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[SR-7634] EXC_BAD_ACCESS when using a Protocol which has a Constraint on it's definition #50175

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swift-ci opened this issue May 8, 2018 · 4 comments
Closed

[SR-7634] EXC_BAD_ACCESS when using a Protocol which has a Constraint on it's definition #50175

swift-ci opened this issue May 8, 2018 · 4 comments
Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself crash Bug: A crash, i.e., an abnormal termination of software run-time crash Bug → crash: Swift code crashed during execution

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@swift-ci
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swift-ci commented May 8, 2018

Previous ID SR-7634
Radar rdar://problem/40059422
Original Reporter georgemp (JIRA User)
Type Bug
Status Closed
Resolution Duplicate
Environment

OS X 10.13.4

XCode 9.3 (9E145)

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, CompilerCrash, RunTimeCrash
Assignee georgemp (JIRA)
Priority Medium

md5: c2650d576005727d191e3766798dc932

duplicates:

  • SR-6000 Let protocols inherit from class types

Issue Description:

I'm trying to constrain a protocol to instances of a certain class (or it's subclasses). The compiler doesn't complain about the following code (and, seems to restrict the protocol to the specified class)

import Foundation

class C {}

protocol P where Self: C {
    var x: Int { get }
    var y: Int { get }
}

extension P {
    var x: Int { return 42 }
}

class D: C, P {
    var y: Int { return x + 1 }
}

func f(vc: C) {
    if let vc = vc as? P {
        print(vc.x)
        print(vc.y)
    }
}

f(vc: D())

However, running the code causes a crash.

* thread #​1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
    frame #​0: 0x0000000000000000
    frame #​1: 0x0000000100001fee ProtocolConstraintBug`protocol witness for P.y.getter in conformance D at main.swift:0
  * frame #​2: 0x0000000100002363 ProtocolConstraintBug`f(vc=0x0000000103104230) at main.swift:29
    frame #​3: 0x0000000100001da6 ProtocolConstraintBug`main at main.swift:33
    frame #​4: 0x00007fff56379015 libdyld.dylib`start + 1
    frame #​5: 0x00007fff56379015 libdyld.dylib`start + 1

Moving the constraint to the protocol extension seems to work

import Foundation

class C {}

protocol P {
    var x: Int { get }
    var y: Int { get }
}

extension P where Self: C {
    var x: Int { return 42 }
}

class D: C, P {
    var y: Int { return x + 1 }
}

func f(vc: C) {
    if let vc = vc as? P {
        print(vc.x)
        print(vc.y)
    }
}

f(vc: D())
@belkadan
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belkadan commented May 8, 2018

With assertions enabled:

TYPE MISMATCH IN ARGUMENT 0 OF APPLY AT expression at [<stdin>:18:15 - line:18:18] RangeText="vc.x"
  argument value:   %36 = alloc_stack $@opened("D5ADD730-52D8-11E8-BCAF-9A0002AC2BC0") P // type-defs: %35; user: %37
  parameter type: $@opened("D5ADD730-52D8-11E8-BCAF-9A0002AC2BC0") P

1.  While emitting SIL for 'f(vc:)' at <stdin>:16:1
2.  While silgen emitFunction SIL function "@$S4main1f2vcyAA1CC_tF".

@slavapestov's been fixing a bunch of these but I guess he didn't get to this one.

@swift-ci create

@AnnaZaks
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AnnaZaks mannequin commented Jul 23, 2019

I cannot reproduce, getting:
42
43
Program ended with exit code: 0

So looks like this has been fixed.

georgemp (JIRA User), Could you verify if the problem is fixed and if so move the JIRA to "Closed"?

Thanks!
Anna

@swift-ci
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Comment by Malayil Philip George (JIRA)

Hi,

I tried the tests again

Xcode 10.1 - Crashes

Xcode 10.2.1 - No Crash

Xcode 10.3 - No Crash

Looks like it's been fixed. Thanks

@swift-ci
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Comment by Malayil Philip George (JIRA)

Doesn't crash on Xcode 10.2.1 and 10.3

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@AnthonyLatsis AnthonyLatsis added the crash Bug: A crash, i.e., an abnormal termination of software label Oct 22, 2022
This issue was closed.
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself crash Bug: A crash, i.e., an abnormal termination of software run-time crash Bug → crash: Swift code crashed during execution
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@belkadan @swift-ci @AnthonyLatsis