[ASTGen] Enable C++ interop

CMakeLists.txt

@@ -405,9 +405,10 @@ set(SWIFT_STDLIB_MSVC_RUNTIME_LIBRARY
 
 
 if(BRIDGING_MODE STREQUAL "DEFAULT" OR NOT BRIDGING_MODE)
-  if(CMAKE_BUILD_TYPE STREQUAL "Debug" OR "${CMAKE_SYSTEM_NAME}" STREQUAL "Windows")
+  if(CMAKE_BUILD_TYPE STREQUAL "Debug" OR "${CMAKE_SYSTEM_NAME}" STREQUAL "Windows" OR (CMAKE_Swift_COMPILER AND CMAKE_Swift_COMPILER_VERSION VERSION_LESS 5.8))
     # In debug builds, to workaround a problem with LLDB's `po` command (rdar://115770255).
     # On windows to workaround a build problem.
+    # If the host Swift version is less than 5.8, use pure mode to workaround a C++ interop compiler crash.
     set(BRIDGING_MODE "PURE")
   else()
     set(BRIDGING_MODE "INLINE")

cmake/modules/AddPureSwift.cmake

@@ -37,6 +37,11 @@ function(_add_host_swift_compile_options name)
      target_link_options(${name} PRIVATE ${_cov_flags})
   endif()
 
+  if("${BRIDGING_MODE}" STREQUAL "PURE")
+    target_compile_options(${name} PRIVATE
+      "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xcc -DPURE_BRIDGING_MODE>")
+  endif()
+
   # The compat56 library is not available in current toolchains. The stage-0
   # compiler will build fine since the builder compiler is not aware of the 56
   # compat library, but the stage-1 and subsequent stage compilers will fail as

lib/ASTGen/CMakeLists.txt

@@ -38,3 +38,39 @@ add_pure_swift_host_library(swiftASTGen STATIC
     SwiftSyntaxMacroExpansion
     swiftLLVMJSON
 )
+
+set(c_include_paths
+  # LLVM modules and headers.
+  "${LLVM_MAIN_INCLUDE_DIR}"
+  # Generated LLVM headers.
+  "${LLVM_INCLUDE_DIR}"
+  # Clang modules and headers.
+  ${CLANG_INCLUDE_DIRS}
+  # Bridging modules and headers.
+  "${SWIFT_MAIN_INCLUDE_DIR}"
+  # Generated C headers.
+  "${CMAKE_CURRENT_BINARY_DIR}/../../include")
+set(c_include_paths_args)
+foreach(c_include_path ${c_include_paths})
+  list(APPEND c_include_paths_args "SHELL: -Xcc -I -Xcc ${c_include_path}")
+endforeach()
+
+# Prior to 5.9, we have to use the experimental flag for C++ interop.
+if (CMAKE_Swift_COMPILER_VERSION VERSION_LESS 5.9)
+  set(cxx_interop_flag "-enable-experimental-cxx-interop")
+else()
+  set(cxx_interop_flag "-cxx-interoperability-mode=default")
+endif()
+
+set(compile_options
+  ${c_include_paths_args}
+  "SHELL: ${cxx_interop_flag}"
+  "SHELL: -Xcc -std=c++17 -Xcc -DCOMPILED_WITH_SWIFT"
+
+  # Necessary to avoid treating IBOutlet and IBAction as keywords
+  "SHELL:-Xcc -UIBOutlet -Xcc -UIBAction -Xcc -UIBInspectable"
+)
+
+foreach(target swiftASTGen swiftLLVMJSON)
+  target_compile_options(${target} PRIVATE ${compile_options})
+endforeach()

lib/ASTGen/Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version: 5.6
+// swift-tools-version: 5.9
 
 // The CMake build system is the only one that's able to produce a working
 // compiler. This Package.swift makes it easier to build and work with the
@@ -7,19 +7,37 @@
 // the new Swift parser are better implemented/tested within or on top of the
 // swift-syntax package.
 
+// To successfully build, you'll need to create a couple of symlinks to an
+// existing Ninja build:
+//
+// ln -s <project-root>/build/<Ninja-Build>/llvm-<os+arch> <project-root>/build/Default/llvm
+// ln -s <project-root>/build/<Ninja-Build>/swift-<os+arch> <project-root>/build/Default/swift
+//
+// where <project-root> is the parent directory of the swift repository.
+//
+// FIXME: We may want to consider generating Package.swift as a part of the
+// build.
+
 import PackageDescription
 
