Fix most of the errors when building WasmKit for WASI

MaxDesiatov · MaxDesiatov · commit 72eade3143d1 · 2025-10-10T15:20:19.000+01:00
Wasm is the only unsupported platform for WasmKit in the Swift Package Index build matrix.

One possible use case is when an implementation for a future Wasm feature is emulated with older Wasm features, when running WasmKit itself in an older Wasm engine.

The only remaining roadblock is the lack of `swiftasynccall`, which prevents `_CWasmKit` module from building, but the rest of the modules seem to build fine. For proper testing we also need to fix `swift test` in the Swift toolchain.
diff --git a/Package.swift b/Package.swift
@@ -121,7 +121,7 @@ let package = Package(
 if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
     package.dependencies += [
         .package(url: "https://github.com/apple/swift-argument-parser", from: "1.2.2"),
-        .package(url: "https://github.com/apple/swift-system", .upToNextMajor(from: "1.3.0")),
+        .package(url: "https://github.com/apple/swift-system", from: "1.6.0"),
     ]
 } else {
     package.dependencies += [
diff --git a/Sources/SystemExtras/Clock.swift b/Sources/SystemExtras/Clock.swift
@@ -12,6 +12,8 @@ import Android
 #elseif os(Windows)
 import CSystem
 import ucrt
+#elseif os(WASI)
+import WASILibc
 #else
 #error("Unsupported Platform")
 #endif
@@ -41,12 +43,12 @@ extension Clock {
   public static var rawMonotonic: Clock { Clock(rawValue: _CLOCK_MONOTONIC_RAW) }
   #endif
 
-  #if SYSTEM_PACKAGE_DARWIN || os(Linux) || os(Android) || os(OpenBSD) || os(FreeBSD) || os(WASI)
+  #if SYSTEM_PACKAGE_DARWIN || os(Linux) || os(Android) || os(OpenBSD) || os(FreeBSD)
   @_alwaysEmitIntoClient
   public static var monotonic: Clock { Clock(rawValue: _CLOCK_MONOTONIC) }
   #endif
 
-  #if os(OpenBSD) || os(FreeBSD) || os(WASI)
+  #if os(OpenBSD) || os(FreeBSD)
   @_alwaysEmitIntoClient
   public static var uptime: Clock { Clock(rawValue: _CLOCK_UPTIME) }
   #endif
@@ -92,10 +94,10 @@ extension Clock {
     public var rawValue: CInterop.TimeSpec
 
     @_alwaysEmitIntoClient
-    public var seconds: Int { rawValue.tv_sec }
+    public var seconds: Int64 { .init(rawValue.tv_sec) }
 
     @_alwaysEmitIntoClient
-    public var nanoseconds: Int { rawValue.tv_nsec }
+    public var nanoseconds: Int64 { .init(rawValue.tv_nsec) }
 
     @_alwaysEmitIntoClient
     public init(rawValue: CInterop.TimeSpec) {
@@ -104,17 +106,17 @@ extension Clock {
 
     @_alwaysEmitIntoClient
     public init(seconds: Int, nanoseconds: Int) {
-      self.init(rawValue: CInterop.TimeSpec(tv_sec: seconds, tv_nsec: nanoseconds))
+      self.init(rawValue: CInterop.TimeSpec(tv_sec: .init(seconds), tv_nsec: nanoseconds))
     }
 
     @_alwaysEmitIntoClient
     public static var now: TimeSpec {
-      return TimeSpec(rawValue: CInterop.TimeSpec(tv_sec: 0, tv_nsec: Int(_UTIME_NOW)))
+      return TimeSpec(rawValue: CInterop.TimeSpec(tv_sec: 0, tv_nsec: Int(UTIME_NOW)))
     }
 
     @_alwaysEmitIntoClient
     public static var omit: TimeSpec {
-      return TimeSpec(rawValue: CInterop.TimeSpec(tv_sec: 0, tv_nsec: Int(_UTIME_OMIT)))
+      return TimeSpec(rawValue: CInterop.TimeSpec(tv_sec: 0, tv_nsec: Int(UTIME_OMIT)))
     }
   }
 }
diff --git a/Sources/SystemExtras/Constants.swift b/Sources/SystemExtras/Constants.swift
@@ -12,6 +12,8 @@ import Android
 #elseif os(Windows)
 import CSystem
 import ucrt
+#elseif os(WASI)
+import WASILibc
 #else
 #error("Unsupported Platform")
 #endif
@@ -43,7 +45,7 @@ internal var _AT_NO_AUTOMOUNT: CInt { AT_NO_AUTOMOUNT }
 #endif
 */
 
