Workaround test crashing when compiled in release mode on Swift 6.2 by simonjbeaumont · Pull Request #3511 · apple/swift-nio

simonjbeaumont · 2026-02-18T14:21:34Z

Motivation:

Our post-merge, pre-release pipelines run tests for our supported Swift versions in both debug and release mode. The recent PR to add withUnsafeTransportIfAvailable added some tests for various valid and invalid usages of the API. One of the invalid usages was causing the tests to crash, when compiled in release mode, in the Swift runtime:

% docker run --rm -it -v $PWD:/pwd -w /pwd swift:6.2 swift test --filter testUnderlyingSocketAccessForSocketBasedChannel
[1/1] Planning build
Building for debugging...
[1/1] Write swift-version-24593BA9C3E375BF.txt
Build complete! (2.38s)
Test Suite 'Selected tests' started at 2026-02-18 13:28:18.905
Test Suite 'Selected tests' passed at 2026-02-18 13:28:18.905
         Executed 0 tests, with 0 failures (0 unexpected) in 0.0 (0.0) seconds
◇ Test run started.
↳ Testing Library Version: 6.2.3 (48a471ab313e858)
↳ Target Platform: aarch64-unknown-linux-gnu
◇ Suite NIOTransportAccessibleChannelCoreTests started.
◇ Test testUnderlyingSocketAccessForSocketBasedChannel() started.
✔ Test testUnderlyingSocketAccessForSocketBasedChannel() passed after 0.005 seconds.
✔ Suite NIOTransportAccessibleChannelCoreTests passed after 0.005 seconds.
✔ Test run with 1 test in 1 suite passed after 0.005 seconds.

% docker run --rm -it -v $PWD:/pwd -w /pwd swift:6.2 swift test -c release --filter testUnderlyingSocketAccessForSocketBasedChannel
[1/1] Planning build
Building for production...
[1/1] Write swift-version-24593BA9C3E375BF.txt
Build complete! (2.12s)
Test Suite 'Selected tests' started at 2026-02-18 13:27:12.102
Test Suite 'Selected tests' passed at 2026-02-18 13:27:12.103
         Executed 0 tests, with 0 failures (0 unexpected) in 0.0 (0.0) seconds
◇ Test run started.
↳ Testing Library Version: 6.2.3 (48a471ab313e858)
↳ Target Platform: aarch64-unknown-linux-gnu
◇ Suite NIOTransportAccessibleChannelCoreTests started.
◇ Test testUnderlyingSocketAccessForSocketBasedChannel() started.

*** Signal 11: Backtracing from 0xffff8854b1ec... done ***

*** Program crashed: Bad pointer dereference at 0x0000000000000000 ***

Platform: arm64 Linux (Ubuntu 24.04.4 LTS)

Thread 0 "NIO-ELT-1-#1" crashed:

