Add FreeBSD support

This allows building Swift Build for FreeBSD hosts, as well as building for a FreeBSD target from a FreeBSD host.

Author: jakepetroules

Diff for: Package.swift

@@ -105,7 +105,7 @@ let package = Package(
                 "SWBBuildSystem",
                 "SWBServiceCore",
                 "SWBTaskExecution",
-                .product(name: "SystemPackage", package: "swift-system", condition: .when(platforms: [.linux, .android, .windows])),
+                .product(name: "SystemPackage", package: "swift-system", condition: .when(platforms: [.linux, .openbsd, .android, .windows, .custom("freebsd")])),
             ],
             exclude: ["CMakeLists.txt"],
             swiftSettings: swiftSettings(languageMode: .v5)),
@@ -197,8 +197,8 @@ let package = Package(
                 "SWBCSupport",
                 "SWBLibc",
                 .product(name: "ArgumentParser", package: "swift-argument-parser"),
-                .product(name: "Crypto", package: "swift-crypto", condition: .when(platforms: [.linux, .android])),
-                .product(name: "SystemPackage", package: "swift-system", condition: .when(platforms: [.linux, .android, .windows])),
+                .product(name: "Crypto", package: "swift-crypto", condition: .when(platforms: [.linux, .openbsd, .android, .custom("freebsd")])),
+                .product(name: "SystemPackage", package: "swift-system", condition: .when(platforms: [.linux, .openbsd, .android, .windows, .custom("freebsd")])),
             ],
             exclude: ["CMakeLists.txt"],
             swiftSettings: swiftSettings(languageMode: .v5)),
@@ -445,7 +445,7 @@ if useLocalDependencies {
     package.dependencies += [
         .package(url: "https://github.com/apple/swift-crypto.git", "2.0.0"..<"4.0.0"),
         .package(url: "https://github.com/swiftlang/swift-driver.git", branch: "main"),
-        .package(url: "https://github.com/apple/swift-system.git", .upToNextMajor(from: "1.4.1")),
+        .package(url: "https://github.com/apple/swift-system.git", .upToNextMajor(from: "1.4.2")),
         .package(url: "https://github.com/apple/swift-argument-parser.git", from: "1.0.3"),
     ]
     if !useLLBuildFramework {

Diff for: Sources/SWBCore/Core.swift

@@ -668,6 +668,6 @@ struct CoreRegistryDelegate : PlatformRegistryDelegate, SDKRegistryDelegate, Spe
 extension OperatingSystem {
     /// Whether the Core is allowed to create a fallback toolchain, SDK, and platform for this operating system in cases where no others have been provided.
     internal var createFallbackSystemToolchain: Bool {
-        return self == .linux
+        return self == .linux || self == .freebsd
     }
 }

Diff for: Sources/SWBCore/SDKRegistry.swift

@@ -623,7 +623,7 @@ public final class SDKRegistry: SDKRegistryLookup, CustomStringConvertible, Send
     private func fallbackSystemSDKSettings(operatingSystem: OperatingSystem) throws -> [String: PropertyListItem] {
         let defaultProperties: [String: PropertyListItem]
         switch operatingSystem {
-        case .linux:
+        case .linux, .freebsd:
             defaultProperties = [
                 // Workaround to avoid `-dependency_info` on Linux.
                 "LD_DEPENDENCY_INFO_FILE": .plString(""),

Diff for: Sources/SWBCore/Settings/Settings.swift

@@ -5292,6 +5292,8 @@ extension OperatingSystem {
                 return "windows"
             case .linux:
                 return "linux"
+            case .freebsd:
+                return "freebsd"
             case .android:
                 return "android"
             case .unknown:

Diff for: Sources/SWBGenericUnixPlatform/FreeBSDLibtool.xcspec

@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+(
+    {
+        Domain = freebsd;
+        Identifier = com.apple.pbx.linkers.libtool;
+        BasedOn = generic-unix:com.apple.pbx.linkers.libtool;
+        Type = Linker;
+        Options = (
+            {
+                Name = "LIBTOOL_USE_RESPONSE_FILE";
+                Type = Boolean;
+                DefaultValue = NO;
+            },
+        );
+    },
+)

Diff for: Sources/SWBGenericUnixPlatform/Plugin.swift

@@ -24,6 +24,9 @@ struct GenericUnixPlatformSpecsExtension: SpecificationsExtension {
     }
 
     func specificationDomains() -> [String: [String]] {
-        ["linux": ["generic-unix"]]
+        [
+            "linux": ["generic-unix"],
+            "freebsd": ["generic-unix"],
+        ]
     }
 }

Diff for: Sources/SWBTestSupport/RunDestinationTestSupport.swift

@@ -98,6 +98,8 @@ extension _RunDestinationInfo {
             windows
         case .linux:
             linux
+        case .freebsd:
+            freebsd
         case .android:
             android
         case .unknown:
@@ -259,6 +261,14 @@ extension _RunDestinationInfo {
         return .init(platform: "linux", sdk: "linux", sdkVariant: "linux", targetArchitecture: arch, supportedArchitectures: ["x86_64", "aarch64"], disableOnlyActiveArch: false)
     }
 
