Upgrade to Swift 6 - Fix associated warnings

Author: parkera

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version: 5.9
+// swift-tools-version: 6.0
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
@@ -67,6 +67,7 @@ let interfaceBuildSettings: [CSetting] = [
 let swiftBuildSettings: [SwiftSetting] = [
     .define("DEPLOYMENT_RUNTIME_SWIFT"),
     .define("SWIFT_CORELIBS_FOUNDATION_HAS_THREADS"),
+    .swiftLanguageVersion(.v6),
     .unsafeFlags([
         "-Xfrontend",
         "-require-explicit-sendable",
@@ -146,7 +147,7 @@ let package = Package(
             exclude: [
                 "CMakeLists.txt"
             ],
-            swiftSettings:swiftBuildSettings
+            swiftSettings: swiftBuildSettings
         ),
         .target(
             name: "CoreFoundation",
@@ -207,6 +208,9 @@ let package = Package(
             ],
             exclude: [
                 "CMakeLists.txt"
+            ],
+            swiftSettings: [
+                .swiftLanguageVersion(.v6)
             ]
         ),
         .executableTarget(
@@ -215,6 +219,9 @@ let package = Package(
                 "Foundation",
                 "FoundationXML",
                 "FoundationNetworking"
+            ],
+            swiftSettings: [
+                .swiftLanguageVersion(.v6)
             ]
         ),
         .target(
@@ -241,7 +248,8 @@ let package = Package(
                 .copy("Foundation/Resources")
             ],
             swiftSettings: [
-                .define("NS_FOUNDATION_ALLOWS_TESTABLE_IMPORT")
+                .define("NS_FOUNDATION_ALLOWS_TESTABLE_IMPORT"),
+                .swiftLanguageVersion(.v6)
             ]
         ),
     ]

Sources/CoreFoundation/CFPlatform.c

@@ -1814,6 +1814,7 @@ CF_CROSS_PLATFORM_EXPORT int _CFThreadSetName(_CFThreadRef thread, const char *_
 #endif
 }
 
+// `buf` must be null-terminated
 CF_CROSS_PLATFORM_EXPORT int _CFThreadGetName(char *buf, int length) {
 #if SWIFT_CORELIBS_FOUNDATION_HAS_THREADS
 #if TARGET_OS_MAC

Sources/CoreFoundation/include/ForSwiftFoundationOnly.h

@@ -334,10 +334,10 @@ struct _NSCFXMLBridgeUntyped {
     void *kCFErrorLocalizedDescriptionKey;
 };
 
-CF_EXPORT struct _NSCFXMLBridgeStrong __NSCFXMLBridgeStrong;
-CF_EXPORT struct _NSCFXMLBridgeUntyped __NSCFXMLBridgeUntyped;
+CF_EXPORT struct _NSCFXMLBridgeStrong __NSCFXMLBridgeStrong __attribute__((swift_attr("nonisolated(unsafe)")));
+CF_EXPORT struct _NSCFXMLBridgeUntyped __NSCFXMLBridgeUntyped __attribute__((swift_attr("nonisolated(unsafe)")));
 
-CF_EXPORT struct _CFSwiftBridge __CFSwiftBridge;
+CF_EXPORT struct _CFSwiftBridge __CFSwiftBridge __attribute__((swift_attr("nonisolated(unsafe)")));
 
 CF_EXPORT void *_Nullable _CFSwiftRetain(void *_Nullable t);
 CF_EXPORT void _CFSwiftRelease(void *_Nullable t);
@@ -406,7 +406,7 @@ typedef void *_CFThreadSpecificKey;
 #endif
 
 CF_CROSS_PLATFORM_EXPORT Boolean _CFIsMainThread(void);
-CF_EXPORT _CFThreadRef _CFMainPThread;
+CF_EXPORT _CFThreadRef _CFMainPThread __attribute__((swift_attr("nonisolated(unsafe)")));
 
 CF_EXPORT CFHashCode __CFHashDouble(double d);
 

Sources/Foundation/Bridging.swift

@@ -222,7 +222,7 @@ internal final class __SwiftValue : NSObject, NSCopying {
         return __SwiftValue(value)
     }
 
-    public static let null: AnyObject = NSNull()
+    public static nonisolated(unsafe) let null: AnyObject = NSNull()
 
     override var description: String { String(describing: value) }
 }

Sources/Foundation/Bundle.swift

@@ -34,7 +34,7 @@ open class Bundle: NSObject, @unchecked Sendable {
         #endif
     }
 
-    private static var _mainBundle : Bundle = {
+    private static let _mainBundle : Bundle = {
         return Bundle(cfBundle: CFBundleGetMainBundle())
     }()
 

Sources/Foundation/DateIntervalFormatter.swift

@@ -83,18 +83,15 @@ internal extension _CFDateIntervalFormatterBoundaryStyle {
 // DateIntervalFormatter returns nil and NO for all methods in Formatter.
 
 open class DateIntervalFormatter: Formatter, @unchecked Sendable {
-    private let _core: AnyObject
-    private final var core: CFDateIntervalFormatter {
-        get { unsafeBitCast(_core, to: CFDateIntervalFormatter.self) }
-    }
+    private let core: CFDateIntervalFormatter
 
     public override init() {
-        _core = CFDateIntervalFormatterCreate(nil, nil, kCFDateIntervalFormatterShortStyle, kCFDateIntervalFormatterShortStyle)
+        core = CFDateIntervalFormatterCreate(nil, nil, kCFDateIntervalFormatterShortStyle, kCFDateIntervalFormatterShortStyle)
         super.init()
     }
 
     private init(cfFormatter: CFDateIntervalFormatter) {
-        self._core = cfFormatter
+        self.core = cfFormatter
         super.init()
     }
 
