Add support for WASILibc module (#159)

Quoting the [wasi.dev landing page](https://wasi.dev):
> The WebAssembly System Interface (WASI) is a group of standard API specifications for software compiled to the W3C WebAssembly (Wasm) standard. WASI is designed to provide a secure standard interface for applications that can be compiled to Wasm from any language, and that may run anywhere—from browsers to clouds to embedded devices.

Currently support for WASI in Swift is based on [`wasi-libc`](https://github.com/WebAssembly/wasi-libc).

Adding support for `wasi-libc` mostly amounted to excluding unsupported errnos, adding TLS dictionary storage shim for single-threaded environment, and adding constants in C headers for macros that Clang importer currently doesn't support.

Co-authored-by: Guillaume Lessard <[email protected]>

Author: MaxDesiatov

Sources/CSystem/include/CSystemWASI.h

@@ -0,0 +1,31 @@
+/*
+ This source file is part of the Swift System open source project
+
+ Copyright (c) 2024 Apple Inc. and the Swift System project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See https://swift.org/LICENSE.txt for license information
+*/
+
+#pragma once
+
+#if __wasi__
+
+#include <errno.h>
+#include <fcntl.h>
+
+// wasi-libc defines the following constants in a way that Clang Importer can't
+// understand, so we need to expose them manually.
+static inline int32_t _getConst_O_ACCMODE(void) { return O_ACCMODE; }
+static inline int32_t _getConst_O_APPEND(void) { return O_APPEND; }
+static inline int32_t _getConst_O_CREAT(void) { return O_CREAT; }
+static inline int32_t _getConst_O_DIRECTORY(void) { return O_DIRECTORY; }
+static inline int32_t _getConst_O_EXCL(void) { return O_EXCL; }
+static inline int32_t _getConst_O_NONBLOCK(void) { return O_NONBLOCK; }
+static inline int32_t _getConst_O_TRUNC(void) { return O_TRUNC; }
+static inline int32_t _getConst_O_WRONLY(void) { return O_WRONLY; }
+
+static inline int32_t _getConst_EWOULDBLOCK(void) { return EWOULDBLOCK; }
+static inline int32_t _getConst_EOPNOTSUPP(void) { return EOPNOTSUPP; }
+
+#endif

Sources/CSystem/include/module.modulemap

@@ -1,5 +1,6 @@
 module CSystem {
   header "CSystemLinux.h"
+  header "CSystemWASI.h"
   header "CSystemWindows.h"
   export *
 }

Sources/System/Errno.swift

@@ -1,7 +1,7 @@
 /*
  This source file is part of the Swift System open source project
 
- Copyright (c) 2020 Apple Inc. and the Swift System project authors
+ Copyright (c) 2021 - 2024 Apple Inc. and the Swift System project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See https://swift.org/LICENSE.txt for license information
@@ -229,7 +229,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @available(*, unavailable, renamed: "badAddress")
   public static var EFAULT: Errno { badAddress }
 
-#if !os(Windows)
+#if !os(Windows) && !os(WASI)
   /// Not a block device.
   ///
   /// You attempted a block device operation on a nonblock device or file.
@@ -621,6 +621,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @available(*, unavailable, renamed: "protocolNotSupported")
   public static var EPROTONOSUPPORT: Errno { protocolNotSupported }
 
+#if !os(WASI)
   /// Socket type not supported.
   ///
   /// Support for the socket type hasn't been configured into the system
@@ -633,6 +634,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @_alwaysEmitIntoClient
   @available(*, unavailable, renamed: "socketTypeNotSupported")
   public static var ESOCKTNOSUPPORT: Errno { socketTypeNotSupported }
+#endif
 
   /// Not supported.
   ///
@@ -647,6 +649,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @available(*, unavailable, renamed: "notSupported")
   public static var ENOTSUP: Errno { notSupported }
 
+#if !os(WASI)
   /// Protocol family not supported.
   ///
   /// The protocol family hasn't been configured into the system
@@ -659,6 +662,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @_alwaysEmitIntoClient
   @available(*, unavailable, renamed: "protocolFamilyNotSupported")
   public static var EPFNOSUPPORT: Errno { protocolFamilyNotSupported }
+#endif
 
   /// The address family isn't supported by the protocol family.
   ///
@@ -805,6 +809,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @available(*, unavailable, renamed: "socketNotConnected")
   public static var ENOTCONN: Errno { socketNotConnected }
 
+#if !os(WASI)
   /// Can't send after socket shutdown.
   ///
   /// A request to send data wasn't permitted
@@ -818,6 +823,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @_alwaysEmitIntoClient
   @available(*, unavailable, renamed: "socketShutdown")
   public static var ESHUTDOWN: Errno { socketShutdown }
+#endif
 
   /// Operation timed out.
   ///
@@ -874,6 +880,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @available(*, unavailable, renamed: "fileNameTooLong")
   public static var ENAMETOOLONG: Errno { fileNameTooLong }
 
