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[SR-9903] Segmentation Fault: Malformed KeyPath Code #52309

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daveanderson mannequin opened this issue Feb 11, 2019 · 2 comments
Closed

[SR-9903] Segmentation Fault: Malformed KeyPath Code #52309

daveanderson mannequin opened this issue Feb 11, 2019 · 2 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself

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@daveanderson
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Mannequin

daveanderson mannequin commented Feb 11, 2019

Previous ID SR-9903
Radar None
Original Reporter @daveanderson
Type Bug
Status Closed
Resolution Done
Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug
Assignee None
Priority Medium

md5: 54eb1c2206f79ed0432e7c5e05e21ff2

Issue Description:

While experimenting with an idea using KeyPaths (which I've not heavily used previously) the Swift compiler (4.2, Xcode 10.1) began crashing with the following stack trace:

0  swift                    0x0000000105f6e59a PrintStackTraceSignalHandler(void*) + 42
1  swift                    0x0000000105f6dd4e SignalHandler(int) + 302
2  libsystem_platform.dylib 0x00007fff6ea24b3d _sigtramp + 29
3  libsystem_platform.dylib 000000000000000000 _sigtramp + 2438837472
4  swift                    0x0000000102c5ca4c (anonymous namespace)::SILGenWitnessTable<(anonymous namespace)::SILGenConformance>::addMethod(swift::SILDeclRef) + 60
5  swift                    0x0000000102c5c934 swift::SILWitnessVisitor<(anonymous namespace)::SILGenConformance>::visitAbstractStorageDecl(swift::AbstractStorageDecl*) + 52
6  swift                    0x0000000102c5beb5 swift::SILWitnessVisitor<(anonymous namespace)::SILGenConformance>::visitProtocolDecl(swift::ProtocolDecl*) + 741
7  swift                    0x0000000102c5b66c swift::Lowering::SILGenModule::getWitnessTable(swift::ProtocolConformance*) + 364
8  swift                    0x0000000102c5fcbb swift::Lowering::SILGenModule::visitExtensionDecl(swift::ExtensionDecl*) + 587
9  swift                    0x0000000102b791eb swift::Lowering::SILGenModule::emitSourceFile(swift::SourceFile*, unsigned int) + 939
10 swift                    0x0000000102b7ada5 swift::SILModule::constructSIL(swift::ModuleDecl*, swift::SILOptions&, swift::FileUnit*, llvm::Optional<unsigned int>, bool) + 1333
11 swift                    0x00000001021fb36e performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 28990
12 swift                    0x00000001021f0d35 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 7717
13 swift                    0x0000000102196965 main + 1349
14 libdyld.dylib            0x00007fff6e839ed9 start + 1
Stack dump:

It took me a few minutes to figure out the file of my source code that was the cause of the error and after doing some more reading on KeyPaths I discovered I wasn't satisfying the requirements of the generics associated with KeyPaths.

While I was able to work around the seg fault, the compiler does not seem robust in this area. I received no diagnostic messaging, only the unceremonious crash.

While I'm not in a position to share my source code (which I have subsequently changed significantly), I believe the offending code was

public protocol KeyPathIdentifiable {
    typealias KeyPathStringIdentifier = (KeyPath, String)
    typealias KeyPathDateIdentifier = (KeyPath, Date)
    typealias KeyPathIdentifier = (KeyPath, Comparable)
    typealias KeyPathIdentifierCombination = [[KeyPathIdentifier]]

    var keyPathIdentifier: [KeyPathIdentifierCombination] { get }
}

I can replicate the crash by adding this snippet to my project. (I now understand why this code is wrong, it's just unfortunate that it causes a crash.)

No, I have not tried this with the Swift 5 compiler.

Here is one other compiler stack traces from my project build history related to efforts in this area.

0  swift                    0x000000010be6259a PrintStackTraceSignalHandler(void*) + 42
1  swift                    0x000000010be61d4e SignalHandler(int) + 302
2  libsystem_platform.dylib 0x00007fff6ea24b3d _sigtramp + 29
3  libsystem_platform.dylib 000000000000000000 _sigtramp + 2438837472
4  swift                    0x000000010934b35e swift::serialization::Serializer::writeDecl(swift::Decl const*) + 72990
5  swift                    0x0000000109370b6f swift::serialization::Serializer::writeAllDeclsAndTypes() + 87183
6  swift                    0x00000001093896b6 swift::serialization::Serializer::writeAST(llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, bool) + 5030
7  swift                    0x00000001093975df swift::serialization::Serializer::writeToStream(llvm::raw_ostream&, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::SILModule const*, swift::SerializationOptions const&) + 4271
8  swift                    0x000000010939b475 void llvm::function_ref<void (llvm::raw_ostream&)>::callback_fn<swift::serialize(llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::SerializationOptions const&, swift::SILModule const*)::$_4>(long, llvm::raw_ostream&) + 181
9  swift                    0x000000010939b6bb withOutputFile(swift::ASTContext&, llvm::StringRef, llvm::function_ref<void (llvm::raw_ostream&)>) + 571
10 swift                    0x000000010939b2a3 swift::serialize(llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::SerializationOptions const&, swift::SILModule const*) + 275
11 swift                    0x00000001080fd43e std::__1::__function::__func<performCompileStepsPostSILGen(swift::CompilerInstance&, swift::CompilerInvocation&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule> >, bool, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::PrimarySpecificPaths const&, bool, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*)::$_10, std::__1::allocator<performCompileStepsPostSILGen(swift::CompilerInstance&, swift::CompilerInvocation&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule> >, bool, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::PrimarySpecificPaths const&, bool, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*)::$_10>, void ()>::operator()() + 526
12 swift                    0x00000001080f1e36 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 39942
13 swift                    0x00000001080e4d35 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 7717
14 swift                    0x000000010808a965 main + 1349
15 libdyld.dylib            0x00007fff6e839ed9 start + 1
Stack dump:
@belkadan
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It is in fact fixed in Swift 5!

<stdin>:4:42: error: reference to generic type 'KeyPath' requires arguments in <...>
    typealias KeyPathStringIdentifier = (KeyPath, String)
                                         ^
                                                <Any, Any>
Swift.KeyPath:1:14: note: generic type 'KeyPath' declared here
public class KeyPath<Root, Value> : PartialKeyPath<Root> {
             ^
<stdin>:5:40: error: reference to generic type 'KeyPath' requires arguments in <...>
    typealias KeyPathDateIdentifier = (KeyPath, Date)
                                       ^
                                              <Any, Any>
Swift.KeyPath:1:14: note: generic type 'KeyPath' declared here
public class KeyPath<Root, Value> : PartialKeyPath<Root> {
             ^
<stdin>:6:36: error: reference to generic type 'KeyPath' requires arguments in <...>
    typealias KeyPathIdentifier = (KeyPath, Comparable)
                                   ^
                                          <Any, Any>
Swift.KeyPath:1:14: note: generic type 'KeyPath' declared here
public class KeyPath<Root, Value> : PartialKeyPath<Root> {
             ^

@daveanderson
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daveanderson mannequin commented Feb 12, 2019

Thanks for the confirmation. I attempted to validate the improved error messaging in my project but unfortunately I encountered https://bugs.swift.org/browse/SR-9910 in the process.

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