Fixed segmentation fault crash (#1198)

* Fixed glob segmentation fault

* Renamed AtomicDictionary to ThreadSafeDictionary

* Refactored ThreadSafeDictionary

* ThreadSafeDictionary replaced with ThreadSafeContainer

* Removed reader/writer

* ThreadSafeContainer replaced with Atomic

CHANGELOG.md

@@ -8,6 +8,7 @@
 ### Fixed
 
 - Fix Monterey macOS shell version, shell login flag for environments [#1167](https://github.com/yonaskolb/XcodeGen/issues/1167) @bimawa
+- Fixed crash caused by a simultaneous write during a glob processing [#1177](https://github.com/yonaskolb/XcodeGen/issues/1177) @tr1ckyf0x
 
 ## 2.27.0
 

Sources/XcodeGenCore/Atomic.swift

@@ -8,20 +8,45 @@
 import Foundation
 
 @propertyWrapper
-struct Atomic<Value> {
-    private let queue = DispatchQueue(label: "com.xcodegencore.atomic")
+public final class Atomic<Value> {
+
     private var value: Value
 
-    init(wrappedValue: Value) {
+    private let queue = DispatchQueue(
+        label: "com.xcodegencore.atomic.\(UUID().uuidString)",
+        qos: .utility,
+        attributes: .concurrent,
+        autoreleaseFrequency: .inherit,
+        target: .global()
+    )
+
+    public init(wrappedValue: Value) {
         self.value = wrappedValue
     }
 
-    var wrappedValue: Value {
+    public var wrappedValue: Value {
         get {
-            return queue.sync { value }
+            queue.sync { value }
         }
         set {
-            queue.sync { value = newValue }
+            queue.async(flags: .barrier) { [weak self] in
+                self?.value = newValue
+            }
+        }
+    }
+
+    /// Allows us to get the actual `Atomic` instance with the $
+    /// prefix.
+    public var projectedValue: Atomic<Value> {
+        return self
+    }
+
+    /// Modifies the protected value using `closure`.
+    public func with<R>(
+        _ closure: (inout Value) throws -> R
+    ) rethrows -> R {
+        try queue.sync(flags: .barrier) {
+            try closure(&value)
         }
     }
 }

Sources/XcodeGenCore/Glob.swift

@@ -198,13 +198,17 @@ public class Glob: Collection {
 
         var isDirectoryBool = ObjCBool(false)
         let isDirectory = FileManager.default.fileExists(atPath: path, isDirectory: &isDirectoryBool) && isDirectoryBool.boolValue
-        isDirectoryCache[path] = isDirectory
+        $isDirectoryCache.with { isDirectoryCache in
+            isDirectoryCache[path] = isDirectory
+        }
 
         return isDirectory
     }
 
     private func clearCaches() {
-        isDirectoryCache.removeAll()
+        $isDirectoryCache.with { isDirectoryCache in
+            isDirectoryCache.removeAll()
+        }
     }
 
     private func paths(usingPattern pattern: String, includeFiles: Bool) -> [String] {

Tests/XcodeGenCoreTests/AtomicTests.swift

@@ -0,0 +1,39 @@
+//
+//  AtomicTests.swift
+//  
+//
+//  Created by Vladislav Lisianskii on 27.03.2022.
+//
+
+import XCTest
+@testable import XcodeGenCore
+
+final class AtomicTests: XCTestCase {
+
+    @Atomic private var atomicDictionary = [String: Int]()
+
+    func testSimultaneousWriteOrder() {
+        let group = DispatchGroup()
+
+        for index in (0..<100) {
+            group.enter()
+            DispatchQueue.global().async {
+                self.$atomicDictionary.with { atomicDictionary in
+                    atomicDictionary["\(index)"] = index
+                }
+                group.leave()
+            }
+        }
+
+        group.notify(queue: .main, execute: {
+            var expectedValue = [String: Int]()
+            for index in (0..<100) {
+                expectedValue["\(index)"] = index
+            }
+            XCTAssertEqual(
+                self.atomicDictionary,
+                expectedValue
+            )
+        })
+    }
+}