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[SR-11259] Subscript-assigning a Data object retrieved from splitting another one crashes the application #3394

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ffried opened this issue Aug 5, 2019 · 1 comment
Open

[SR-11259] Subscript-assigning a Data object retrieved from splitting another one crashes the application #3394

ffried opened this issue Aug 5, 2019 · 1 comment
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bug Foundation

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@ffried
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ffried commented Aug 5, 2019

Previous ID SR-11259
Radar None
Original Reporter @ffried
Type Bug
Environment

Xcode 10.3:
Apple Swift version 5.0.1 (swiftlang-1001.0.82.4 clang-1001.0.46.5)
Target: x86_64-apple-darwin18.7.0

Xcode 11:
Apple Swift version 5.1 (swiftlang-1100.0.266.1 clang-1100.0.32.1)
Target: x86_64-apple-darwin18.7.0

Xcode 12.2:
Apple Swift version 5.3.1 (swiftlang-1200.0.41 clang-1200.0.32.8)
Target: x86_64-apple-darwin20.1.0

Additional Detail from JIRA
Votes 0
Component/s Foundation
Labels Bug
Assignee None
Priority Medium

md5: 263244286731725b695bee9ab16124cf

Issue Description:

The following Swift code crashes at runtime:

import Foundation
extension Data {
   mutating func modify() {
      for (i, byte) in enumerated() {
         switch byte {
         case 0x2D: self[i] = 0x2B // '-' -> '+'
         default: break
         }
      }
   }
}
let data = Data("ey-LCJ1.z7n-unids".utf8)
let parts = data.split(separator: 0x2E) // dot
var mutable = parts[1] // index 0 works
mutable.modify()

Output:

Stack dump:
0.  Program arguments: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -interpret s5_modifiedDataSlice.swift -enable-objc-interop -sdk /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -color-diagnostics -module-name s5_modifiedDataSlice 
0  swift                    0x0000000104525ee3 PrintStackTraceSignalHandler(void*) + 51
1  swift                    0x00000001045256bc SignalHandler(int) + 348
2  libsystem_platform.dylib 0x00007fff6e62bb5d _sigtramp + 29
3  libsystem_platform.dylib 0x0000000105aae080 _sigtramp + 2538087744
4  libswiftFoundation.dylib 0x00007fff6df84849 $s10Foundation4DataVys5UInt8VSicis + 9
5  libswiftFoundation.dylib 0x0000000105ae6425 $s10Foundation4DataVys5UInt8VSicis + 2545294309
6  libswiftFoundation.dylib 0x0000000105ae61d4 $s10Foundation4DataVys5UInt8VSicis + 2545293716
7  swift                    0x0000000100dbd50d llvm::MCJIT::runFunction(llvm::Function*, llvm::ArrayRef<llvm::GenericValue>) + 365
8  swift                    0x0000000100dc38e2 llvm::ExecutionEngine::runFunctionAsMain(llvm::Function*, std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&, char const* const*) + 1090
9  swift                    0x000000010038c6e1 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 58929
10 swift                    0x000000010037a7de swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 6862
11 swift                    0x000000010031887e main + 1246
12 libdyld.dylib            0x00007fff6e4403d5 start + 1
fish: 'swift s5_modifiedDataSlice.swift' terminated by signal SIGILL (Illegal instruction)

Update (2020-11-30)

After @belkadan's comment, I've modified the code to use indices instead of enumerated. The crash still occurs:

import Foundation

extension Data {
   mutating func modify() {
      for idx in indices {
         switch self[idx] {
            case 0x2D: self[idx] = 0x2B // '-' -> '+'
            default: break
         }
      }
   }
}

let data = Data("ey-LCJ1.z7n-unids".utf8)
let parts = data.split(separator: 0x2E, maxSplits: 2) // dot
print(parts.count) // -> 2
print(parts.indices) // => 0..<2
var mutable1 = parts[parts.startIndex]
mutable1.modify()
var mutable2 = parts[parts.endIndex]
mutable2.modify()
@belkadan
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Data's index doesn't always start at 0, so enumerated isn't really what you want. cc @phausler

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@shahmishal shahmishal transferred this issue from apple/swift May 5, 2022
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@belkadan @ffried