  0                0x0000ffff8854b1ec tryCast(swift::OpaqueValue*, swift::TargetMetadata<swift::InProcess> const*, swift::OpaqueValue*, swift::TargetMetadata<swift::InProcess> const*, swift::TargetMetadata<swift::InProcess> const*&, swift::TargetMetadata<swift::InProcess> const*&, bool, bool, bool) + 52 in libswiftCore.so
  1 [ra]           0x0000ffff8854b148 swift_dynamicCast + 79 in libswiftCore.so
  2 [ra] [system]  0x0000aaaab8668588 specialized ChannelPipeline.SynchronousOperations.withUnsafeTransportIfAvailable<A, B>(of:_:) + 135 in swift-nioPackageTests.xctest at //<compiler-generated>
  3 [ra]           0x0000aaaab8668148 closure #1 in NIOTransportAccessibleChannelCoreTests.testUnderlyingSocketAccessForSocketBasedChannel() + 3103 in swift-nioPackageTests.xctest at /tmp/swift-generated-sources/@__swiftmacro_13NIOPosixTests0049NIOTransportAccessibleChannelCoreTestsswift_IhHJqfMX55_16_33_309B77F97E02F918EDFF07092681CD49Ll6expectfMf8_.swift:1:40
  4 [ra] [thunk]   0x0000aaaab866be1c partial apply for closure #1 in NIOTransportAccessibleChannelCoreTests.testUnderlyingSocketAccessForSocketBasedChannel() + 15 in swift-nioPackageTests.xctest at //<compiler-generated>
  5 [ra]           0x0000aaaab7f410ec closure #1 in EventLoop.submit<A>(_:) + 95 in swift-nioPackageTests.xctest at /pwd/Sources/NIOCore/EventLoop.swift:1030:69
  6 [ra] [inlined] 0x0000aaaab841d468 closure #1 in SelectableEventLoop.run(_:) in swift-nioPackageTests.xctest at /pwd/Sources/NIOPosix/SelectableEventLoop.swift:618:17
  7 [ra] [inlined] 0x0000aaaab841d468 specialized withAutoReleasePool<A>(_:) in swift-nioPackageTests.xctest at /pwd/Sources/NIOPosix/SelectableEventLoop.swift:49:16
  8 [ra] [inlined] 0x0000aaaab841d468 SelectableEventLoop.run(_:) in swift-nioPackageTests.xctest at /pwd/Sources/NIOPosix/SelectableEventLoop.swift:615:9
  9 [ra]           0x0000aaaab841d468 SelectableEventLoop.runOneLoopTick(selfIdentifier:) + 535 in swift-nioPackageTests.xctest at /pwd/Sources/NIOPosix/SelectableEventLoop.swift:809:22
 10 [ra]           0x0000aaaab8423e5c SelectableEventLoop.run() + 331 in swift-nioPackageTests.xctest at /pwd/Sources/NIOPosix/SelectableEventLoop.swift:923:38
 11 [ra] [inlined] 0x0000aaaab83de614 static MultiThreadedEventLoopGroup.runTheLoop(thread:uniqueID:parentGroup:canEventLoopBeShutdownIndividually:selectorFactory:initializer:metricsDelegate:_:) in swift-nioPackageTests.xctest at /pwd/Sources/NIOPosix/MultiThreadedEventLoopGroup.swift:117:22
 12 [ra]           0x0000aaaab83de614 closure #1 in static MultiThreadedEventLoopGroup.setupThreadAndEventLoop(name:uniqueID:parentGroup:selectorFactory:initializer:metricsDelegate:) + 1255 in swift-nioPackageTests.xctest at /pwd/Sources/NIOPosix/MultiThreadedEventLoopGroup.swift:139:41
 13 [ra] [thunk]   0x0000aaaab83e1eec partial apply for closure #1 in static MultiThreadedEventLoopGroup.setupThreadAndEventLoop(name:uniqueID:parentGroup:selectorFactory:initializer:metricsDelegate:) + 39 in swift-nioPackageTests.xctest at //<compiler-generated>
 14 [ra] [thunk]   0x0000aaaab843f534 thunk for @escaping @callee_guaranteed (@guaranteed NIOThread) -> () + 23 in swift-nioPackageTests.xctest at //<compiler-generated>
 15 [ra]           0x0000aaaab84409dc closure #1 in closure #1 in static ThreadOpsPosix.run(handle:args:) + 319 in swift-nioPackageTests.xctest at /pwd/Sources/NIOPosix/ThreadPosix.swift:186:21
 16 [ra]           0x0000ffff86af595c <unknown> in libc.so.6
...


Registers:

 x0 0x0000ffff62fddfe0  48 60 00 58 ff ff 00 00 e0 e0 fd 62 ff ff 00 00  H`·Xÿÿ··ààýbÿÿ··
 x1 0x0000000000000000  0
 x2 0x0000ffff62fddff0  40 b4 01 5c ff ff 00 00 20 83 d1 b8 aa aa 00 00  @´·\ÿÿ·· ·Ñ¸ªª··
 x3 0x0000ffff58002038  03 03 00 00 00 00 00 00 01 00 00 00 01 00 00 00  ················
 x4 0x0000ffff62fddfa8  00 00 00 00 00 00 00 00 00 e0 fd 62 ff ff 00 00  ·········àýbÿÿ··
 x5 0x0000ffff62fddfa0  38 20 00 58 ff ff 00 00 00 00 00 00 00 00 00 00  8 ·Xÿÿ··········
 x6 0x0000000000000001  1
 x7 0x0000000000000000  0
 x8 0x0000000000000000  0
 x9 0x0000ffff886cf4e8  98 73 54 88 ff ff 00 00 08 be 5b 88 ff ff 00 00  ·sT·ÿÿ···¾[·ÿÿ··
x10 0x000000000000ffff  65535
x11 0x0000000000000000  0
x12 0x0000000000000000  0
x13 0x0000000000000001  1
x14 0x0000aaaab8e3ff2c  05 00 00 00 d4 2e a7 ff 00 00 03 00 51 00 00 00  ····Ô.§ÿ····Q···
x15 0x0000000000000009  9
x16 0x0000aaaab8d70520  f8 b0 54 88 ff ff 00 00 b4 45 55 88 ff ff 00 00  ø°T·ÿÿ··´EU·ÿÿ··
x17 0x0000ffff8854b0f8  ff 43 01 d1 fd 7b 02 a9 f6 57 03 a9 f4 4f 04 a9  ÿC·Ñý{·©öW·©ôO·©
x18 0x0000000000000000  0
x19 0x0000ffff58002038  03 03 00 00 00 00 00 00 01 00 00 00 01 00 00 00  ················
x20 0x0000ffff62fddff0  40 b4 01 5c ff ff 00 00 20 83 d1 b8 aa aa 00 00  @´·\ÿÿ·· ·Ñ¸ªª··
x21 0x0000000000000006  6
x22 0x0000000000000000  0
x23 0x0000aaaab86688b0  09 00 40 f9 09 01 00 f9 c0 03 5f d6 ff c3 00 d1  ··@ù···ùÀ·_ÖÿÃ·Ñ
x24 0x0000ffff5c01b440  f0 9d d9 b8 aa aa 00 00 03 00 00 00 08 00 00 00  ð·Ù¸ªª··········
x25 0x0000aaaab8d18320  0c 9c e2 b8 aa aa 00 00 ec 3c 3a b8 aa aa 00 00  ··â¸ªª··ì<:¸ªª··
x26 0x0000ffff62fde170  6e 69 6c 00 00 00 00 00 00 00 00 00 00 00 00 e3  nil············ã
x27 0x0000ffff62fde0e0  2d 00 00 00 00 00 00 d0 a0 3b de b8 aa aa 00 80  -······Ð ;Þ¸ªª··
x28 0x0000ffff886c6c28  02 02 00 00 00 00 00 00 30 b0 6f 88 ff ff 00 00  ········0°o·ÿÿ··
 fp 0x0000ffff62fddf30  b0 df fd 62 ff ff 00 00 48 b1 54 88 ff ff 00 00  °ßýbÿÿ··H±T·ÿÿ··
 lr 0x0000ffff8854b148  1f 08 00 71 c0 00 00 54 1f 04 00 71 c1 00 00 54  ···qÀ··T···qÁ··T
 sp 0x0000ffff62fddf00  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ················
 pc 0x0000ffff8854b1ec  68 01 40 f9 69 00 40 f9 1f fd 1f f1 f3 83 88 1a  h·@ùi·@ù·ý·ñó···


