App launched with `--justlaunch` immediately crashes when trying to print to stdout

[hamchapman]

Expected behavior

The app can print to stdout without the app crashing.

Actual behavior.

The app immediately crashes when attempting to write to stdout.

Steps to reproduce the problem

See steps in this repo, otherwise:

1. Create a new iOS app.
2. Update App.swift (or equivalent) to look like this:

import SwiftUI

@main
struct iOSDeployCrashApp: App {

    init() {
        FileHandle.standardOutput.write("crash causer".data(using: .utf8)!)
    }

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

3. Build the iOS app using a command like this (replacing the project and scheme names as appropriate):

xcodebuild -derivedDataPath ios/DerivedData -project ios-deploy-stdout-crash/ios-deploy-stdout-crash.xcodeproj -scheme ios-deploy-stdout-crash -destination generic/platform=iOS

4. Launch the app using ios-deploy like this (again, replacing the id and bundle path as appropriate):

ios-deploy \
  --id "00008030-XXXXXXXXXXXXX" \
  --bundle "ios/DerivedData/Build/Products/Debug-iphoneos/ios-deploy-stdout-crash.app" \
  --justlaunch

Commentary on the issue

This seems to be related to the timing between when:

• the process detaches (because of the --justlaunch flag), and
• the iOS app first tries to print to stdout (see App.swift)

The app will not crash if you do any of the following:

• comment out the line where the app tries to write to stdout, or
• launch the app via a method other than ios-deploy
• launch the app via ios-deploy without the --justlaunch flag
• use a build of ios-deploy that adds a time.sleep(10) call above this line

Note that if you use Xcode 15 and a device running iOS 17 and use devicectl then the crash does not occur, so I am confident that it's something to do with what ios-deploy is doing in terms of stdout/stderr.

The actual error that ends up getting thrown is errno 5 (EIO).

Maybe it's something to do with how the process is being detached and the state of the various pipes involved at that point?

System Specs

Please run the commands below in your Terminal.app and include it in the issue. Check when done and include results below.

• 1. system_profiler SPSoftwareDataType

  Software:
  
      System Software Overview:
  
        System Version: macOS 13.6 (22G120)
        Kernel Version: Darwin 22.6.0
        Boot Volume: Macintosh HD
        Boot Mode: Normal
        Computer Name: DTO-A026
        User Name: Ham Chapman (ham)
        Secure Virtual Memory: Enabled
        System Integrity Protection: Enabled
        Time since boot: 3 days, 18 hours, 14 minutes
  

• 2. ios-deploy -V: 1.12.2
• 3. xcodebuild -version: /Applications/Xcode-14.3.1.app/Contents/Developer
• 4. xcode-select --print-path

   Xcode 14.3.1
   Build version 14E300c
  

• 5. gcc --version:

  Apple clang version 14.0.3 (clang-1403.0.22.14.1)
  Target: arm64-apple-darwin22.6.0
  Thread model: posix
  InstalledDir: /Applications/Xcode-14.3.1.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
  

• 6. lldb --version:

  lldb-1403.0.17.67
  Apple Swift version 5.8.1 (swiftlang-5.8.0.124.5 clang-1403.0.22.11.100)
  

• If using NodeJS/npm: (N/A)
  • 7. npm -v
  • 8. node -v

[pothurajtharun]

Even I'm facing the same issue, before deatch the process it should wait for some time. Can someone please look into it ? Thanks!

[diegodorado]

Having the same issue