Merge pull request #1091 from apple/revert-1068-revert-1066-revert-392944016fcfc16ea07fe8658c2c5d23cffa6433

Revert "Revert "Revert "Eliminate SWIFT_SYNTAX_ALWAYS_SINGLE_THREADED"""

Author: shahmishal

CMakeLists.txt

@@ -42,6 +42,12 @@ if (NOT SWIFT_SUPPORTS_DISABLE_IMPLICIT_STRING_PROCESSING_MODULE_IMPORT)
     $<$<COMPILE_LANGUAGE:Swift>:-disable-implicit-string-processing-module-import>)
 endif()
 
+# Force single-threaded-only syntax trees to eliminate the Darwin
+# dependency in the compiler.
+add_compile_definitions(
+  $<$<COMPILE_LANGUAGE:Swift>:SWIFT_SYNTAX_ALWAYS_SINGLE_THREADED>
+)
+
 add_subdirectory(Sources)
 
 export(EXPORT SwiftSyntaxTargets

Sources/SwiftSyntax/SyntaxText.swift

@@ -10,6 +10,14 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if !SWIFT_SYNTAX_ALWAYS_SINGLE_THREADED
+#if canImport(Darwin)
+@_implementationOnly import Darwin
+#elseif canImport(Glibc)
+@_implementationOnly import Glibc
+#endif
+#endif
+
 /// Represent a string.
 ///
 /// This type does not own the string data. The data reside in some other buffer
@@ -212,17 +220,17 @@ extension String {
   }
 }
 
-#if os(macOS) || os(iOS) || os(tvOS) || os(watchOS) || os(Linux) || os(FreeBSD) || os(OpenBSD)
-@_silgen_name("memcmp")
-public func memcmp(_: UnsafeRawPointer?, _: UnsafeRawPointer?, _: Int) -> Int32
-#endif
-
 private func compareMemory(
   _ s1: UnsafePointer<UInt8>, _ s2: UnsafePointer<UInt8>, _ count: Int
 ) -> Bool {
   assert(count >= 0)
-#if os(macOS) || os(iOS) || os(tvOS) || os(watchOS) || os(Linux) || os(FreeBSD) || os(OpenBSD)
-  return memcmp(s1, s2, count) == 0
+#if SWIFT_SYNTAX_ALWAYS_SINGLE_THREADED
+  return UnsafeBufferPointer(start: s1, count: count)
+    .elementsEqual(UnsafeBufferPointer(start: s2, count: count))
+#elseif canImport(Darwin)
+  return Darwin.memcmp(s1, s2, count) == 0
+#elseif canImport(Glibc)
+  return Glibc.memcmp(s1, s2, count) == 0
 #else
   return UnsafeBufferPointer(start: s1, count: count)
     .elementsEqual(UnsafeBufferPointer(start: s2, count: count))

Tests/SwiftParserTest/LinkageTests.swift

@@ -32,6 +32,7 @@ final class LinkageTest: XCTestCase {
       .library("-lswiftCompatibility56", condition: .mayBeAbsent("Starting in Xcode 14 this library is not always autolinked")),
       .library("-lswiftCompatibilityConcurrency"),
       .library("-lswiftCore"),
+      .library("-lswiftDarwin", condition: .mayBeAbsent("Not present when building inside the compiler")),
       .library("-lswiftSwiftOnoneSupport", condition: .when(configuration: .debug)),
       .library("-lswift_Concurrency"),
       .library("-lswift_StringProcessing", condition: .mayBeAbsent("Starting in Xcode 14 this library is not always autolinked")),