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[SR-5137] Corrupt Return Value from Method Returning Tuple #47713

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troughton opened this issue Jun 7, 2017 · 7 comments
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[SR-5137] Corrupt Return Value from Method Returning Tuple #47713

troughton opened this issue Jun 7, 2017 · 7 comments
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@aschwaighofer
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself regression swift 4.0

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@troughton
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Previous ID SR-5137
Radar rdar://problem/32618125
Original Reporter @troughton
Type Bug
Status Resolved
Resolution Done

Attachment: Download

Environment

Swift 4.0/Swift 3.2, Xcode 9 beta

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, 4.0Regression, Miscompile
Assignee @aschwaighofer
Priority Medium

md5: 1da37c68a65328553195e7c579800594

Issue Description:

In Swift 4/Swift 3.2 mode, return values of a function that returns a tuple are corrupted.

Within the method, variables have the correct value, but outside of it they have an incorrect value returned. I've attached an example project that exhibits this issue.

This code compiled correctly in Swift 3 (Xcode 8.3.2).

e.g.

extension Matrix4x4f {
    public var decomposed : (translation: Vector3f, rotation: Quaternion, scale: Vector3f) {
        let translation = ...
        let scale = ...
        let rotation = ...
        
        print("Value within method: \(translation), \(rotation), \(scale)")
        return (translation, rotation, scale)
    }
}

let matrix = Matrix4x4f.lookAt(eye: Vector3f(1, 1, 1), at: Vector3f(0, 0, 0))

let (translation, rotation, scale) = matrix.decomposed
print("Value returned: \(translation), \(rotation), \(scale)")

outputs:

Value within method: Vector3f(x: -0.0, y: -0.0, z: 1.73205), Quaternion(x: -0.115917, y: 0.880476, z: -0.279848, w: 0.364705), Vector3f(x: 1.0, y: 1.0, z: 1.0)
Value returned: Vector3f(x: -0.0, y: -0.0, z: 1.73205), Quaternion(x: 0.0, y: 0.0, z: -0.279848, w: 0.364705), Vector3f(x: 1.0, y: 1.0, z: 0.0)
@belkadan
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belkadan commented Jun 7, 2017

@swift-ci create

@troughton
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I may have accidentally uploaded a non-working project before; apologies if you tried to run it. I've fixed the issues in the project in swift4bug.zip and you should now be able to run it without problems.

@bob-wilson
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I was just about to ask about that. The revised project builds with Xcode 8.3.2 but the output just shows "Opaque Value":

Value within method: Vector3f(d: simd.float3(_vector: (Opaque Value))), Quaternion(x: Swift.Float(_value: (Opaque Value)), y: Swift.Float(_value: (Opaque Value)), z: Swift.Float(_value: (Opaque Value)), w: Swift.Float(_value: (Opaque Value))), Vector3f(d: simd.float3(_vector: (Opaque Value)))
Value returned: Vector3f(d: simd.float3(_vector: (Opaque Value))), Quaternion(x: Swift.Float(_value: (Opaque Value)), y: Swift.Float(_value: (Opaque Value)), z: Swift.Float(_value: (Opaque Value)), w: Swift.Float(_value: (Opaque Value))), Vector3f(d: simd.float3(_vector: (Opaque Value)))

@troughton
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That's doubly odd. I downloaded the project again and I'm getting the same results – but Vector3.swift declares a conformance to CustomStringConvertible, and so my understanding is that that should be called when 'print'ing the value – maybe that's a second bug? Calling .description on the objects seems to work – I'll upload another project that does that soon.

That output was also from running that original test case code, so perhaps Xcode was using an old module cache or something like that, and as such I was getting the correct output? I'm not entirely sure – just worth pointing out that I did get the output above by running the first project I submitted.

@troughton
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See 'Swift 4 Bug - Amended.zip' for a version that I've just tested across two different computers after running a clean build and that displays the issue on Xcode 9 beta for me. If that also has issues then I'll be very perplexed.

@bob-wilson
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OK, I can reproduce it with that latest version.

@aschwaighofer
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Fixed: #10501

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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@aschwaighofer aschwaighofer

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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself regression swift 4.0
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@belkadan @troughton @aschwaighofer @bob-wilson @AnthonyLatsis