[tibs] Add -sdk to swift compiles on macOS

When compiling with toolchains that do not include the swift stdlib
(e.g. the Xcode toolchain), we need the SDK path to be explicitly passed
as an argument.

Author: benlangmuir

Sources/ISDBTibs/TibsBuilder.swift

@@ -68,7 +68,8 @@ public final class TibsBuilder {
           emitHeaderPath: clangSources.isEmpty ? nil : "\(name)-Swift.h",
           outputFileMap: outputFileMap,
           bridgingHeader: bridgingHeader,
-          moduleDeps: targetDesc.dependencies?.map { "\($0).swiftmodule" } ?? [])
+          moduleDeps: targetDesc.dependencies?.map { "\($0).swiftmodule" } ?? [],
+          sdk: TibsBuilder.defaultSDKPath)
       }
 
       var clangTUs: [TibsResolvedTarget.ClangTU] = []
@@ -189,6 +190,7 @@ extension TibsBuilder {
           "-emit-objc-header-path", $0
           ] } ?? []
         args += module.bridgingHeader.map { ["-import-objc-header", $0.path] } ?? []
+        args += module.sdk.map { ["-sdk", $0] } ?? []
         args += module.extraArgs
 
         // FIXME: handle via 'directory' field?
@@ -285,7 +287,7 @@ extension TibsBuilder {
           -output-file-map $OUTPUT_FILE_MAP \
           -emit-module -emit-module-path $MODULE_PATH -emit-dependencies \
           -pch-output-dir pch -module-cache-path ModuleCache \
-          $EMIT_HEADER $BRIDGING_HEADER $EXTRA_ARGS \
+          $EMIT_HEADER $BRIDGING_HEADER $SDK $EXTRA_ARGS \
           && \(toolchain.tibs.path) swift-deps-merge $out $DEP_FILES > $out.d
         depfile = $out.d
         deps = gcc
@@ -336,6 +338,7 @@ extension TibsBuilder {
         EXTRA_ARGS = \(module.extraArgs.joined(separator: " "))
         DEP_FILES = \(module.outputFileMap.values.compactMap { $0.dependencies }.joined(separator: " "))
         OUTPUT_FILE_MAP = \(module.outputFileMapPath)
+        SDK = \(module.sdk.map { "-sdk \($0)" } ?? "")
       """)
   }
 
@@ -350,3 +353,40 @@ extension TibsBuilder {
       """)
   }
 }
+
+extension TibsBuilder {
+
+  /// The default sdk path to use on Darwin (on other platforms, returns nil).
+  public static var defaultSDKPath: String? = {
+    #if !os(macOS)
+    return nil
+    #else
+    return xcrunSDKPath()
+    #endif
+  }()
+}
+
+func xcrunSDKPath() -> String {
+  let p = Process()
+  p.launchPath = "/usr/bin/xcrun"
+  p.arguments = ["--show-sdk-path"]
+
+  let out = Pipe()
+  p.standardOutput = out
+
+  p.launch()
+  p.waitUntilExit()
+
+  if p.terminationReason != .exit || p.terminationStatus != 0 {
+    fatalError("unexpected non-zero exit \(p.terminationStatus) from xcrun --show-sdkpath")
+  }
+
+  let data = out.fileHandleForReading.readDataToEndOfFile()
+  guard var path = String(data: data, encoding: .utf8) else {
+    fatalError("invalid output \(data) from xcrun --show-sdkpath")
+  }
+  if path.last == "\n" {
+    path = String(path.dropLast())
+  }
+  return path
+}

Sources/ISDBTibs/TibsResolvedTarget.swift

@@ -31,6 +31,7 @@ public final class TibsResolvedTarget {
     public var bridgingHeader: URL?
     public var moduleDeps: [String]
     public var importPaths: [String] { moduleDeps.isEmpty ? [] : ["."] }
+    public var sdk: String?
 
