Allow building on Linux

[lhoward]

Linux build fixes, pending whilst resolving test failures.

[lhoward]

Swift version:

lukeh@liebling:~/CVSRoot/padl/AsyncExtensions-1$ swift --version
Swift version 5.9-dev (LLVM edfa23b742ff932, Swift 18d8d9b752723b6)
Target: aarch64-unknown-linux-gnu

Test failures:

Test Case 'AsyncCurrentValueSubjectTests.test_subject_handles_concurrency' started at 2023-07-19 05:19:15.360
Process 90935 stopped
* thread #2, name = 'AsyncExtensions', stop reason = signal SIGTRAP
    frame #0: 0x0000fffff6dfa0f0 libXCTest.so`XCTest.XCTestCase.waitForExpectations(timeout: Swift.Double, file: Swift.StaticString, line: Swift.Int, handler: Swift.Optional<(Swift.Optional<Swift.Error>) -> ()>) -> () + 820
libXCTest.so`XCTest.XCTestCase.waitForExpectations(timeout: Swift.Double, file: Swift.StaticString, line: Swift.Int, handler: Swift.Optional<(Swift.Optional<Swift.Error>) -> ()>) -> ():
->  0xfffff6dfa0f0 <+820>: brk    #0x1

libXCTest.so`lazy protocol witness table accessor for type XCTest.XCTWaiter.Result and conformance XCTest.XCTWaiter.Result : Swift.RawRepresentable in XCTest:
    0xfffff6dfa0f4 <+0>:   stp    x29, x30, [sp, #-0x10]!
    0xfffff6dfa0f8 <+4>:   adrp   x8, 45
    0xfffff6dfa0fc <+8>:   mov    x29, sp
Target 0: (AsyncExtensionsPackageTests.xctest) stopped.
(lldb) bt
* thread #2, name = 'AsyncExtensions', stop reason = signal SIGTRAP
  * frame #0: 0x0000fffff6dfa0f0 libXCTest.so`XCTest.XCTestCase.waitForExpectations(timeout: Swift.Double, file: Swift.StaticString, line: Swift.Int, handler: Swift.Optional<(Swift.Optional<Swift.Error>) -> ()>) -> () + 820
    frame #1: 0x0000aaaaaac005d8 AsyncExtensionsPackageTests.xctest`AsyncCurrentValueSubjectTests.test_subject_handles_concurrency(self=0x0000aaaaab2b7820) at AsyncCurrentValueSubjectTests.swift:178:11
    frame #2: 0x0000fffff78f5578 libswift_Concurrency.so`swift::runJobInEstablishedExecutorContext(swift::Job*) + 408
    frame #3: 0x0000fffff78f5e98 libswift_Concurrency.so`swift_job_run + 96
    frame #4: 0x0000fffff772a818 libdispatch.so`_dispatch_continuation_pop + 236
    frame #5: 0x0000fffff772a614 libdispatch.so`_dispatch_async_redirect_invoke + 216
    frame #6: 0x0000fffff7735948 libdispatch.so`_dispatch_worker_thread + 440
    frame #7: 0x0000fffff696d5c8 libc.so.6`start_thread(arg=0x0000000000000000) at pthread_create.c:442:8
    frame #8: 0x0000fffff69d5d1c libc.so.6`thread_start at clone.S:79
(lldb) up

[lhoward]

On my list to fix!

[lhoward]

I get a bit further:

• using latest build from main rather than 5.9 snapshot
• applying #36
• further patches to ensure await fulfillment(of:timeout:) is used rather than wait(for:timeout:)

However now it fails here:

Test Suite 'AsyncWithLatestFrom2SequenceTests' started at 2023-07-31 02:19:32.686
Test Case 'AsyncWithLatestFrom2SequenceTests.test_withLatestFrom_finishes_loop_when_task_is_cancelled' started at 2023-07-31 02:19:32.686
/home/lukeh/CVSRoot/padl/AsyncExtensions-1/Tests/Combiners/WithLatestFrom/AsyncWithLatestFrom2SequenceTests.swift:212: error: AsyncWithLatestFrom2SequenceTests.test_withLatestFrom_finishes_loop_when_task_is_cancelled : Asynchronous wait failed - Exceeded timeout of 5.0 seconds, with unfulfilled expectations: The iteration has produced 1 element

If I don't apply the patches, then it fails unwrapping firstElement in AsyncWithLatestFrom2SequenceTests.swift:

    let task = Task(priority: .high) {
      var iterator = sequence.makeAsyncIterator()

      var firstIteration = false
      var firstElement: (Int, String, String)?
      while let element = await iterator.next() {
        if !firstIteration {
          firstElement = element
          firstIteration = true
          iterated.fulfill()
        }
      }
      XCTAssertEqual(Tuple3(firstElement!), Tuple3((1, "a", "x")))

      finished.fulfill()
    }

[woko666]

@lhoward Great work on linux support, I've tried your latest commits and it's working quite well for me. Are there still any issues you know of? If so, would you appreciate some assistance?

[lhoward]

I’m still using the branch, haven’t made any progress with test that fails unfortunately but it’s working fine in my application.

[0xfeedface1993]

During my latest tests, I discovered that the closures inside Task and TaskGroup were not executed when created, which resulted in downstream operations like zip not receiving any events from upstream. This issue only occurs on Linux. I suspect there might be a bug in Swift's Concurrency framework, and I am still looking for a workaround.