Fix build warnings

Mostly, ensure that we only use `@_implementationOnly` if we build with `RESILIENT_LIBRARIES`.

Also, `strerror` is marked as unsafe and deprecated on Windows. It looks like this is because `strerror` is not thread-safe. Switch to the thread-safe version `strerror_r` instead.

Author: ahoppen

Package.swift

@@ -184,7 +184,8 @@ let package = Package(
 
     .target(
       name: "SwiftLexicalLookup",
-      dependencies: ["SwiftSyntax", "SwiftIfConfig"]
+      dependencies: ["SwiftSyntax", "SwiftIfConfig"],
+      exclude: ["CMakeLists.txt"]
     ),
 
     .testTarget(

Sources/SwiftCompilerPluginMessageHandling/CompilerPluginMessageHandler.swift

@@ -10,11 +10,19 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if compiler(>=6)
+#if compiler(>=6) && RESILIENT_LIBRARIES
 @_implementationOnly private import _SwiftSyntaxCShims
+#elseif compiler(>=6) && !RESILIENT_LIBRARIES
+private import _SwiftSyntaxCShims
+#elseif !compiler(>=6) && RESILIENT_LIBRARIES
+@_implementationOnly import _SwiftSyntaxCShims
+#elseif !compiler(>=6) && !RESILIENT_LIBRARIES
+import _SwiftSyntaxCShims
+#endif
+
+#if compiler(>=6)
 public import SwiftSyntaxMacros
 #else
-@_implementationOnly import _SwiftSyntaxCShims
 import SwiftSyntaxMacros
 #endif
 

Sources/SwiftCompilerPluginMessageHandling/JSON/JSONDecoding.swift

@@ -10,10 +10,14 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if compiler(>=6)
+#if compiler(>=6) && RESILIENT_LIBRARIES
 @_implementationOnly private import _SwiftSyntaxCShims
-#else
+#elseif compiler(>=6) && !RESILIENT_LIBRARIES
+private import _SwiftSyntaxCShims
+#elseif !compiler(>=6) && RESILIENT_LIBRARIES
 @_implementationOnly import _SwiftSyntaxCShims
+#elseif !compiler(>=6) && !RESILIENT_LIBRARIES
+import _SwiftSyntaxCShims
 #endif
 
 func decodeFromJSON<T: Decodable>(json: UnsafeBufferPointer<UInt8>) throws -> T {

Sources/SwiftCompilerPluginMessageHandling/StandardIOMessageConnection.swift

@@ -10,10 +10,14 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if compiler(>=6)
+#if compiler(>=6) && RESILIENT_LIBRARIES
 @_implementationOnly private import _SwiftSyntaxCShims
-#else
+#elseif compiler(>=6) && !RESILIENT_LIBRARIES
+private import _SwiftSyntaxCShims
+#elseif !compiler(>=6) && RESILIENT_LIBRARIES
 @_implementationOnly import _SwiftSyntaxCShims
+#elseif !compiler(>=6) && !RESILIENT_LIBRARIES
+import _SwiftSyntaxCShims
 #endif
 
 #if canImport(ucrt)
@@ -173,6 +177,13 @@ private enum IOError: Error, CustomStringConvertible {
 
 // Private function to construct an error message from an `errno` code.
 private func describe(errno: CInt) -> String {
-  if let cStr = strerror(errno) { return String(cString: cStr) }
-  return String(describing: errno)
+  // We can't tell how long the error message will be but 1024 characters should be enough to hold most, if not all,
+  // error messages.
+  return withUnsafeTemporaryAllocation(of: CChar.self, capacity: 1024) { buffer in
+    guard let baseAddress = buffer.baseAddress else {
+      return ""
+    }
+    strerror_r(errno, baseAddress, buffer.count)
+    return String(cString: baseAddress)
+  }
 }

Sources/SwiftLibraryPluginProvider/LibraryPluginProvider.swift

@@ -10,12 +10,23 @@
 //
 //===----------------------------------------------------------------------===//
 