Images (20 omitted):

0x0000aaaab7d20000–0x0000aaaab8cd6d00 a17d4d145f2d2621f7b9d43c2b2d2a754b69002b swift-nioPackageTests.xctest /pwd/.build/aarch64-unknown-linux-gnu/release/swift-nioPackageTests.xctest
0x0000ffff86a70000–0x0000ffff86c09ec1 d5ef86dde36cbd3289566cf5098226035d76f2e1 libc.so.6                    /usr/lib/aarch64-linux-gnu/libc.so.6
0x0000ffff88160000–0x0000ffff8869e0c8 f62b9374639c58d0b60814a6fbec69d2b596cfc7 libswiftCore.so              /usr/lib/swift/linux/libswiftCore.so

Backtrace took 0.62s

error: Exited with unexpected signal code 11

The test is fine for both debug and release mode on Swift 6.0, 6.1, and 6.3-nightly.

Modifications:

Since this is a valid construction and the crash is a Swift bug, and since it only manifests on a specific Swift version, and since it's only triggered when mis-using the API, we can just not perform this part of the test on Swift 6.2. The API is fully functional when used correctly.

Result:

Running NIO tests, compiled in release mode, no longer crashes on Swift 6.2.3.

Local testings:

With this branch:

% docker run --rm -it -v $PWD:/pwd -w /pwd swift:6.2 swift test -c release --filter testUnderlyingSocketAccessForSocketBasedChannel
[1/1] Planning build
Building for production...
[8/8] Linking swift-nioPackageTests.xctest
Build complete! (38.46s)
Test Suite 'Selected tests' started at 2026-02-18 14:23:12.902
Test Suite 'Selected tests' passed at 2026-02-18 14:23:12.902
         Executed 0 tests, with 0 failures (0 unexpected) in 0.0 (0.0) seconds
◇ Test run started.
↳ Testing Library Version: 6.2.3 (48a471ab313e858)
↳ Target Platform: aarch64-unknown-linux-gnu
◇ Suite NIOTransportAccessibleChannelCoreTests started.
◇ Test testUnderlyingSocketAccessForSocketBasedChannel() started.
✔ Test testUnderlyingSocketAccessForSocketBasedChannel() passed after 0.002 seconds.
✔ Suite NIOTransportAccessibleChannelCoreTests passed after 0.003 seconds.
✔ Test run with 1 test in 1 suite passed after 0.003 seconds.

Workaround test crashing when compiled in release mode on Swift 6.2

06cf3ec

simonjbeaumont added the 🔨 semver/patch No public API change. label Feb 18, 2026

simonjbeaumont marked this pull request as ready for review February 18, 2026 14:23

simonjbeaumont added semver/none No version bump required. and removed 🔨 semver/patch No public API change. labels Feb 18, 2026

simonjbeaumont enabled auto-merge (squash) February 18, 2026 14:34

rnro approved these changes Feb 18, 2026

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simonjbeaumont merged commit e932d3c into apple:main Feb 18, 2026
57 of 58 checks passed

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Workaround test crashing when compiled in release mode on Swift 6.2#3511

Workaround test crashing when compiled in release mode on Swift 6.2#3511
simonjbeaumont merged 1 commit intoapple:mainfrom
simonjbeaumont:sb/workaround-6.2-release-test-crasher

simonjbeaumont commented Feb 18, 2026 •

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simonjbeaumont commented Feb 18, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Motivation:

Modifications:

Result:

Local testings:

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simonjbeaumont commented Feb 18, 2026 •

edited

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