+#if !os(WASI)
   /// The host is down.
   ///
   /// A socket operation failed because the destination host was down.
@@ -885,6 +892,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @_alwaysEmitIntoClient
   @available(*, unavailable, renamed: "hostIsDown")
   public static var EHOSTDOWN: Errno { hostIsDown }
+#endif
 
   /// No route to host.
   ///
@@ -923,6 +931,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   public static var EPROCLIM: Errno { tooManyProcesses }
 #endif
 
+#if !os(WASI)
   /// Too many users.
   ///
   /// The quota system ran out of table entries.
@@ -934,6 +943,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @_alwaysEmitIntoClient
   @available(*, unavailable, renamed: "tooManyUsers")
   public static var EUSERS: Errno { tooManyUsers }
+#endif
 
   /// Disk quota exceeded.
   ///
@@ -1287,6 +1297,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @available(*, unavailable, renamed: "multiHop")
   public static var EMULTIHOP: Errno { multiHop }
 
+#if !os(WASI)
   /// No message available.
   ///
   /// No message was available to be received by the requested operation.
@@ -1298,6 +1309,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @_alwaysEmitIntoClient
   @available(*, unavailable, renamed: "noData")
   public static var ENODATA: Errno { noData }
+#endif
 
   /// Reserved.
   ///
@@ -1311,6 +1323,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @available(*, unavailable, renamed: "noLink")
   public static var ENOLINK: Errno { noLink }
 
+#if !os(WASI)
   /// Reserved.
   ///
   /// This error is reserved for future use.
@@ -1334,6 +1347,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @_alwaysEmitIntoClient
   @available(*, unavailable, renamed: "notStream")
   public static var ENOSTR: Errno { notStream }
+#endif
 #endif
 
   /// Protocol error.
@@ -1350,7 +1364,7 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
   @available(*, unavailable, renamed: "protocolError")
   public static var EPROTO: Errno { protocolError }
 
-#if !os(OpenBSD)
+#if !os(OpenBSD) && !os(WASI)
   /// Reserved.
   ///
   /// This error is reserved for future use.
@@ -1382,7 +1396,6 @@ public struct Errno: RawRepresentable, Error, Hashable, Codable {
 // Constants defined in header but not man page
 @available(/*System 0.0.1: macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0*/iOS 8, *)
 extension Errno {
-
   /// Operation would block.
   ///
   /// The corresponding C error is `EWOULDBLOCK`.
@@ -1393,6 +1406,7 @@ extension Errno {
   @available(*, unavailable, renamed: "wouldBlock")
   public static var EWOULDBLOCK: Errno { wouldBlock }
 
+#if !os(WASI)
   /// Too many references: can't splice.
   ///
   /// The corresponding C error is `ETOOMANYREFS`.
@@ -1412,6 +1426,7 @@ extension Errno {
   @_alwaysEmitIntoClient
   @available(*, unavailable, renamed: "tooManyRemoteLevels")
   public static var EREMOTE: Errno { tooManyRemoteLevels }
+#endif
 
 #if SYSTEM_PACKAGE_DARWIN
   /// No such policy registered.

Sources/System/FileOperations.swift

@@ -1,7 +1,7 @@
 /*
  This source file is part of the Swift System open source project
 
- Copyright (c) 2020 Apple Inc. and the Swift System project authors
+ Copyright (c) 2020 - 2024 Apple Inc. and the Swift System project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See https://swift.org/LICENSE.txt for license information
@@ -369,6 +369,7 @@ extension FileDescriptor {
   }
 }
 
+#if !os(WASI)
 @available(/*System 0.0.2: macOS 12.0, iOS 15.0, watchOS 8.0, tvOS 15.0*/iOS 8, *)
 extension FileDescriptor {
   /// Duplicates this file descriptor and return the newly created copy.
@@ -433,8 +434,9 @@ extension FileDescriptor {
     fatalError("Not implemented")
   }
 }
+#endif
 
-#if !os(Windows)
+#if !os(Windows) && !os(WASI)
 @available(/*System 1.1.0: macOS 12.3, iOS 15.4, watchOS 8.5, tvOS 15.4*/iOS 8, *)
 extension FileDescriptor {
   /// Creates a unidirectional data channel, which can be used for interprocess communication.

Sources/System/Internals/CInterop.swift

@@ -1,7 +1,7 @@
 /*
  This source file is part of the Swift System open source project
 
- Copyright (c) 2020 - 2021 Apple Inc. and the Swift System project authors
+ Copyright (c) 2020 - 2024 Apple Inc. and the Swift System project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See https://swift.org/LICENSE.txt for license information
@@ -18,6 +18,8 @@ import Glibc
 #elseif canImport(Musl)
 @_implementationOnly import CSystem
 import Musl
+#elseif canImport(WASILibc)
+import WASILibc
 #else
 #error("Unsupported Platform")
 #endif