Segmentation fault in Linux with Swift 5.4 when using Grand Central Dispatch

Using Swift
, ,
1

Here's one that has me stumped. The following code runs just fine under MacOS but causes a Segmentation fault under Linux. Under both systems I'm using Swift 5.4.

Linux is running Ubuntu 20.

Any thoughts? If I change the code to use the Thread class then it's fine.

import Foundation
import CoreFoundation

let queue: DispatchQueue = DispatchQueue(label: UUID().uuidString, qos: .utility, attributes: .concurrent)
let group: DispatchGroup = DispatchGroup()
let proc:  Process       = Process()

proc.executableURL = URL(fileURLWithPath: "/usr/bin/iconv")
proc.arguments = [ "-l" ]
proc.standardError = Pipe()
proc.standardOutput = Pipe()

do {
    try proc.run()
}
catch let e {
    try? "\(e)".write(toFile: "/dev/stderr", atomically: false, encoding: String.Encoding.utf8)
}

var _stderr: String = ""
var _stdout: String = ""

queue.async(group: group) { _stderr = String(data: (proc.standardError! as! Pipe).fileHandleForReading.readDataToEndOfFile(), encoding: String.Encoding.utf8) ?? "" }
queue.async(group: group) { _stdout = String(data: (proc.standardOutput! as! Pipe).fileHandleForReading.readDataToEndOfFile(), encoding: String.Encoding.utf8) ?? "" }
queue.async(group: group) { proc.waitUntilExit() }
group.wait()

// DOES NOT GET TO THIS PART ON LINUX!

sleep(10)

print("stdout: \(_stdout)")
print("stderr: \(_stderr)")
print("Results: \(proc.terminationStatus)")