Bitcode strip Flutter.framework in assemble build target (#77329)

dev/devicelab/lib/framework/ios.dart

@@ -42,7 +42,7 @@ Future<bool> containsBitcode(String pathToBinary) async {
     if (line.contains('segname __LLVM') && lines.length - index - 1 > 3) {
       final String emptyBitcodeMarker = lines
         .skip(index - 1)
-        .take(3)
+        .take(4)
         .firstWhere(
           (String line) => line.contains(' size 0x0000000000000001'),
           orElse: () => null,

packages/flutter_tools/bin/xcode_backend.sh

@@ -137,9 +137,8 @@ is set to release or run \"flutter build ios --release\", then re-run Archive fr
     local_engine_flag="--local-engine=${LOCAL_ENGINE}"
     flutter_framework="${FLUTTER_ENGINE}/out/${LOCAL_ENGINE}/Flutter.xcframework"
   fi
-
   local bitcode_flag=""
-  if [[ "$ENABLE_BITCODE" == "YES" ]]; then
+  if [[ "$ENABLE_BITCODE" == "YES" && "$ACTION" == "install" ]]; then
     bitcode_flag="true"
   fi
 
@@ -218,10 +217,6 @@ EmbedFlutterFrameworks() {
 
   # Copy Xcode behavior and don't copy over headers or modules.
   RunCommand rsync -av --delete --filter "- .DS_Store" --filter "- Headers" --filter "- Modules" "${BUILT_PRODUCTS_DIR}/Flutter.framework" "${xcode_frameworks_dir}/"
-  if [[ "$ACTION" != "install" || "$ENABLE_BITCODE" == "NO" ]]; then
-    # Strip bitcode from the destination unless archiving, or if bitcode is disabled entirely.
-    RunCommand "${DT_TOOLCHAIN_DIR}"/usr/bin/bitcode_strip "${BUILT_PRODUCTS_DIR}/Flutter.framework/Flutter" -r -o "${xcode_frameworks_dir}/Flutter.framework/Flutter"
-  fi
 
   # Sign the binaries we moved.
   if [[ -n "${EXPANDED_CODE_SIGN_IDENTITY:-}" ]]; then

packages/flutter_tools/lib/src/build_system/targets/ios.dart

@@ -280,8 +280,18 @@ abstract class UnpackIOS extends Target {
     if (environment.defines[kIosArchs] == null) {
       throw MissingDefineException(kIosArchs, name);
     }
+    if (environment.defines[kBitcodeFlag] == null) {
+      throw MissingDefineException(kBitcodeFlag, name);
+    }
     await _copyFramework(environment);
-    await _thinFramework(environment);
+
+    final File frameworkBinary = environment.outputDir.childDirectory('Flutter.framework').childFile('Flutter');
+    final String frameworkBinaryPath = frameworkBinary.path;
+    if (!frameworkBinary.existsSync()) {
+      throw Exception('Binary $frameworkBinaryPath does not exist, cannot thin');
+    }
+    await _thinFramework(environment, frameworkBinaryPath);
+    await _bitcodeStripFramework(environment, frameworkBinaryPath);
   }
 
   Future<void> _copyFramework(Environment environment) async {
@@ -312,37 +322,30 @@ abstract class UnpackIOS extends Target {
   }
 
   /// Destructively thin Flutter.framework to include only the specified architectures.
-  Future<void> _thinFramework(Environment environment) async {
-    final Directory frameworkDirectory = environment.outputDir;
-
-    final File flutterFramework = frameworkDirectory.childDirectory('Flutter.framework').childFile('Flutter');
-    final String binaryPath = flutterFramework.path;
-    if (!flutterFramework.existsSync()) {
-      throw Exception('Binary $binaryPath does not exist, cannot thin');
-    }
+  Future<void> _thinFramework(Environment environment, String frameworkBinaryPath) async {
     final String archs = environment.defines[kIosArchs];
     final List<String> archList = archs.split(' ').toList();
     final ProcessResult infoResult = environment.processManager.runSync(<String>[
       'lipo',
       '-info',
-      binaryPath,
+      frameworkBinaryPath,
     ]);
     final String lipoInfo = infoResult.stdout as String;
 
     final ProcessResult verifyResult = environment.processManager.runSync(<String>[
       'lipo',
-      binaryPath,
+      frameworkBinaryPath,
       '-verify_arch',
       ...archList
     ]);
 
     if (verifyResult.exitCode != 0) {
-      throw Exception('Binary $binaryPath does not contain $archs. Running lipo -info:\n$lipoInfo');
+      throw Exception('Binary $frameworkBinaryPath does not contain $archs. Running lipo -info:\n$lipoInfo');
     }
 
     // Skip thinning for non-fat executables.
     if (lipoInfo.startsWith('Non-fat file:')) {
-      environment.logger.printTrace('Skipping lipo for non-fat file $binaryPath');
+      environment.logger.printTrace('Skipping lipo for non-fat file $frameworkBinaryPath');
       return;
     }
 