+// NOTE: Do not use '_SwiftSyntaxCShims' for 'dlopen' and 'LoadLibraryW' (Windows)
+// because we don't want other modules depend on 'WinSDK'.
+#if compiler(>=6) && RESILIENT_LIBRARIES
+@_implementationOnly private import _SwiftSyntaxCShims
+#elseif compiler(>=6) && !RESILIENT_LIBRARIES
+private import _SwiftSyntaxCShims
+#elseif !compiler(>=6) && RESILIENT_LIBRARIES
+@_implementationOnly import _SwiftSyntaxCShims
+#elseif !compiler(>=6) && !RESILIENT_LIBRARIES
+import _SwiftSyntaxCShims
+#endif
+
 #if compiler(>=6)
 public import SwiftSyntaxMacros
 @_spi(PluginMessage) public import SwiftCompilerPluginMessageHandling
 private import _SwiftLibraryPluginProviderCShims
-// NOTE: Do not use '_SwiftSyntaxCShims' for 'dlopen' and 'LoadLibraryW' (Windows)
-// because we don't want other modules depend on 'WinSDK'.
+
 #if canImport(Darwin)
 private import Darwin
 #elseif canImport(Glibc)
@@ -24,19 +35,38 @@ private import Glibc
 private import Musl
 #elseif canImport(Android)
 private import Android
-#endif
-#else
+#endif  // canImport
+
+#else  // compiler(>=6)
+
 import SwiftSyntaxMacros
 @_spi(PluginMessage) import SwiftCompilerPluginMessageHandling
+
+#if RESILIENT_LIBRARIES
+
 @_implementationOnly import _SwiftLibraryPluginProviderCShims
 #if canImport(Darwin)
 @_implementationOnly import Darwin
 #elseif canImport(Glibc)
 @_implementationOnly import Glibc
 #elseif canImport(Musl)
 @_implementationOnly import Musl
-#endif
-#endif
+#endif  // canImport
+
+#else  // RESILIENT_LIBRARIES
+
+import _SwiftLibraryPluginProviderCShims
+#if canImport(Darwin)
+import Darwin
+#elseif canImport(Glibc)
+import Glibc
+#elseif canImport(Musl)
+import Musl
+#endif  // canImport
+
+#endif  // RESILIENT_LIBRARIES
+
+#endif  // compiler(>=6)
 
 /// Singleton 'PluginProvider' that can serve shared library plugins.
 @_spi(PluginMessage)

Sources/SwiftSyntax/Raw/RawSyntaxArena.swift

@@ -10,10 +10,14 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if compiler(>=6)
+#if compiler(>=6) && RESILIENT_LIBRARIES
 @_implementationOnly private import _SwiftSyntaxCShims
-#else
+#elseif compiler(>=6) && !RESILIENT_LIBRARIES
+private import _SwiftSyntaxCShims
+#elseif !compiler(>=6) && RESILIENT_LIBRARIES
 @_implementationOnly import _SwiftSyntaxCShims
+#elseif !compiler(>=6) && !RESILIENT_LIBRARIES
+import _SwiftSyntaxCShims
 #endif
 
 /// A syntax arena owns the memory for all syntax nodes within it.

Sources/SwiftSyntax/Syntax.swift

@@ -10,10 +10,14 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if compiler(>=6)
+#if compiler(>=6) && RESILIENT_LIBRARIES
 @_implementationOnly private import _SwiftSyntaxCShims
-#else
+#elseif compiler(>=6) && !RESILIENT_LIBRARIES
+private import _SwiftSyntaxCShims
+#elseif !compiler(>=6) && RESILIENT_LIBRARIES
 @_implementationOnly import _SwiftSyntaxCShims
+#elseif !compiler(>=6) && !RESILIENT_LIBRARIES
+import _SwiftSyntaxCShims
 #endif
 
 // `Syntax` is a user facing tree wrapping `RawSyntax` tree. A value is a pair