swift test --filter with --sanitize fails: "Sanitizer load violates platform policy"

[naftaly]

Is it reproducible with SwiftPM command-line tools: swift build, swift test, swift package etc?

• Confirmed reproduction steps with SwiftPM CLI. The description text must include reproduction steps with either of command-line SwiftPM commands, swift build, swift test, swift package etc.

Description

When running swift test with both --filter and --sanitize flags, the test fails to execute because the sanitizer runtime library cannot be loaded into the xctest subprocess.

Environment:

• Swift: 6.2.3 (swiftlang-6.2.3.3.21)
• Xcode: 26.2
• macOS: 26.1 (Build 25B78)
• Architecture: arm64

Steps to Reproduce:

1. Create or use any Swift package with tests
2. Run: swift test --sanitize address --filter

Expected behavior

Tests matching the filter run with AddressSanitizer enabled.

Actual behavior

Build succeeds, but test execution fails with:

Library not loaded: '@rpath/libclang_rt.asan_osx_dynamic.dylib'
...
code signature in '/Applications/Xcode-26.2.0.app/.../libclang_rt.asan_osx_dynamic.dylib'
not valid for use in process: Sanitizer load violates platform policy

Workaround:

Running without --filter works correctly:
swift test --sanitize address # ✓ works
swift test --sanitize address --filter Foo # ✗ fails

Analysis:

When --filter is used, Swift PM spawns xctest as a subprocess to run filtered tests. The sanitizer runtime's code signature appears to be rejected by macOS platform policy when loaded into this subprocess, but works when tests run directly without the filter mechanism.

Steps to reproduce

No response

Swift Package Manager version/commit hash

No response

Swift & OS version (output of swift --version ; uname -a)

swift-driver version: 1.127.14.1 Apple Swift version 6.2.3 (swiftlang-6.2.3.3.21 clang-1700.6.3.2)
Target: arm64-apple-macosx26.0
Darwin Alex-M3-Air.local 25.1.0 Darwin Kernel Version 25.1.0: Mon Oct 20 19:26:04 PDT 2025; root:xnu-12377.41.6~2/RELEASE_ARM64_T8122 arm64

[Viditgupta-official]

I can reproduce this locally on macOS arm64 using the SwiftPM CLI.
Running swift test --sanitize address --filter fails with
Sanitizer load violates platform policy, while --sanitize or --filter alone works as expected.

I’m planning to add SwiftPM coverage for the swift test --sanitize --filter combination to isolate the failure and better understand where the planning/execution diverges. Happy to take a look at a fix once there’s a failing test.

[stmontgomery]

This is a bug in the swiftpm-xctest-helper executable tool, which is an Xcode tool not part of this repository. The problem will need to be tracked separately, via an Apple Feedback.

[Viditgupta-official]

That makes sense — since the failure comes from swiftpm-xctest-helper (Xcode tool), I’ve kept the PR focused purely on adding coverage/documentation for the swift test --sanitize --filter behavior.

The test is now marked as a known issue / expected failure on macOS, so it doesn’t block CI while still making the behavior explicit and easier to track until the underlying Xcode issue is resolved.