+    /// A run destination targeting FreeBSD generic device, using the public SDK.
+    package static var freebsd: Self {
+        guard let arch = Architecture.hostStringValue  else {
+            preconditionFailure("Unknown architecture \(Architecture.host.stringValue ?? "<nil>")")
+        }
+        return .init(platform: "freebsd", sdk: "freebsd", sdkVariant: "freebsd", targetArchitecture: arch, supportedArchitectures: ["x86_64", "aarch64"], disableOnlyActiveArch: false)
+    }
+
     /// A run destination targeting Android generic device, using the public SDK.
     package static var android: Self {
         return .init(platform: "android", sdk: "android", sdkVariant: "android", targetArchitecture: "undefined_arch", supportedArchitectures: ["armv7", "aarch64", "riscv64", "i686", "x86_64"], disableOnlyActiveArch: true)

Diff for: Sources/SWBTestSupport/SkippedTestSupport.swift

@@ -48,6 +48,8 @@ extension KnownSDK {
             return windows
         case .success(.linux):
             return linux
+        case .success(.freebsd):
+            return freebsd
         case .success(.android):
             return android
         case .success(.unknown), .failure:
@@ -68,6 +70,7 @@ extension KnownSDK {
 extension KnownSDK {
     package static let windows: Self = "windows"
     package static let linux: Self = "linux"
+    package static let freebsd: Self = "freebsd"
     package static let android: Self = "android"
     package static let qnx: Self = "qnx"
     package static let wasi: Self = "wasi"

Diff for: Sources/SWBUtil/Architecture.swift

@@ -98,7 +98,13 @@ public struct Architecture: Sendable {
             if uname(&buf) == 0 {
                 return withUnsafeBytes(of: &buf.machine) { buf in
                     let data = Data(buf)
-                    return String(decoding: data[0...(data.lastIndex(where: { $0 != 0 }) ?? 0)], as: UTF8.self)
+                    let value = String(decoding: data[0...(data.lastIndex(where: { $0 != 0 }) ?? 0)], as: UTF8.self)
+                    switch value {
+                    case "amd64":
+                        return "x86_64"
+                    default:
+                        return value
+                    }
                 }
             }
             return nil

Diff for: Sources/SWBUtil/FSProxy.swift

@@ -761,6 +761,9 @@ class LocalFS: FSProxy, @unchecked Sendable {
         #if os(Windows)
         // Implement ADS on Windows? See also https://github.com/swiftlang/swift-foundation/issues/1166
         return []
+        #elseif os(FreeBSD)
+        // FreeBSD blocked on https://github.com/swiftlang/swift/pull/77836
+        return []
         #elseif os(OpenBSD)
         // OpenBSD no longer supports extended attributes
         return []
@@ -801,6 +804,8 @@ class LocalFS: FSProxy, @unchecked Sendable {
     func setExtendedAttribute(_ path: Path, key: String, value: ByteString) throws {
         #if os(Windows)
         // Implement ADS on Windows? See also https://github.com/swiftlang/swift-foundation/issues/1166
+        #elseif os(FreeBSD)
+        // FreeBSD blocked on https://github.com/swiftlang/swift/pull/77836
         #elseif os(OpenBSD)
         // OpenBSD no longer supports extended attributes
         #else
@@ -821,6 +826,9 @@ class LocalFS: FSProxy, @unchecked Sendable {
         #if os(Windows)
         // Implement ADS on Windows? See also https://github.com/swiftlang/swift-foundation/issues/1166
         return nil
+        #elseif os(FreeBSD)
+        // FreeBSD blocked on https://github.com/swiftlang/swift/pull/77836
+        return nil
         #elseif os(OpenBSD)
         // OpenBSD no longer supports extended attributes
         return nil

Diff for: Sources/SWBUtil/Lock.swift

@@ -28,7 +28,7 @@ public final class Lock: @unchecked Sendable {
     let mutex: UnsafeMutablePointer<SRWLOCK> = UnsafeMutablePointer.allocate(capacity: 1)
     #else
     @usableFromInline
-    let mutex: UnsafeMutablePointer<pthread_mutex_t> = UnsafeMutablePointer.allocate(capacity: 1)
+    let mutex: UnsafeMutablePointer<pthread_mutex_t?> = UnsafeMutablePointer.allocate(capacity: 1)
     #endif
 
     public init() {

Diff for: Sources/SWBUtil/ProcessInfo.swift

@@ -97,6 +97,8 @@ extension ProcessInfo {
         return .windows
         #elseif os(Linux)
         return .linux
+        #elseif os(FreeBSD)
+        return .freebsd
         #else
         if try FileManager.default.isReadableFile(atPath: systemVersionPlistURL.filePath.str) {
             switch try systemVersion().productName {
@@ -125,6 +127,7 @@ public enum OperatingSystem: Hashable, Sendable {
     case visionOS(simulator: Bool)
     case windows
     case linux
+    case freebsd
     case android
     case unknown
 
@@ -153,7 +156,7 @@ public enum OperatingSystem: Hashable, Sendable {
             return .macho
         case .windows:
             return .pe
-        case .linux, .android, .unknown:
+        case .linux, .freebsd, .android, .unknown:
             return .elf
         }
     }

Diff for: Tests/SWBUtilTests/MiscTests.swift

@@ -25,7 +25,7 @@ import SWBUtil
             #expect(SWBUtil.userCacheDir().str.hasPrefix("/var/folders"))
         case .android:
             #expect(SWBUtil.userCacheDir().str.hasPrefix("/data/local/tmp"))
-        case .linux, .unknown:
+        case .linux, .freebsd, .unknown:
             #expect(SWBUtil.userCacheDir().str.hasPrefix("/tmp"))
         }
     }