-#if !os(Windows)
+#if !os(Windows) && !os(WASI)
 @_alwaysEmitIntoClient
 internal var _F_GETFL: CInt { F_GETFL }
 @_alwaysEmitIntoClient
@@ -61,7 +63,7 @@ internal var _O_SYNC: CInt { O_SYNC }
 internal var _O_RSYNC: CInt { O_RSYNC }
 #endif
 
-#if !os(Windows)
+#if !os(Windows) && !os(WASI)
 @_alwaysEmitIntoClient
 internal var _UTIME_NOW: CInt {
     #if os(Linux) || os(Android)
@@ -132,16 +134,15 @@ internal var _CLOCK_BOOTTIME: CInterop.ClockId { CLOCK_BOOTTIME }
 @_alwaysEmitIntoClient
 internal var _CLOCK_MONOTONIC_RAW: CInterop.ClockId { CLOCK_MONOTONIC_RAW }
 #endif
-#if SYSTEM_PACKAGE_DARWIN || os(Linux) || os(Android) || os(OpenBSD) || os(FreeBSD) || os(WASI)
+#if SYSTEM_PACKAGE_DARWIN || os(Linux) || os(Android) || os(OpenBSD) || os(FreeBSD)
 @_alwaysEmitIntoClient
 internal var _CLOCK_MONOTONIC: CInterop.ClockId { CLOCK_MONOTONIC }
 #endif
-
 #if SYSTEM_PACKAGE_DARWIN
 @_alwaysEmitIntoClient
 internal var _CLOCK_UPTIME_RAW: CInterop.ClockId { CLOCK_UPTIME_RAW }
 #endif
-#if os(OpenBSD) || os(FreeBSD) || os(WASI)
+#if os(OpenBSD) || os(FreeBSD)
 @_alwaysEmitIntoClient
 internal var _CLOCK_UPTIME: CInterop.ClockId { CLOCK_UPTIME }
 #endif
diff --git a/Sources/SystemExtras/FileAtOperations.swift b/Sources/SystemExtras/FileAtOperations.swift
@@ -12,6 +12,8 @@ import Android
 #elseif os(Windows)
 import ucrt
 import WinSDK
+#elseif os(WASI)
+import WASILibc
 #else
 #error("Unsupported Platform")
 #endif
diff --git a/Sources/SystemExtras/FileOperations.swift b/Sources/SystemExtras/FileOperations.swift
@@ -12,6 +12,8 @@ import Android
 #elseif os(Windows)
 import ucrt
 import WinSDK
+#elseif os(WASI)
+import WASILibc
 #else
 #error("Unsupported Platform")
 #endif
@@ -344,6 +346,8 @@ extension FileDescriptor {
     #if os(Windows)
     // FIXME: Need to query by `NtQueryInformationFile`?
     return .success(OpenOptions(rawValue: 0))
+    #elseif os(WASI)
+    return .failure(Errno.notSupported)
     #else
     valueOrErrno(retryOnInterrupt: false) {
       system_fcntl(self.rawValue, _F_GETFL)
@@ -511,15 +515,31 @@ extension FileDescriptor {
 
     @_alwaysEmitIntoClient
     public var name: String {
+#if os(WASI)
+      // ClangImporter can't handle `char d_name[]`, but it's right after `unsigned char d_type`.
+      withUnsafePointer(to: &rawValue.pointee.d_type) { dType in
+        let dName = dType + 1
+        return dName.withMemoryRebound(to: UInt8.self, capacity: MemoryLayout.size(ofValue: dName)) {
+          // String initializer copies the given buffer contents, so it's safe.
+          return String(cString: $0)
+        }
+      }
+#else
       withUnsafePointer(to: &rawValue.pointee.d_name) { dName in
         dName.withMemoryRebound(to: UInt8.self, capacity: MemoryLayout.size(ofValue: dName)) {
           // String initializer copies the given buffer contents, so it's safe.
           return String(cString: $0)
         }
       }
+      #endif
     }
 
     public var fileType: FileType {
+#if os(WASI)
+      // https://github.com/WebAssembly/WASI/blob/main/legacy/preview1/docs.md#-filetype-variant
+      // https://github.com/WebAssembly/wasi-libc/blob/6b45da5b05bc0edda355a6de46101d4b21631985/libc-bottom-half/headers/public/wasi/api.h#L780C9-L780C32
+      FileType(rawValue: .init(rawValue.pointee.d_type))
+#else
       switch CInt(rawValue.pointee.d_type) {
       case _DT_REG: return .file
       case _DT_BLK: return .blockDevice
@@ -529,6 +549,7 @@ extension FileDescriptor {
       case _DT_SOCK: return .socket
       default: return .unknown
       }
+#endif
     }
   }
 
