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[SR-5153] Miscompile in Swift 3.2 results in zombie message (regression from 3.1) #4089

swift-ci opened this issue Jun 7, 2017 · 4 comments


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swift-ci commented Jun 7, 2017

Previous ID SR-5153
Radar rdar://problem/32625475
Original Reporter benasher44 (JIRA User)
Type Bug
Status Closed
Resolution Cannot Reproduce

macOS Sierra 10.12.5
Xcode 9 beta 1
Swift 3.2/4

Additional Detail from JIRA
Votes 0
Component/s Compiler, Foundation
Labels Bug, 4.0Regression, RunTimeCrash
Assignee None
Priority Medium

md5: 662f5f52aa64a4841c2845dda9fc7d09

Issue Description:

Consider the following code, which runs error-free in Swift 3.1, but results in a runtime crash in Swift 3.2 and Swift 4:

import Foundation

struct S {
  var str = UUID().uuidString

func go() {
    var s = S()
    s = S()

    _ = .default).async {


This crashes using swift that ships with Xcode 9 beta 1 by running it in the following ways:
swift -swift-version 3 file.swift
swift file.swift

Output from the program:

0 swift 0x00000001110823aa PrintStackTraceSignalHandler(void*) + 42
1 swift 0x00000001110817e6 SignalHandler(int) + 662
2 libsystem_platform.dylib 0x00007fffb6d64b3a _sigtramp + 26
3 libsystem_platform.dylib 000000000000000000 _sigtramp + 1227470048
4 libsystem_platform.dylib 0x0000000113ad1744 _sigtramp + 1557580836
5 libswiftCore.dylib 0x00000001167a6770 _swift_release_dealloc + 16
6 libswiftCore.dylib 0x0000000113ad1894 _swift_release_dealloc + 4247957812
7 libsystem_blocks.dylib 0x00007fffb6b89952 _Block_release + 102
8 libdispatch.dylib 0x00007fffb6b1f8fc _dispatch_client_callout + 8
9 libdispatch.dylib 0x00007fffb6b2e196 _dispatch_queue_override_invoke + 743
10 libdispatch.dylib 0x00007fffb6b216b5 _dispatch_root_queue_drain + 476
11 libdispatch.dylib 0x00007fffb6b2148c _dispatch_worker_thread3 + 99
12 libsystem_pthread.dylib 0x00007fffb6d6e5a2 _pthread_wqthread + 1299
13 libsystem_pthread.dylib 0x00007fffb6d6e07d start_wqthread + 13
Killed: 9

In Instruments, you can see that the string held by s is released an extra time.

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Contributor Author

swift-ci commented Jun 7, 2017

Comment by Ben A (JIRA)

Ben-G (JIRA User) spoke with @jckarter about this one at the lab today.

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belkadan commented Jun 7, 2017

@swift-ci create

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Contributor Author

swift-ci commented Aug 2, 2017

Comment by Matt Rajca (JIRA)

Looks fixed in (swiftlang-900.0.58 clang-900.0.33).

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Yep, this was
master: apple/swift#10278
4.0: apple/swift#10283

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@shahmishal shahmishal transferred this issue from apple/swift May 5, 2022
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