[SR-9712] Swift 5 fails to recognise `thin` closure (assertion failure) #52150

dmcyk · 2019-01-20T11:24:03Z


Previous ID	SR-9712
Radar	rdar://problem/47446870
Original Reporter	@dmcyk
Type	Bug

Environment

Swift 5 - swift-5.0-DEVELOPMENT-SNAPSHOT-2019-01-18

Swift 4.2.1 - Xcode 10.1

Additional Detail from JIRA


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

md5: 5fd2a93f448c3abced4efaa73416b634

cloned from:

SR-9711 Swift 5 fails to inline closures across module boundaries

Issue Description:

Problem

There seems to be regression in Swift 5, where the compiler fails to recognise `thin` closure and crashes with failed assertion.
Whereas same code in Swift 4.2.1 compiles.

Code

Given module foo:

// foo.swift
import Foundation

public enum Foo<Success, Failure: Error> {

  case success(Success)

  case failure(Failure)

  @inline(__always)
  public func mapContext<T, NewSuccess>(
    _ context: inout T,
    _ transform: @convention(thin) (Success, inout T) -> NewSuccess
  ) -> Foo<NewSuccess, Failure> {
    switch self {
    case let .success(success):
      return .success(transform(success, &context))
    case let .failure(failure):
      return .failure(failure)
    }
  }
}

#if swift(>=5.0)
#else
extension Never: Error {}
#endif

and our client module:

// main.swift
import Foundation
import foo

#if swift(>=5.0)
dump("swift-5.0")
#else
dump("swift-4.2")
#endif

let val = Foo<Int, Never>.success(10)
var i = 0
val.mapContext(&i) {
  return $1
}

Compilation

$ swiftc -force-single-frontend-invocation -whole-module-optimization -emit-module-path foo.swiftmodule -O -emit-library -module-name foo foo.swift
$ swiftc -force-single-frontend-invocation -whole-module-optimization -emit-executable -I . -L . -O -lfoo -module-name repro main.swift

Client module compilation output

Swift 4.2

main.swift:13:5: warning: result of call to 'mapContext' is unused
val.mapContext(&i) {
    ^         ~~~~~~

Swift 5

main.swift:13:5: warning: result of call to 'mapContext' is unused
val.mapContext(&i) {
    ^         ~~~~~~
Assertion failed: (expectedFnType->getExtInfo().hasContext() && "conversion thunk will not be thin!"), function transformFunction, file /Users/buildnode/jenkins/workspace/oss-swift-5.0-package-osx/swift/lib/SILGen/SILGenPoly.cpp, line 3367.
Stack dump:
0.  Program arguments: /Library/Developer/Toolchains/swift-5.0-DEVELOPMENT-SNAPSHOT-2019-01-18-a.xctoolchain/usr/bin/swift -frontend -c main.swift -target x86_64-apple-darwin18.2.0 -enable-objc-interop -sdk /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -I . -O -color-diagnostics -module-name repro -o /var/folders/mc/pqh3yf651nx_p_m9jdhlt1f80000gn/T/repro-6eb494.o
0  swift                    0x00000001126a4808 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 40
1  swift                    0x00000001126a3a85 llvm::sys::RunSignalHandlers() + 85
2  swift                    0x00000001126a4e12 SignalHandler(int) + 258
3  libsystem_platform.dylib 0x00007fff5fc47b3d _sigtramp + 29
4  swift                    0x00000001139bbae5 cmark_strbuf__initbuf + 131208
5  libsystem_c.dylib        0x00007fff5fb051c9 abort + 127
6  libsystem_c.dylib        0x00007fff5facd868 basename_r + 0
7  swift                    0x000000010f3fcfee (anonymous namespace)::Transform::transform(swift::Lowering::ManagedValue, swift::Lowering::AbstractionPattern, swift::CanType, swift::Lowering::AbstractionPattern, swift::CanType, swift::Lowering::SGFContext) + 10734
8  swift                    0x000000010f3f9fab swift::Lowering::SILGenFunction::emitSubstToOrigValue(swift::SILLocation, swift::Lowering::ManagedValue, swift::Lowering::AbstractionPattern, swift::CanType, swift::Lowering::SGFContext) + 171
9  swift                    0x000000010f3896ed swift::Lowering::Conversion::emit(swift::Lowering::SILGenFunction&, swift::SILLocation, swift::Lowering::ManagedValue, swift::Lowering::SGFContext) const + 749
10 swift                    0x000000010f3892fe swift::Lowering::ConvertingInitialization::finishEmission(swift::Lowering::SILGenFunction&, swift::SILLocation, swift::Lowering::ManagedValue) + 94
11 swift                    0x000000010f3890e0 swift::Lowering::SILGenFunction::emitConvertedRValue(swift::SILLocation, swift::Lowering::Conversion const&, swift::Lowering::SGFContext, llvm::function_ref<swift::Lowering::ManagedValue (swift::Lowering::SILGenFunction&, swift::SILLocation, swift::Lowering::SGFContext)>) + 384
12 swift                    0x000000010f31bc42 swift::Lowering::ArgumentSource::getConverted(swift::Lowering::SILGenFunction&, swift::Lowering::Conversion const&, swift::Lowering::SGFContext) && + 114
13 swift                    0x000000010f354657 (anonymous namespace)::ArgEmitter::emit(swift::Lowering::ArgumentSource&&, swift::Lowering::AbstractionPattern) + 4055
14 swift                    0x000000010f354f4d (anonymous namespace)::ArgEmitter::emitExpanded(swift::Lowering::ArgumentSource&&, swift::Lowering::AbstractionPattern) + 685
15 swift                    0x000000010f3536f6 (anonymous namespace)::ArgEmitter::emit(swift::Lowering::ArgumentSource&&, swift::Lowering::AbstractionPattern) + 118
16 swift                    0x000000010f34cc50 (anonymous namespace)::ArgEmitter::emitTopLevel(swift::Lowering::ArgumentSource&&, swift::Lowering::AbstractionPattern) + 2784
17 swift                    0x000000010f360077 (anonymous namespace)::CallSite::emit(swift::Lowering::SILGenFunction&, swift::Lowering::AbstractionPattern, swift::CanTypeWrapper<swift::SILFunctionType>, (anonymous namespace)::ParamLowering&, llvm::SmallVectorImpl<swift::Lowering::ManagedValue>&, llvm::SmallVectorImpl<(anonymous namespace)::DelayedArgument>&, llvm::Optional<swift::ForeignErrorConvention> const&, swift::ImportAsMemberStatus) && + 1047
18 swift                    0x000000010f35f77c (anonymous namespace)::CallEmission::emitArgumentsForNormalApply(swift::CanTypeWrapper<swift::FunctionType>&, swift::Lowering::AbstractionPattern&, swift::CanTypeWrapper<swift::SILFunctionType>, llvm::Optional<swift::ForeignErrorConvention> const&, swift::ImportAsMemberStatus, llvm::SmallVectorImpl<swift::Lowering::ManagedValue>&, llvm::Optional<swift::SILLocation>&, swift::CanTypeWrapper<swift::FunctionType>&) + 1772
19 swift                    0x000000010f344496 (anonymous namespace)::CallEmission::apply(swift::Lowering::SGFContext) + 3094
20 swift                    0x000000010f343780 swift::Lowering::SILGenFunction::emitApplyExpr(swift::Expr*, swift::Lowering::SGFContext) + 2016
21 swift                    0x000000010f3ad7c0 swift::ASTVisitor<(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext>::visit(swift::Expr*, swift::Lowering::SGFContext) + 80
22 swift                    0x000000010f3a294e swift::Lowering::SILGenFunction::emitIgnoredExpr(swift::Expr*) + 1198
23 swift                    0x000000010f338084 swift::Lowering::SILGenModule::visitTopLevelCodeDecl(swift::TopLevelCodeDecl*) + 564
24 swift                    0x000000010f338896 swift::Lowering::SILGenModule::emitSourceFile(swift::SourceFile*) + 822
25 swift                    0x000000010f3397f3 swift::SILModule::constructSIL(swift::ModuleDecl*, swift::SILOptions&, swift::FileUnit*) + 371
26 swift                    0x000000010f339d00 swift::performSILGeneration(swift::ModuleDecl*, swift::SILOptions&) + 16
27 swift                    0x000000010eabea84 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 9332
28 swift                    0x000000010eabb57d swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3021
29 swift                    0x000000010ea6d49e main + 686
30 libdyld.dylib            0x00007fff5fa5ced9 start + 1
<unknown>:0: error: unable to execute command: Abort trap: 6
<unknown>:0: error: compile command failed due to signal 6 (use -v to see invocation)