     public init(
       name: String,
@@ -40,7 +41,8 @@ public final class TibsResolvedTarget {
       emitHeaderPath: String? = nil,
       outputFileMap: OutputFileMap,
       bridgingHeader: URL? = nil,
-      moduleDeps: [String] = [])
+      moduleDeps: [String] = [],
+      sdk: String? = nil)
     {
       self.name = name
       self.extraArgs = extraArgs
@@ -50,6 +52,7 @@ public final class TibsResolvedTarget {
       self.outputFileMap = outputFileMap
       self.bridgingHeader = bridgingHeader
       self.moduleDeps = moduleDeps
+      self.sdk = sdk
     }
   }
 

Tests/ISDBTibsTests/TibsCompilationDatabaseTests.swift

@@ -31,6 +31,8 @@ final class TibsCompilationDatabaseTests: XCTestCase {
     let build = URL(fileURLWithPath: "/build", isDirectory: true)
     let builder = try TibsBuilder(manifest: m, sourceRoot: src, buildRoot: build, toolchain: tc)
 
+    let sdkargs = TibsBuilder.defaultSDKPath.map { ["-sdk", $0] } ?? []
+
     let expected = JSONCompilationDatabase(commands: [
       Command(
         directory: "/build",
@@ -43,8 +45,10 @@ final class TibsCompilationDatabaseTests: XCTestCase {
           "-emit-module", "-emit-module-path", "A.swiftmodule",
           "-emit-dependencies",
           "-pch-output-dir", "pch",
-          "-module-cache-path", "ModuleCache",
-          "-working-directory", "/build"]),
+          "-module-cache-path", "ModuleCache"
+        ] + sdkargs + [
+          "-working-directory", "/build"
+        ]),
       Command(
         directory: "/build",
         file: "/src/b.swift",
@@ -57,8 +61,10 @@ final class TibsCompilationDatabaseTests: XCTestCase {
           "-emit-module", "-emit-module-path", "B.swiftmodule",
           "-emit-dependencies",
           "-pch-output-dir", "pch",
-          "-module-cache-path", "ModuleCache",
-          "-working-directory", "/build"]),
+          "-module-cache-path", "ModuleCache"
+        ] + sdkargs + [
+          "-working-directory", "/build"
+        ]),
       Command(
         directory: "/build",
         file: "/src/c.swift",
@@ -70,8 +76,10 @@ final class TibsCompilationDatabaseTests: XCTestCase {
           "-emit-module", "-emit-module-path", "C.swiftmodule",
           "-emit-dependencies",
           "-pch-output-dir", "pch",
-          "-module-cache-path", "ModuleCache",
-          "-working-directory", "/build"]),
+          "-module-cache-path", "ModuleCache"
+        ] + sdkargs + [
+          "-working-directory", "/build"
+        ]),
     ])
 
     XCTAssertEqual(builder.compilationDatabase, expected)
@@ -85,6 +93,8 @@ final class TibsCompilationDatabaseTests: XCTestCase {
     let build = URL(fileURLWithPath: "/build", isDirectory: true)
     let builder = try TibsBuilder(manifest: m, sourceRoot: src, buildRoot: build, toolchain: tc)
 
+    let sdkargs = TibsBuilder.defaultSDKPath.map { ["-sdk", $0] } ?? []
+
     let swiftArgs = [
       "/swiftc", "/src/a.swift", "/src/b.swift",
       "-module-name", "main",
@@ -96,6 +106,7 @@ final class TibsCompilationDatabaseTests: XCTestCase {
       "-module-cache-path", "ModuleCache",
       "-emit-objc-header", "-emit-objc-header-path", "main-Swift.h",
       "-import-objc-header", "/src/bridging-header.h",
+    ] + sdkargs + [
       "-Xcc", "-Wno-objc-root-class",
       "-working-directory", "/build"
     ]

Tests/ISDBTibsTests/TibsResolutionTests.swift

@@ -53,6 +53,11 @@ final class TibsResolutionTests: XCTestCase {
       src.appendingPathComponent("b.swift", isDirectory: false),
       src.appendingPathComponent("rec/c.swift" , isDirectory: false),
     ])
+    #if os(macOS)
+    XCTAssertNotNil(module.sdk)
+    #else
+    XCTAssertNil(module.sdk)
+    #endif
   }
 
   func testResolutionMixedLangTarget() throws {