@@ -657,7 +678,7 @@ public enum FileTime {
 public typealias FileTime = Clock.TimeSpec
 #endif
 
-#if !os(Windows)
+#if !os(Windows) && !os(WASI)
 
 // MARK: - Synchronized Input and Output
 
diff --git a/Sources/SystemExtras/Syscalls.swift b/Sources/SystemExtras/Syscalls.swift
@@ -12,6 +12,8 @@ import Android
 #elseif os(Windows)
 import ucrt
 import WinSDK
+#elseif os(WASI)
+import WASILibc
 #else
 #error("Unsupported Platform")
 #endif
@@ -127,7 +129,7 @@ internal func system_symlinkat(
 extension CInterop {
   #if SYSTEM_PACKAGE_DARWIN
   public typealias DirP = UnsafeMutablePointer<DIR>
-  #elseif os(Linux) || os(Android)
+  #elseif os(Linux) || os(Android) || os(WASI)
   public typealias DirP = OpaquePointer
   #else
   #error("Unsupported Platform")
diff --git a/Sources/WASI/Platform/PlatformTypes.swift b/Sources/WASI/Platform/PlatformTypes.swift
@@ -40,15 +40,17 @@ extension WASIAbi.Fdflags {
             if platformOpenOptions.contains(.append) {
                 fdFlags.insert(.APPEND)
             }
-            if platformOpenOptions.contains(.dataSync) {
-                fdFlags.insert(.DSYNC)
-            }
             if platformOpenOptions.contains(.nonBlocking) {
                 fdFlags.insert(.NONBLOCK)
             }
+#if !os(WASI)
+            if platformOpenOptions.contains(.dataSync) {
+                fdFlags.insert(.DSYNC)
+            }
             if platformOpenOptions.contains(.fileSync) {
                 fdFlags.insert(.SYNC)
             }
+#endif
             #if os(Linux)
                 if platformOpenOptions.contains(.readSync) {
                     fdFlags.insert(.RSYNC)
@@ -64,15 +66,17 @@ extension WASIAbi.Fdflags {
             flags.insert(.append)
         }
         #if !os(Windows)
-            if self.contains(.DSYNC) {
-                flags.insert(.dataSync)
-            }
             if self.contains(.NONBLOCK) {
                 flags.insert(.nonBlocking)
             }
+#if !os(WASI)
+            if self.contains(.DSYNC) {
+                flags.insert(.dataSync)
+            }
             if self.contains(.SYNC) {
                 flags.insert(.fileSync)
             }
+#endif
             #if os(Linux)
                 if self.contains(.RSYNC) {
                     flags.insert(.readSync)
diff --git a/Sources/WASI/Platform/SandboxPrimitives/Open.swift b/Sources/WASI/Platform/SandboxPrimitives/Open.swift
@@ -15,6 +15,8 @@ import SystemPackage
 #elseif os(Windows)
     import CSystem
     import ucrt
+#elseif os(WASI)
+    import WASILibc
 #else
     #error("Unsupported Platform")
 #endif
diff --git a/Sources/WASI/WASI.swift b/Sources/WASI/WASI.swift
@@ -12,6 +12,8 @@ import WasmTypes
     import Android
 #elseif os(Windows)
     import ucrt
+#elseif os(WASI)
+    import WASILibc
 #else
     #error("Unsupported Platform")
 #endif
@@ -1391,7 +1393,7 @@ public class WASIBridgeToHost: WASI {
         fdTable[2] = .file(StdioFileEntry(fd: stderr, accessMode: .write))
 
         for (guestPath, hostPath) in preopens {
-            #if os(Windows)
+            #if os(Windows) || os(WASI)
                 let fd = try FileDescriptor.open(FilePath(hostPath), .readWrite)
             #else
                 let fd = try hostPath.withCString { cHostPath in
diff --git a/Sources/WIT/PackageResolver.swift b/Sources/WIT/PackageResolver.swift
@@ -195,52 +195,50 @@ extension SourceFileSyntax {
     }
 }
 
-#if !os(WASI)
-    /// A ``PackageFileLoader`` adapter for local file system.
-    public struct LocalFileLoader: PackageFileLoader {
-        public typealias FilePath = String
+/// A ``PackageFileLoader`` adapter for local file system.
+public struct LocalFileLoader: PackageFileLoader {
+    public typealias FilePath = String
 
