Swift: Crash when printing `self.dynamicType` in a protocol extension constrained on Objective-C subclass

Originator:jp
Number:rdar://24173309 Date Originated:13-Jan-2016 11:56 AM
Status:Open Resolved:
Product:Developer Tools Product Version:Xcode-7.2 (7C68)
Classification:Crash/Hang/Data Loss Reproducible:Always
 
Summary:
Accessing `self.dynamicType` in a protocol extension constrained on Objective-C subclass in Swift causes a bad memory access.

Steps to Reproduce:
Run the following code:

```swift
import Foundation
// doesn't crash when subclassing a non-Objective-C class, or not subclassing
class Class1: NSObject, Protocol1 {}

protocol Protocol1 {}
// doesn't crash without the type constraint, or with a different constraint ('Self: Hashable')
extension Protocol1 where Self: Class1 {
    func printType() {
        print(self.dynamicType)
        // also crashes:
        // _ = String(self.dynamicType)
        // self.dynamicType.description()
    }
}

Class1().printType() // EXC_BAD_ACCESS
```

Expected Results:
Accessing `self.dynamicType` in a protocol extension constrained on Objective-C subclass in Swift should return the calling type.

Actual Results:
Accessing `self.dynamicType` in a protocol extension constrained on Objective-C subclass in Swift causes a bad memory access.

Regression:
N/A

Notes:
N/A

Comments

31-Jan-2017 10:19 AM

Interestingly, this appears to be fixed in swiftc but not when JITing it with swift with Xcode 8.3 beta 1:

` $ cat file.swift import Foundation

class Class1: NSObject, Protocol1 {}

protocol Protocol1 {} extension Protocol1 where Self: Class1 { func printType() { print(type(of: self)) } }

Class1().printType() $ /Applications/Xcode-8.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift file.swift 0 swift 0x00000001060a2677 PrintStackTraceSignalHandler(void*) + 39 1 swift 0x00000001060a1b26 SignalHandler(int) + 646 2 libsystem_platform.dylib 0x00007fffcf6e6bba sigtramp + 26 3 libsystemplatform.dylib 0x0000000100000001 sigtramp + 814847073 4 libswiftCore.dylib 0x000000010b6ccb31 swiftgetTypeName + 401 5 libswiftCore.dylib 0x000000010b58939c TTSgq5PGVs10TeeStreamSSVs7_Stdout_GS_SSS0s16TextOutputStreamsTFFs20adHocPrint_unlockedu0_R_s16TextOutputStreamrFTxVs6MirrorRq_12isDebugPrintSb_T_L_13printTypeNameu0_R_S_rfPMP_T_ + 28 6 libswiftCore.dylib 0x000000010b65d26b TTSfq4ngs_n_n_TTSgq5PGVs10_TeeStreamSSVs7_Stdout_GS_SSS0s16TextOutputStreamsTFs20adHocPrint_unlockedu0_R_s16TextOutputStreamrFTxVs6MirrorRq_12isDebugPrintSb_T_ + 907 7 libswiftCore.dylib 0x000000010b521168 TTSgq5PGVs10TeeStreamSSVs7_Stdout_GS_SSS0s16TextOutputStreamsTFs15print_unlockedu0_R_s16TextOutputStreamrFTxRq__T_ + 1624 8 libswiftCore.dylib 0x000000010b668ed1 TTSfq4ggs_gs_n___TTSgq5GVs10_TeeStreamSSVs7_Stdout_GS_SSS0s16TextOutputStreamsTFs6printuRxs16TextOutputStreamrFTGSaP__9separatorSS10terminatorSS2toRx_T__merged + 353 9 libswiftCore.dylib 0x000000010b668cca TTSfq4ggs_gs_n___TTSgq5GVs10_TeeStreamSSVs7_Stdout_GS_SSS0s16TextOutputStreamsTFs6printuRxs16TextOutputStreamrFTGSaP__9separatorSS10terminatorSS2toRx_T_ + 42 10 libswiftCore.dylib 0x000000010b6692fd TTSfq4ggs_gs_TFs5printFTGSaP9separatorSS10terminatorSS_T__merged + 189 11 libswiftCore.dylib 0x000000010b668d2d TTSfq4ggs_gs_TFs5printFTGSaP9separatorSS10terminatorSS_T_ + 45 12 libswiftCore.dylib 0x000000010b591bad TFs5printFTGSaP9separatorSS10terminatorSST_ + 29 13 libswiftCore.dylib 0x0000000107106206 TFs5printFTGSaP9separatorSS10terminatorSST_ + 4223092342 14 libswiftCore.dylib 0x0000000107106046 TFs5printFTGSaP9separatorSS10terminatorSST_ + 4223091894 15 swift 0x00000001034db0ff llvm::MCJIT::runFunction(llvm::Function*, llvm::ArrayRef) + 655 16 swift 0x00000001034e0d43 llvm::ExecutionEngine::runFunctionAsMain(llvm::Function*, std::1::vector<std::1::basic_string<char, std::__1::char_traits, std::__1::allocator >, std::1::allocator<std::1::basic_string<char, std::__1::char_traits, std::__1::allocator > > > const&, char const const) + 707 17 swift 0x0000000102fefa49 swift::RunImmediately(swift::CompilerInstance&, std::1::vector<std::1::basic_string<char, std::__1::char_traits, std::__1::allocator >, std::1::allocator<std::1::basic_string<char, std::__1::char_traits, std::__1::allocator > > > const&, swift::IRGenOptions&, swift::SILOptions const&) + 3385 18 swift 0x0000000102fc5c4c swift::performFrontend(llvm::ArrayRef, char const*, void, swift::FrontendObserver) + 50572 19 swift 0x0000000102f734bc main + 9052 20 libdyld.dylib 0x00007fffcf4d9255 start + 1 Stack dump: 0. Program arguments: /Applications/Xcode-8.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -interpret file.swift -enable-objc-interop -sdk /Applications/Xcode-8.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -color-diagnostics -module-name file [1] 31014 segmentation fault file.swift $ /Applications/Xcode-8.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swiftc file.swift -sdk /Applications/Xcode-8.3.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk $ ./file Class1 `

By jp at Jan. 31, 2017, 6:22 p.m. (reply...)

Did we ever get a workaround or response on this issue?

By AnthonyMDev at Feb. 22, 2016, 7:58 p.m. (reply...)

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