Swift 6.2 Android SDK: zlib linking failure in libFoundationXML.so

[leogdion]

Description

Swift 6.2 Android SDK has a regression where libFoundationXML.so fails to find zlib symbols at runtime, causing any code using FoundationXML (XMLParser, XMLDocument, etc.) to crash.

Swift 6.1 works fine with the same code and configuration.

Environment

• Swift Version: 6.2 (release)
• Android API Level: 28 (also tested 33, 34)
• Architecture: x86_64 (ubuntu-latest runner)
• Action Version: skiptools/swift-android-action@v2
• Runner: GitHub Actions ubuntu-latest

Error

CANNOT LINK EXECUTABLE "./SyndiKitPackageTests.xctest":
cannot locate symbol "deflateInit2_" referenced by
"/data/local/tmp/android-xctest/libFoundationXML.so"

The symbol deflateInit2_ is part of zlib, which libxml2 depends on.

Reproduction

Test repository: brightdigit/SyndiKit

• Branch: test-android-swift-versions
• Uses XMLCoder package which depends on FoundationXML

Minimal workflow that reproduces:

```yaml

• uses: skiptools/swift-android-action@v2
  with:
  swift-version: "6.2"
  android-api-level: 28
  run-tests: true
  ```

Any Swift package using FoundationXML will fail.

Verification

Created test branch comparing Swift 6.1 vs 6.2:

• ✅ Swift 6.1: All tests pass
• ❌ Swift 6.2: Fails with zlib linking error

CI runs:

• Swift 6.1 passing
• Swift 6.2 failing

Expected Behavior

Swift 6.2 should include zlib (libz.so) in the Android SDK or ensure libFoundationXML.so is statically linked with zlib, matching the behavior of Swift 6.1.

Workaround

Temporarily using Swift 6.1 for Android builds until this is resolved.

Additional Context

• This appears to be a packaging/linking regression between 6.1 and 6.2
• The issue affects any use of FoundationXML on Android
• Architecture is x86_64 (not 32-bit ARM), so this is not related to the known NDK issue [BUG] libz.a for armeabi-v7a is missing symbols android/ndk#1391

---

Repository affected: brightdigit/SyndiKit
Test branch: test-android-swift-versions

[marcprux]

zlib is present as part of the NDK native APIs, so we shouldn't need to include it with the Swift SDK for Android. But we should be automatically linking it when linking to FoundationXML — I'm not sure how that regressed.

As a temporary workaround, you should be able to conditionally add it to the linked libraries in the Package.swift, like I do in Universal:

linkerSettings: [.linkedLibrary("z", .when(platforms: [.linux, .android]))]