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[SR-11643] Xcode 11.2 beta 2 Regression: runtime crash with generic Foundation Encoder #54053

groue opened this issue Oct 20, 2019 · 3 comments


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@groue groue commented Oct 20, 2019

Previous ID SR-11643
Radar rdar://problem/56443094
Original Reporter @groue
Type Bug

Attachment: Download


Xcode Version 11.2 beta 2 (11B44)

MacOS 10.14.6 (18G87)

Additional Detail from JIRA
Votes 2
Component/s Compiler
Labels Bug, 5.1Regression, RunTimeCrash
Assignee None
Priority Medium

md5: b518bac98f64f18f48b7a0e0d3852343

Issue Description:


When an Encoder is generic and defined in a Swift Package library module, an Xcode app can't import this module and use this encoder without crashing right between the instantiation of the encoder and the call to the container(keyedBy: ) method, which is never called.

A reproducible case is available at, and attached to this issue.

To reproduce:

  1. Open the Crash/Crash.xcodeproject project with Xcode 11.2 beta 2

  2. Run the app in an iOS simulator

  3. Expected: the app crashes with a "not implemented" fatal error

  4. Actual: the app crashes before the "not implemented" fatal error

Experiments reveal that the bug does not reproduce when the encoder is not generic.

Experiments reveal that the bug does not reproduce when the encoder is invoked from another swift package (run `swift build` and then `.build/debug/Crash` in order to see the expected "not implemented" fatal error, and not the unexpected crash.

This issue was first reported in groue/GRDB.swift#636

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@groue groue commented Oct 20, 2019

Cross-posted on Apple Feedback Assistant, since this may be an Xcode issue: FB7395337

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@swift-ci swift-ci commented Nov 1, 2019

Comment by Randy R (JIRA)

We found a workaround. Setting DEAD_CODE_STRIPPING = NO in our app’s target fixes the crash.

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@swift-ci swift-ci commented Dec 6, 2019

Comment by Caleb J (JIRA)


I'm also seeing this problem in Version 11.2.1 (11B500) Latest Mac AppStore Release. Setting `DEAD_CODE_STRIPPING=NO` also worked for me.

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