Fix errors when building WasmKit for WASI (#206)

Wasm is the only unsupported platform for WasmKit in [the Swift Package Index build matrix](https://swiftpackageindex.com/swiftwasm/WasmKit).

One possible use case is using features like WAT assembler or component model tools in the browser.

Another use case could be polyfilling a future Wasm feature running with older Wasm features, when running WasmKit itself in an older Wasm engine.

For proper testing we also need to fix `swift test` in the Swift toolchain.

Author: MaxDesiatov

.github/workflows/main.yml

@@ -126,7 +126,7 @@ jobs:
             wasi-swift-sdk-checksum: "b64dfad9e1c9ccdf06f35cf9b1a00317e000df0c0de0b3eb9f49d6db0fcba4d9"
             test-args: "-Xswiftc -DWASMKIT_CI_TOOLCHAIN_NIGHTLY"
 
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-24.04
     name: "build-linux (${{ matrix.swift }})"
 
     steps:
@@ -240,7 +240,7 @@ jobs:
         run: swift test
 
   build-cmake:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-24.04
     container:
       image: swift:6.2-noble
     steps:
@@ -254,3 +254,17 @@ jobs:
       - run: cmake -G Ninja -B ./build
       - run: cmake --build ./build
       - run: ./build/bin/wasmkit-cli --version
+
+  build-wasi:
+    runs-on: ubuntu-24.04
+    container:
+      image: swift:6.2-noble
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install jq
+        run: apt-get update && apt-get install -y jq
+      - name: Install Swift SDK
+        run: swift sdk install https://download.swift.org/swift-6.2-release/wasm/swift-6.2-RELEASE/swift-6.2-RELEASE_wasm.artifactbundle.tar.gz --checksum fe4e8648309fce86ea522e9e0d1dc48e82df6ba6e5743dbf0c53db8429fb5224
+      - name: Build with the Swift SDK
+        run: swift build --swift-sdk "$(swiftc -print-target-info | jq -r '.swiftCompilerTag')_wasm"
+    

Package.swift

@@ -89,14 +89,17 @@ let package = Package(
         .target(
             name: "SystemExtras",
             dependencies: [
-                .product(name: "SystemPackage", package: "swift-system")
+                .product(name: "SystemPackage", package: "swift-system"),
+                .target(name: "CSystemExtras", condition: .when(platforms: [.wasi])),
             ],
             exclude: ["CMakeLists.txt"],
             swiftSettings: [
                 .define("SYSTEM_PACKAGE_DARWIN", .when(platforms: DarwinPlatforms))
             ]
         ),
 
+        .target(name: "CSystemExtras"),
+
         .executableTarget(
             name: "WITTool",
             dependencies: [
@@ -120,8 +123,8 @@ 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-argument-parser", from: "1.5.1"),
+        .package(url: "https://github.com/apple/swift-system", from: "1.5.0"),
     ]
 } else {
     package.dependencies += [

Sources/CLI/Commands/Run.swift

@@ -59,12 +59,16 @@ struct Run: ParsableCommand {
     var directories: [String] = []
 
     enum ThreadingModel: String, ExpressibleByArgument, CaseIterable {
-        case direct
+        #if !os(WASI)
+            case direct
+        #endif
         case token
 
         func resolve() -> EngineConfiguration.ThreadingModel {
             switch self {
-            case .direct: return .direct
+            #if !os(WASI)
+                case .direct: return .direct
+            #endif
             case .token: return .token
             }
         }

Sources/CSystemExtras/CSystemExtras.c

@@ -0,0 +1,5 @@
+#include <time.h>
+
+inline static clockid_t csystemextras_monotonic_clockid() {
+  return CLOCK_MONOTONIC;
+}

Sources/CSystemExtras/include/clock.h

@@ -12,6 +12,9 @@ import Android
 #elseif os(Windows)
 import CSystem
 import ucrt
+#elseif os(WASI)
+import CSystemExtras
+import WASILibc
 #else
 #error("Unsupported Platform")
 #endif
@@ -41,12 +44,17 @@ 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(WASI)
+  @_alwaysEmitIntoClient
+  public static var monotonic: Clock { Clock(rawValue: csystemextras_monotonic_clockid()) }
+  #endif
+
+  #if os(OpenBSD) || os(FreeBSD)
   @_alwaysEmitIntoClient
   public static var uptime: Clock { Clock(rawValue: _CLOCK_UPTIME) }
   #endif
@@ -92,10 +100,10 @@ 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 +112,25 @@ 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 {
+#if os(WASI)
+      return TimeSpec(rawValue: CInterop.TimeSpec(tv_sec: 0, tv_nsec: Int(UTIME_NOW)))
+#else
       return TimeSpec(rawValue: CInterop.TimeSpec(tv_sec: 0, tv_nsec: Int(_UTIME_NOW)))
+#endif
     }
 
     @_alwaysEmitIntoClient
     public static var omit: TimeSpec {
+#if os(WASI)
+      return TimeSpec(rawValue: CInterop.TimeSpec(tv_sec: 0, tv_nsec: Int(UTIME_OMIT)))
+#else
       return TimeSpec(rawValue: CInterop.TimeSpec(tv_sec: 0, tv_nsec: Int(_UTIME_OMIT)))
+#endif
     }
   }
 }

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
@@ -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

Sources/SystemExtras/Constants.swift

@@ -12,6 +12,8 @@ import Android
 #elseif os(Windows)
 import ucrt
 import WinSDK
+#elseif os(WASI)
+import WASILibc
 #else
 #error("Unsupported Platform")
 #endif

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
@@ -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
 

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
@@ -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")