: addresses.count)))
    |                                                              `- error: cannot infer contextual base in reference to member 'init'
 72 |         }
 73 |       }

https://github.com/thebrowsercompany/swift-build/actions/runs/24752103243/job/72427215969

grynspan · 2026-04-22T23:06:46Z

What toolchain version are you using, and what NDK version?

hjyamauchi · 2026-04-23T01:19:53Z

We were using NDK r27 and updating to the NDK r28 seems to resolve the issue. Thank you

finagolfin requested review from briancroom, grynspan, harlanhaskins, jerryjrchen and stmontgomery as code owners February 12, 2026 09:54

finagolfin added android 🤖 Android support cross-compilation Compiling tests for other platforms than the host tech-debt 💾 reduces technical debt labels Feb 12, 2026

finagolfin mentioned this pull request Feb 12, 2026

Use the new #available(Android API, *) instead to look for backtrace() #1373

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grynspan added this to the Swift 6.4.0 (main) milestone Feb 12, 2026

grynspan assigned finagolfin Feb 12, 2026

grynspan marked this pull request as draft February 12, 2026 14:19

finagolfin force-pushed the droid branch 2 times, most recently from bd60401 to f43b73d Compare February 20, 2026 03:19

finagolfin force-pushed the droid branch from f43b73d to 9b4ce3f Compare March 17, 2026 10:51

finagolfin force-pushed the droid branch from 9b4ce3f to a43aaeb Compare April 12, 2026 00:19

finagolfin force-pushed the droid branch from 6a563e8 to c48ffa1 Compare April 21, 2026 02:32

finagolfin marked this pull request as ready for review April 21, 2026 02:57

grynspan reviewed Apr 21, 2026

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grynspan requested changes Apr 21, 2026

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finagolfin force-pushed the droid branch 2 times, most recently from 26f0e0d to 05e9581 Compare April 21, 2026 17:35

finagolfin changed the title ~~Use the new #available(Android <API>, *) instead from Swift 6.3 to look for backtrace()~~ Use the new #available(Android <API>, *) instead to look for backtrace() Apr 21, 2026

grynspan approved these changes Apr 21, 2026

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Use the new #available(Android <API>, *) instead to look for `backt…

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…race()` Mads added this compiler feature for Android in swiftlang/swift#84574 before the 6.3 branch, so update the Android triples and NDK versions to test it, as it requires NDK 28 or later.

finagolfin force-pushed the droid branch from 05e9581 to 29c2d5e Compare April 21, 2026 18:04

finagolfin commented Apr 21, 2026

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stmontgomery approved these changes Apr 21, 2026

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finagolfin merged commit ea09eda into swiftlang:main Apr 21, 2026
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finagolfin deleted the droid branch April 21, 2026 19:42

hjyamauchi mentioned this pull request Apr 23, 2026

Update Android NDK to r28c to fix build failure compnerd/swift-build#1105

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finagolfin commented Apr 21, 2026 •

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