Add support for Musl libc (#423)

Since Musl is sufficiently different from Glibc (see https://wiki.musl-libc.org/functional-differences-from-glibc.html), it requires a different import, which now should be applied to files that have `import Glibc` in them.

Author: MaxDesiatov

Sources/TSCBasic/WritableByteStream.swift

@@ -66,7 +66,7 @@ public extension WritableByteStream {
 // Public alias to the old name to not introduce API compatibility.
 public typealias OutputByteStream = WritableByteStream
 
-#if os(Android)
+#if os(Android) || canImport(Musl)
 public typealias FILEPointer = OpaquePointer
 #else
 public typealias FILEPointer = UnsafeMutablePointer<FILE>

Sources/TSCLibc/libc.swift

@@ -10,6 +10,8 @@
 
 #if canImport(Glibc)
 @_exported import Glibc
+#elseif canImport(Musl)
+@_exported import Musl
 #elseif os(Windows)
 @_exported import CRT
 @_exported import WinSDK

Sources/TSCUtility/FSWatch.swift

@@ -54,7 +54,7 @@ public class FSWatch {
         self._watcher = NoOpWatcher(paths: paths, latency: latency, delegate: _WatcherDelegate(block: block))
       #elseif os(Windows)
         self._watcher = RDCWatcher(paths: paths, latency: latency, delegate: _WatcherDelegate(block: block))
-      #elseif canImport(Glibc)
+      #elseif canImport(Glibc) || canImport(Musl)
         var ipaths: [AbsolutePath: Inotify.WatchOptions] = [:]
 
         // FIXME: We need to recurse here.
@@ -106,7 +106,7 @@ extension NoOpWatcher: _FileWatcher{}
 #elseif os(Windows)
 extension FSWatch._WatcherDelegate: RDCWatcherDelegate {}
 extension RDCWatcher: _FileWatcher {}
-#elseif canImport(Glibc)
+#elseif canImport(Glibc) || canImport(Musl)
 extension FSWatch._WatcherDelegate: InotifyDelegate {}
 extension Inotify: _FileWatcher{}
 #elseif os(macOS)
@@ -296,7 +296,7 @@ public final class RDCWatcher {
     }
 }
 
-#elseif canImport(Glibc)
+#elseif canImport(Glibc) || canImport(Musl)
 
 /// The delegate for receiving inotify events.
 public protocol InotifyDelegate {
@@ -621,7 +621,7 @@ public final class Inotify {
 // FIXME: <rdar://problem/45794219> Swift should provide shims for FD_ macros
 
 private func FD_ZERO(_ set: inout fd_set) {
-    #if os(Android)
+    #if os(Android) || canImport(Musl)
         #if arch(arm)
             set.fds_bits = (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
@@ -641,7 +641,7 @@ private func FD_ZERO(_ set: inout fd_set) {
 private func FD_SET(_ fd: Int32, _ set: inout fd_set) {
     let intOffset = Int(fd / 16)
     let bitOffset = Int(fd % 16)
-  #if os(Android)
+  #if os(Android) || canImport(Musl)
     var fd_bits = set.fds_bits
     let mask: UInt = 1 << bitOffset
   #else
@@ -685,7 +685,7 @@ private func FD_SET(_ fd: Int32, _ set: inout fd_set) {
 	#endif
         default: break
     }
-  #if os(Android)
+  #if os(Android) || canImport(Musl)
     set.fds_bits = fd_bits
   #else
     set.__fds_bits = fd_bits
@@ -695,7 +695,7 @@ private func FD_SET(_ fd: Int32, _ set: inout fd_set) {
 private func FD_ISSET(_ fd: Int32, _ set: inout fd_set) -> Bool {
     let intOffset = Int(fd / 32)
     let bitOffset = Int(fd % 32)
-  #if os(Android)
+  #if os(Android) || canImport(Musl)
     let fd_bits = set.fds_bits
     let mask: UInt = 1 << bitOffset
   #else

Sources/TSCUtility/IndexStore.swift

@@ -457,7 +457,7 @@ private struct _DLOpenFlags: RawRepresentable, OptionSet {
     public static let deepBind: _DLOpenFlags = _DLOpenFlags(rawValue: 0)
   #else
     public static let first: _DLOpenFlags = _DLOpenFlags(rawValue: 0)
-  #if os(Linux)
+  #if os(Linux) && canImport(Glibc)
     public static let deepBind: _DLOpenFlags = _DLOpenFlags(rawValue: RTLD_DEEPBIND)
   #else
     public static let deepBind: _DLOpenFlags = _DLOpenFlags(rawValue: 0)

Sources/TSCUtility/InterruptHandler.swift

@@ -8,6 +8,8 @@
  See http://swift.org/CONTRIBUTORS.txt for Swift project authors
 */
 
+#if !canImport(Musl)
+
 import TSCLibc
 import TSCBasic
 
@@ -135,3 +137,5 @@ public final class InterruptHandler {
         thread.join()
     }
 }
+
+#endif

Sources/TSCUtility/dlopen.swift

@@ -66,7 +66,7 @@ public struct DLOpenFlags: RawRepresentable, OptionSet {
     public static let deepBind: DLOpenFlags = DLOpenFlags(rawValue: 0)
   #else
     public static let first: DLOpenFlags = DLOpenFlags(rawValue: 0)
-  #if os(Linux)
+  #if os(Linux) && canImport(Glibc)
     public static let deepBind: DLOpenFlags = DLOpenFlags(rawValue: RTLD_DEEPBIND)
   #else
     public static let deepBind: DLOpenFlags = DLOpenFlags(rawValue: 0)