The text was updated successfully, but these errors were encountered:

dmcyk · 2019-01-20T11:32:18Z

cc aschwaighofer@apple.com (JIRA User) could this be maybe related to #21933 ?

dmcyk · 2019-01-20T11:43:05Z

guess that PR isn't direct cause of it. I tried also snapshot from 01-05 and got same assertion crash

belkadan · 2019-01-23T04:46:55Z

We probably should have underscored thin a long time ago, but it's a little late now. @slavapestov, @jckarter, this look familiar?

jckarter · 2019-01-23T17:36:21Z

We should still underscore it because it hasn't worked and doesn't work. You can't use @convention(thin) unless you're a compiler engineer. Chances are good that you'd hit this exact same assertion, or a different assertion, in an asserts build of Swift 4.2, but because Xcode doesn't ship Swift with assertions enabled, it's instead quietly miscompiling.

dmcyk · 2019-01-24T20:13:01Z

I see. if that's known, expected then its fine for me if you want to close this ticket. I only run into it trying to investigate SR-9711.

dmcyk · 2019-07-13T12:42:53Z

@jckarter since, as you said, this isn't meant to be used, should I close this ticket?

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

AnthonyLatsis added the crash Bug: A crash, i.e., an abnormal termination of software label Dec 12, 2022

AnthonyLatsis removed the compiler crash label Apr 17, 2023

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[SR-9712] Swift 5 fails to recognise `thin` closure (assertion failure) #52150

[SR-9712] Swift 5 fails to recognise `thin` closure (assertion failure) #52150

dmcyk commented Jan 20, 2019

dmcyk commented Jan 20, 2019

dmcyk commented Jan 20, 2019

belkadan commented Jan 23, 2019

jckarter commented Jan 23, 2019

dmcyk commented Jan 24, 2019

dmcyk commented Jul 13, 2019

[SR-9712] Swift 5 fails to recognise thin closure (assertion failure) #52150

[SR-9712] Swift 5 fails to recognise thin closure (assertion failure) #52150

Comments

dmcyk commented Jan 20, 2019

Problem

Code

Compilation

Client module compilation output

Swift 4.2

Swift 5

dmcyk commented Jan 20, 2019

dmcyk commented Jan 20, 2019

belkadan commented Jan 23, 2019

jckarter commented Jan 23, 2019

dmcyk commented Jan 24, 2019

dmcyk commented Jul 13, 2019

[SR-9712] Swift 5 fails to recognise `thin` closure (assertion failure) #52150

[SR-9712] Swift 5 fails to recognise `thin` closure (assertion failure) #52150