-        let fileManager: FileManager
+    let fileManager: FileManager
 
-        public init(fileManager: FileManager = .default) {
-            self.fileManager = fileManager
-        }
+    public init(fileManager: FileManager = .default) {
+        self.fileManager = fileManager
+    }
 
-        enum Error: Swift.Error {
-            case failedToLoadFile(FilePath)
-        }
+    enum Error: Swift.Error {
+        case failedToLoadFile(FilePath)
+    }
 
-        private func isDirectory(filePath: String) -> Bool {
-            var isDirectory: ObjCBool = false
-            let exists = fileManager.fileExists(atPath: filePath, isDirectory: &isDirectory)
-            return exists && isDirectory.boolValue
-        }
+    private func isDirectory(filePath: String) -> Bool {
+        var isDirectory: ObjCBool = false
+        let exists = fileManager.fileExists(atPath: filePath, isDirectory: &isDirectory)
+        return exists && isDirectory.boolValue
+    }
 
-        public func contentsOfWITFile(at filePath: String) throws -> String {
-            guard let bytes = fileManager.contents(atPath: filePath) else {
-                throw Error.failedToLoadFile(filePath)
-            }
-            return String(decoding: bytes, as: UTF8.self)
+    public func contentsOfWITFile(at filePath: String) throws -> String {
+        guard let bytes = fileManager.contents(atPath: filePath) else {
+            throw Error.failedToLoadFile(filePath)
         }
+        return String(decoding: bytes, as: UTF8.self)
+    }
 
-        public func packageFiles(in packageDirectory: String) throws -> [String] {
-            let dirURL = URL(fileURLWithPath: packageDirectory)
-            return try fileManager.contentsOfDirectory(atPath: packageDirectory).filter { fileName in
-                return fileName.hasSuffix(".wit")
-                    && {
-                        let filePath = dirURL.appendingPathComponent(fileName)
-                        return !isDirectory(filePath: filePath.path)
-                    }()
-            }
-            .map { dirURL.appendingPathComponent($0).path }
+    public func packageFiles(in packageDirectory: String) throws -> [String] {
+        let dirURL = URL(fileURLWithPath: packageDirectory)
+        return try fileManager.contentsOfDirectory(atPath: packageDirectory).filter { fileName in
+            return fileName.hasSuffix(".wit")
+                && {
+                    let filePath = dirURL.appendingPathComponent(fileName)
+                    return !isDirectory(filePath: filePath.path)
+                }()
         }
+        .map { dirURL.appendingPathComponent($0).path }
+    }
 
-        public func dependencyDirectories(from packageDirectory: String) throws -> [String] {
-            let dirURL = URL(fileURLWithPath: packageDirectory)
-            let depsDir = dirURL.appendingPathComponent("deps")
-            guard isDirectory(filePath: depsDir.path) else { return [] }
-            return try fileManager.contentsOfDirectory(atPath: depsDir.path)
-        }
+    public func dependencyDirectories(from packageDirectory: String) throws -> [String] {
+        let dirURL = URL(fileURLWithPath: packageDirectory)
+        let depsDir = dirURL.appendingPathComponent("deps")
+        guard isDirectory(filePath: depsDir.path) else { return [] }
+        return try fileManager.contentsOfDirectory(atPath: depsDir.path)
     }
+}
 
-#endif
diff --git a/Sources/WITExtractor/SwiftAPIDigester.swift b/Sources/WITExtractor/SwiftAPIDigester.swift
@@ -118,7 +118,7 @@ struct SwiftAPIDigester {
 
     @available(macOS 11, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
     func dumpSDK(moduleName: String, arguments: [String]) throws -> Output {
-        #if os(iOS) || os(watchOS) || os(tvOS) || os(visionOS)
+        #if os(iOS) || os(watchOS) || os(tvOS) || os(visionOS) || os(WASI)
             fatalError("WITExtractor does not support platforms where Foundation.Process is unavailable")
         #else
             var args = [

Original file line number	Diff line number	Diff line change
`@@ -121,7 +121,7 @@ let package = Package(`
`121`	`121`	`if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {`
`122`	`122`	`package.dependencies += [`
`123`	`123`	`.package(url: "https://github.com/apple/swift-argument-parser", from: "1.2.2"),`
`124`		`- .package(url: "https://github.com/apple/swift-system", .upToNextMajor(from: "1.3.0")),`
	`124`	`+ .package(url: "https://github.com/apple/swift-system", from: "1.6.0"),`
`125`	`125`	`]`
`126`	`126`	`} else {`
`127`	`127`	`package.dependencies += [`