/SampleProject

Primary LanguageSwift

Debug Compiler Directives in Swift Package cause Runtime Crash

This sample project provides a setup to reproduce a crash when using #if DEBUG directives in a Swift Package that is linked (but not embedded) to a release build of a static library. If the static library and the Package's library target are embedded into an App a runtime crash occurs.

If the App target is also build in release, the crash doesn't occur.

Project Setup

The SampleProject consists of:

  • an App Target called SampleApp
  • a Framework Target called SampleFramework
  • a local Swift Package called SamplePackage

The Dependency Graph looks like this:

SampleApp
└── embeds SampleFramework
    └── links to SamplePackage
└── embeds SamplePackage

If you start the Project after checkout, everything builds and runs, because SampleFramework has been added to SampleApp's Frameworks, Libraries, and Embedded Content (Screenshot) via Xcode. SampleFramework only adds SamplePackage as a Target Dependency (Screenshot), but it doesn't embed it (the App does).

Reproduce the Crash

To reproduce the crash we do the following steps:

  1. Compile SampleFramework in Release configuration Compiling Framework in Release Mode

  2. Remove the previous SampleFramework from our SampleApp's Frameworks, Libraries, and Embedded Content

  3. Select the SampleFramework binary from Products in the project navigator and open it in Finder Show binary framework in build directory

  4. Add the binary from Release-iphonesimulator/SampleFramework.framework/SampleFramework to SampleApp's Frameworks, Libraries, and Embedded Content Add binary framework to App

  5. Select the SampleApp scheme (make sure it's in Debug configuration) and run it again

  6. Upon launch the project crashes Image of Crash

Crash Details

Message: EXC_BAD_ACCESS (code=1, address=0xfffffffffffffff0) Crashlog:

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0xfffffffffffffff0
Exception Codes: 0x0000000000000001, 0xfffffffffffffff0
VM Region Info: 0xfffffffffffffff0 is not in any region.  Bytes after previous region: 18446638520056414193  
      REGION TYPE                    START - END         [ VSIZE] PRT/MAX SHRMOD  REGION DETAIL
      MALLOC_NANO (reserved)   600018000000-600020000000 [128.0M] rw-/rwx SM=NUL  ...(unallocated)
--->  
      UNUSED SPACE AT END
Termination Reason: SIGNAL 11 Segmentation fault: 11
Terminating Process: exc handler [50054]

Triggered by Thread:  0

Thread 0 Crashed::  Dispatch queue: com.apple.main-thread
0   libswiftCore.dylib            	       0x18bf8620c _swift_release_dealloc + 16
1   libswiftCore.dylib            	       0x18bf86df4 bool swift::RefCounts<swift::RefCountBitsT<(swift::RefCountInlinedness)1>>::doDecrementSlow<(swift::PerformDeinit)1>(swift::RefCountBitsT<(swift::RefCountInlinedness)1>, unsigned int) + 128
2   SampleApp                     	       0x100c4de3c outlined destroy of SampleView + 36
3   SampleApp                     	       0x100c4da60 closure #1 in SampleAppApp.body.getter + 108 (SampleApp.swift:15)
4   SwiftUI                       	       0x105cd1b6c 0x1050d4000 + 12573548
5   SampleApp                     	       0x100c4d900 SampleAppApp.body.getter + 144 (SampleApp.swift:14)
6   SampleApp                     	       0x100c4dd98 protocol witness for App.body.getter in conformance SampleAppApp + 12

Complete Crashlog

Hints

This crash does only occur when the #if DEBUG directives are present in SamplePackage/Sources/SamplePackage/HelloWorld.swift. Removing them and building a new SampleFramework (repeating the steps above) fixes the issue.

If both SampleApp and SampleFramework are compiled with the same build configuration (release or debug) the issue also doesn't come up.