[SR-11098] swiftc segfault when compiling in release mode

[Frizlab]

Previous ID	SR-11098
Radar	rdar://52953078
Original Reporter	@Frizlab
Type	Bug
Status	Closed
Resolution	Duplicate

Environment

Tested on macOS with Swift 5.0.1 and 5.1 (swiftlang-1100.0.212.5 clang-1100.0.28.2), and on Linux with Swift 4.2.1.

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, CompilerCrash, OptimizedOnly
Assignee	None
Priority	Medium

md5: 39d19eb2ea75fefab810e98ddc4e4073

duplicates:

• SR-4206 Override checking does not properly enforce requirements

Issue Description:

The following project crashes when compiled with the the -c release option:

https://gitlab.com/frizlab-demo-projects/swift-erasure-crash

Here’s the stack dump.

Stack dump:
0.  Program arguments: /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -c /Users/frizlab/Desktop/test_crash/Sources/test_crash/ErasureChild.swift /Users/frizlab/Desktop/test_crash/Sources/test_crash/ErasureParent.swift /Users/frizlab/Desktop/test_crash/Sources/test_crash/Implementation.swift /Users/frizlab/Desktop/test_crash/Sources/test_crash/Protocol.swift /Users/frizlab/Desktop/test_crash/Sources/test_crash/main.swift -supplementary-output-file-map /var/folders/5j/7jfjtgkx7yg9qp9bpt33q0hm0000gn/T/supplementaryOutputs-b25cfc -target x86_64-apple-macosx10.10 -enable-objc-interop -sdk /Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk -I /Users/frizlab/Desktop/test_crash/.build/x86_64-apple-macosx/release -F /Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/Library/Frameworks -module-cache-path /Users/frizlab/Desktop/test_crash/.build/x86_64-apple-macosx/release/ModuleCache -swift-version 4.2 -O -D SWIFT_PACKAGE -color-diagnostics -module-name test_crash -num-threads 8 -o /Users/frizlab/Desktop/test_crash/.build/x86_64-apple-macosx/release/test_crash.build/ErasureChild.swift.o -o /Users/frizlab/Desktop/test_crash/.build/x86_64-apple-macosx/release/test_crash.build/ErasureParent.swift.o -o /Users/frizlab/Desktop/test_crash/.build/x86_64-apple-macosx/release/test_crash.build/Implementation.swift.o -o /Users/frizlab/Desktop/test_crash/.build/x86_64-apple-macosx/release/test_crash.build/Protocol.swift.o -o /Users/frizlab/Desktop/test_crash/.build/x86_64-apple-macosx/release/test_crash.build/main.swift.o 
1.  While emitting IR SIL function "@$s10test_crash9AnyParentC7unboxedxSgyAA0D8ProtocolRzlF".
 for 'unboxed()' (at /Users/frizlab/Desktop/test_crash/Sources/test_crash/ErasureParent.swift:29:9)
0  swift                    0x000000010c5c2c83 PrintStackTraceSignalHandler(void*) + 51
1  swift                    0x000000010c5c2456 SignalHandler(int) + 358
2  libsystem_platform.dylib 0x00007fff70ec7b5d _sigtramp + 29
3  swift                    0x00000001091b4e71 swift::Type::transformRec(llvm::function_ref<llvm::Optional<swift::Type> (swift::TypeBase*)>) const + 49
4  swift                    0x00000001083db137 swift::irgen::emitWitnessTableRef(swift::irgen::IRGenFunction&, swift::CanType, llvm::Value**, swift::ProtocolConformanceRef) + 311
5  swift                    0x00000001083e2d40 swift::irgen::emitGenericRequirementFromSubstitutions(swift::irgen::IRGenFunction&, swift::CanGenericSignature, swift::ModuleDecl&, swift::irgen::GenericRequirement, swift::SubstitutionMap) + 256
6  swift                    0x00000001083e2ba4 void llvm::function_ref<void (swift::irgen::GenericRequirement)>::callback_fn<(anonymous namespace)::EmitPolymorphicArguments::emit(swift::SubstitutionMap, swift::irgen::WitnessMetadata*, swift::irgen::Explosion&)::$_21>(long, swift::irgen::GenericRequirement) + 36
7  swift                    0x00000001083e0a3d void llvm::function_ref<void (swift::irgen::GenericRequirement)>::callback_fn<(anonymous namespace)::PolymorphicConvention::enumerateUnfulfilledRequirements(llvm::function_ref<void (swift::irgen::GenericRequirement)> const&)::$_11>(long, swift::irgen::GenericRequirement) + 205
8  swift                    0x00000001083e094f (anonymous namespace)::PolymorphicConvention::enumerateUnfulfilledRequirements(llvm::function_ref<void (swift::irgen::GenericRequirement)> const&) + 319
9  swift                    0x00000001083e2925 swift::irgen::emitPolymorphicArguments(swift::irgen::IRGenFunction&, swift::CanTypeWrapper<swift::SILFunctionType>, swift::SubstitutionMap, swift::irgen::WitnessMetadata*, swift::irgen::Explosion&) + 485
10 swift                    0x000000010846b503 (anonymous namespace)::IRGenSILFunction::visitFullApplySite(swift::FullApplySite) + 2019
11 swift                    0x000000010844bbfa swift::irgen::IRGenModule::emitSILFunction(swift::SILFunction*) + 9866
12 swift                    0x00000001082f9360 swift::irgen::IRGenerator::emitGlobalTopLevel() + 1616
13 swift                    0x00000001084267cc swift::performIRGeneration(swift::IRGenOptions&, swift::ModuleDecl*, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule> >, llvm::StringRef, swift::PrimarySpecificPaths const&, llvm::LLVMContext&, llvm::ArrayRef<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >, llvm::GlobalVariable**) + 1676
14 swift                    0x0000000108216da1 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 36993
15 swift                    0x000000010820a474 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 6868
16 swift                    0x0000000108198fb3 main + 1219
17 libdyld.dylib            0x00007fff70cdc3d5 start + 1
18 libdyld.dylib            0x0000000000000029 start + 2402434133

[theblixguy]

You can work around it in the meantime by disabling the speculative devirtualization optimisation pass:

swift build -c release -Xswiftc "-Xllvm" -Xswiftc "-sil-disable-pass=specdevirt"

I don't think this is a bug with specdevirt though, but possibly an optimisation pass before it. cc @eeckstein

[eeckstein]

cc aschwaighofer@apple.com (JIRA User)

[aschwaighofer]

The problem is in the source and that the type checker allows this:

We have a covariant generic parameter type in a method override. This should not type check.

public protocol ChildProtocol : ParentProtocol {
}

public class AnyParent : ParentProtocol {

  public func unboxed<ParentType : ParentProtocol>() -> ParentType? {
  }
}

public class AnyChild : AnyParent, ChildProtocol {
  
=>  public override func unboxed<ChildType : ChildProtocol>() -> ChildType? {
  }

[aschwaighofer]

Should be fixed by #24484

[Frizlab]

aschwaighofer@apple.com (JIRA User) Confirmed fixed in latest master nightly

[theblixguy]

Great

[Frizlab]

Done! Sorry I did not know I had to close the issue as it was already marked Resolved 🙂