 let swiftSetttings: [SwiftSetting] = [
+  .interoperabilityMode(.Cxx),
   .unsafeFlags([
-    "-I", "../../include/swift/",
-    "-I", "../../include",
-  ])
+    "-Xcc", "-DCOMPILED_WITH_SWIFT",
+    "-Xcc", "-UIBOutlet", "-Xcc", "-UIBAction", "-Xcc", "-UIBInspectable",
+    "-Xcc", "-I../../include",
+    "-Xcc", "-I../../../llvm-project/llvm/include",
+    "-Xcc", "-I../../../llvm-project/clang/include",
+    "-Xcc", "-I../../../build/Default/swift/include",
+    "-Xcc", "-I../../../build/Default/llvm/include",
+    "-Xcc", "-I../../../build/Default/llvm/tools/clang/include",
+  ]),
 ]
 
 let package = Package(
   name: "swiftSwiftCompiler",
   platforms: [
-    .macOS(.v10_15)
+    .macOS(.v13)
   ],
   products: [
     .library(name: "swiftASTGen", targets: ["swiftASTGen"]),
@@ -53,5 +71,6 @@ let package = Package(
       path: "Sources/LLVMJSON",
       swiftSettings: swiftSetttings
     ),
-  ]
+  ],
+  cxxLanguageStandard: .cxx17
 )

lib/ASTGen/Sources/ASTGen/ASTGen.swift

@@ -380,7 +380,9 @@ extension ASTGenVisitor {
   @inline(__always)
   func generate(_ node: InheritedTypeListSyntax?) -> BridgedArrayRef {
     guard let node else {
-      return .init()
+      // NOTE: You cannot do '.init()' here as that will produce garbage
+      // (rdar://116825963).
+      return .init(data: nil, numElements: 0)
     }
 
     return self.generate(node)
@@ -389,7 +391,9 @@ extension ASTGenVisitor {
   @inline(__always)
   func generate(_ node: PrecedenceGroupNameListSyntax?) -> BridgedArrayRef {
     guard let node else {
-      return .init()
+      // NOTE: You cannot do '.init()' here as that will produce garbage
+      // (rdar://116825963).
+      return .init(data: nil, numElements: 0)
     }
 
     return self.generate(node)
@@ -403,7 +407,9 @@ extension Collection {
   ///   on a ``LazyFilterSequence`` due to the `count` access.
   func compactMap<T>(in astgen: ASTGenVisitor, _ transform: (Element) -> T?) -> BridgedArrayRef {
     if self.isEmpty {
-      return .init()
+      // NOTE: You cannot do '.init()' here as that will produce garbage
+      // (rdar://116825963).
+      return .init(data: nil, numElements: 0)
     }
 
     let baseAddress = astgen.allocator.allocate(T.self, count: self.count).baseAddress!
@@ -429,7 +435,9 @@ extension LazyCollectionProtocol {
   /// Returns a copy of the collection's elements as a `BridgedArrayRef` with a lifetime tied to that of `astgen`.
   func bridgedArray(in astgen: ASTGenVisitor) -> BridgedArrayRef {
     if self.isEmpty {
-      return .init()
+      // NOTE: You cannot do '.init()' here as that will produce garbage
+      // (rdar://116825963).
+      return .init(data: nil, numElements: 0)
     }
 
     let buffer = astgen.allocator.allocate(Element.self, count: self.count)
@@ -455,7 +463,9 @@ extension Optional where Wrapped: LazyCollectionProtocol {
   @inline(__always)
   func bridgedArray(in astgen: ASTGenVisitor) -> BridgedArrayRef {
     guard let self else {
-      return .init()
+      // NOTE: You cannot do '.init()' here as that will produce garbage
+      // (rdar://116825963).
+      return .init(data: nil, numElements: 0)
     }
 
     return self.bridgedArray(in: astgen)

lib/ASTGen/Sources/ASTGen/Macros.swift

@@ -400,7 +400,9 @@ func makeExpansionOutputResult(
   outputPointer: UnsafeMutablePointer<BridgedString>
 ) -> Int {
   guard var expandedSource = expandedSource else {
-    outputPointer.pointee = BridgedString()
+    // NOTE: You cannot use 'init()' here as that will produce garbage
+    // (rdar://116825963).
+    outputPointer.pointee = BridgedString(data: nil, length: 0)
     return -1
   }
   outputPointer.pointee = allocateBridgedString(expandedSource)

lib/ASTGen/Sources/ASTGen/PluginHost.swift

@@ -127,7 +127,9 @@ struct CompilerPlugin {
   }
 
   private func waitForNextMessage() throws -> PluginToHostMessage {
-    var result: BridgedData = BridgedData()
+    // NOTE: You cannot use 'init()' here as that will produce garbage
+    // (rdar://116825963).
+    var result = BridgedData(baseAddress: nil, size: 0)
     let hadError = Plugin_waitForNextMessage(opaqueHandle, &result)
     defer { BridgedData_free(result) }
     guard !hadError else {