@@ -120,7 +117,7 @@ open class DateIntervalFormatter: Formatter, @unchecked Sendable {
                                                           object(of: NSLocale.self, from: coder, forKey: "NS.locale")?._cfObject,
                                                           object(of: NSCalendar.self, from: coder, forKey: "NS.calendar")?._cfObject,
                                                           object(of: NSTimeZone.self, from: coder, forKey: "NS.timeZone")?._cfObject)
-        self._core = core
+        self.core = core
 
         super.init(coder: coder)
     }

Sources/Foundation/FileHandle.swift

@@ -738,31 +738,31 @@ open class FileHandle : NSObject, @unchecked Sendable {
 
 extension FileHandle {
 
-    internal static var _stdinFileHandle: FileHandle = {
+    internal static let _stdinFileHandle: FileHandle = {
         return FileHandle(fileDescriptor: STDIN_FILENO, closeOnDealloc: false)
     }()
 
     public class var standardInput: FileHandle {
         return _stdinFileHandle
     }
 
-    internal static var _stdoutFileHandle: FileHandle = {
+    internal static let _stdoutFileHandle: FileHandle = {
         return FileHandle(fileDescriptor: STDOUT_FILENO, closeOnDealloc: false)
     }()
 
     public class var standardOutput: FileHandle {
         return _stdoutFileHandle
     }
 
-    internal static var _stderrFileHandle: FileHandle = {
+    internal static let _stderrFileHandle: FileHandle = {
         return FileHandle(fileDescriptor: STDERR_FILENO, closeOnDealloc: false)
     }()
 
     public class var standardError: FileHandle {
         return _stderrFileHandle
     }
 
-    internal static var _nulldeviceFileHandle: FileHandle = {
+    internal static let _nulldeviceFileHandle: FileHandle = {
         class NullDevice: FileHandle, @unchecked Sendable {
             override var availableData: Data {
                 return Data()

Sources/Foundation/FileManager+POSIX.swift

@@ -14,6 +14,7 @@ internal func &(left: UInt32, right: mode_t) -> mode_t {
 #endif
 
 @_implementationOnly import CoreFoundation
+internal import Synchronization
 
 #if os(WASI)
 import WASILibc
@@ -27,6 +28,10 @@ internal var O_TRUNC: Int32 { _getConst_O_TRUNC() }
 internal var O_WRONLY: Int32 { _getConst_O_WRONLY() }
 #endif
 
+#if os(Linux)
+fileprivate let previousStatxFailed = Mutex(false)
+#endif
+
 @_implementationOnly import CoreFoundation
 
 extension FileManager {
@@ -257,7 +262,8 @@ extension FileManager {
         }
 
         return try _fileSystemRepresentation(withPath: path) { fsRep in
-            if supportsStatx {
+            let statxPreviouslyFailed = previousStatxFailed.withLock { $0 }
+            if supportsStatx && !statxPreviouslyFailed {
                 var statInfo = stat()
                 var btime = timespec()
                 let statxErrno = _stat_with_btime(fsRep, &statInfo, &btime)
@@ -266,7 +272,7 @@ extension FileManager {
                     case EPERM, ENOSYS:
                         // statx() may be blocked by a security mechanism (eg libseccomp or Docker) even if the kernel verison is new enough. EPERM or ENONSYS may be reported.
                         // Dont try to use it in future and fallthough to a normal lstat() call.
-                        supportsStatx = false
+                        previousStatxFailed.withLock { $0 = true }
                         return try _statxFallback(atPath: path, withFileSystemRepresentation: fsRep)
 
                     default:

Sources/Foundation/FileManager.swift

@@ -34,20 +34,20 @@ internal let NativeFSREncoding = String.Encoding.utf8.rawValue
 
 #if os(Linux)
 // statx() is only supported by Linux kernels >= 4.11.0
-internal var supportsStatx: Bool = {
+internal let supportsStatx: Bool = {
     let requiredVersion = OperatingSystemVersion(majorVersion: 4, minorVersion: 11, patchVersion: 0)
     return ProcessInfo.processInfo.isOperatingSystemAtLeast(requiredVersion)
 }()
 
 // renameat2() is only supported by Linux kernels >= 3.15
-internal var kernelSupportsRenameat2: Bool = {
+internal let kernelSupportsRenameat2: Bool = {
     let requiredVersion = OperatingSystemVersion(majorVersion: 3, minorVersion: 15, patchVersion: 0)
     return ProcessInfo.processInfo.isOperatingSystemAtLeast(requiredVersion)
 }()
 #endif
 
 // For testing only: this facility pins the language used by displayName to the passed-in language.
-private var _overriddenDisplayNameLanguages: [String]? = nil
+private nonisolated(unsafe) var _overriddenDisplayNameLanguages: [String]? = nil
 
 extension FileManager {
 

Sources/Foundation/Host.swift

@@ -70,7 +70,7 @@ open class Host: NSObject {
     internal var _names = [String]()
     internal var _addresses = [String]()
 
-    static internal let _current = Host(currentHostName(), .current)
+    static internal let _cachedCurrentHostName = currentHostName()
 
     internal init(_ info: String?, _ type: ResolveType) {
         _info = info
@@ -110,7 +110,7 @@ open class Host: NSObject {
     }
 
     open class func current() -> Host {
-        return _current
+        return Host(Self._cachedCurrentHostName, .current)
     }
 
     public convenience init(name: String?) {