@@ -350,17 +353,36 @@ abstract class UnpackIOS extends Target {
     final ProcessResult extractResult = environment.processManager.runSync(<String>[
       'lipo',
       '-output',
-      binaryPath,
+      frameworkBinaryPath,
       for (final String arch in archList)
         ...<String>[
           '-extract',
           arch,
         ],
-      ...<String>[binaryPath],
+      ...<String>[frameworkBinaryPath],
     ]);
 
     if (extractResult.exitCode != 0) {
-      throw Exception('Failed to extract $archs for $binaryPath.\n${extractResult.stderr}\nRunning lipo -info:\n$lipoInfo');
+      throw Exception('Failed to extract $archs for $frameworkBinaryPath.\n${extractResult.stderr}\nRunning lipo -info:\n$lipoInfo');
+    }
+  }
+
+  /// Destructively strip bitcode from the framework, if needed.
+  Future<void> _bitcodeStripFramework(Environment environment, String frameworkBinaryPath) async {
+    if (environment.defines[kBitcodeFlag] == 'true') {
+      return;
+    }
+    final ProcessResult stripResult = environment.processManager.runSync(<String>[
+      'xcrun',
+      'bitcode_strip',
+      frameworkBinaryPath,
+      '-m', // leave the bitcode marker.
+      '-o',
+      frameworkBinaryPath,
+    ]);
+
+    if (stripResult.exitCode != 0) {
+      throw Exception('Failed to strip bitcode for $frameworkBinaryPath.\n${stripResult.stderr}');
     }
   }
 }

packages/flutter_tools/test/general.shard/build_system/targets/ios_test.dart

@@ -239,7 +239,7 @@ void main() {
     Platform: () => macPlatform,
   });
 
-  group('copy and thin engine Flutter.framework', () {
+  group('copy, thin, and bitcode strip engine Flutter.framework', () {
     Directory outputDir;
     FakeCommand copyPhysicalFrameworkCommand;
 
@@ -269,6 +269,7 @@ void main() {
         defines: <String, String>{
           kIosArchs: 'x86_64',
           kSdkRoot: 'path/to/iPhoneSimulator.sdk',
+          kBitcodeFlag: 'true',
         },
       );
 
@@ -308,7 +309,7 @@ void main() {
       expect(processManager.hasRemainingExpectations, isFalse);
     });
 
-    testWithoutContext('thinning fails when frameworks missing', () async {
+    testWithoutContext('fails when frameworks missing', () async {
       final Environment environment = Environment.test(
         fileSystem.currentDirectory,
         processManager: processManager,
@@ -319,10 +320,11 @@ void main() {
         defines: <String, String>{
           kIosArchs: 'arm64',
           kSdkRoot: 'path/to/iPhoneOS.sdk',
+          kBitcodeFlag: '',
         },
       );
       processManager.addCommand(copyPhysicalFrameworkCommand);
-      expect(
+      await expectLater(
         const DebugUnpackIOS().build(environment),
         throwsA(isA<Exception>().having(
           (Exception exception) => exception.toString(),
@@ -331,7 +333,7 @@ void main() {
         )));
     });
 
-    testWithoutContext('thinning fails when requested archs missing from framework', () async {
+    testWithoutContext('fails when requested archs missing from framework', () async {
       final File binary = outputDir.childDirectory('Flutter.framework').childFile('Flutter')..createSync(recursive: true);
 
       final Environment environment = Environment.test(
@@ -344,6 +346,7 @@ void main() {
         defines: <String, String>{
           kIosArchs: 'arm64 armv7',
           kSdkRoot: 'path/to/iPhoneOS.sdk',
+          kBitcodeFlag: '',
         },
       );
 
@@ -366,7 +369,7 @@ void main() {
         ], exitCode: 1),
       );
 
-      expect(
+      await expectLater(
           const DebugUnpackIOS().build(environment),
           throwsA(isA<Exception>().having(
                 (Exception exception) => exception.toString(),
@@ -375,7 +378,7 @@ void main() {
           )));
     });
 
-    testWithoutContext('thinning fails when lipo extract fails', () async {
+    testWithoutContext('fails when lipo extract fails', () async {
       final File binary = outputDir.childDirectory('Flutter.framework').childFile('Flutter')..createSync(recursive: true);
 
       final Environment environment = Environment.test(
@@ -388,6 +391,7 @@ void main() {
         defines: <String, String>{
           kIosArchs: 'arm64 armv7',
           kSdkRoot: 'path/to/iPhoneOS.sdk',
+          kBitcodeFlag: '',
         },
       );
 
@@ -424,7 +428,7 @@ void main() {
         stderr: 'lipo error'),
       );
 
-      expect(
+      await expectLater(
         const DebugUnpackIOS().build(environment),
         throwsA(isA<Exception>().having(
               (Exception exception) => exception.toString(),
@@ -433,7 +437,7 @@ void main() {
         )));
     });
 
-    testWithoutContext('skips thin frameworks', () async {
+    testWithoutContext('skips thin framework', () async {
       final File binary = outputDir.childDirectory('Flutter.framework').childFile('Flutter')..createSync(recursive: true);
 
       final Environment environment = Environment.test(
@@ -446,6 +450,7 @@ void main() {
         defines: <String, String>{
           kIosArchs: 'arm64',
           kSdkRoot: 'path/to/iPhoneOS.sdk',
+          kBitcodeFlag: 'true',
         },
       );
 
@@ -473,7 +478,7 @@ void main() {
       expect(processManager.hasRemainingExpectations, isFalse);
     });
 
-    testWithoutContext('thins fat frameworks', () async {
+    testWithoutContext('thins fat framework', () async {
       final File binary = outputDir.childDirectory('Flutter.framework').childFile('Flutter')..createSync(recursive: true);
 
       final Environment environment = Environment.test(
@@ -486,6 +491,7 @@ void main() {
         defines: <String, String>{
           kIosArchs: 'arm64 armv7',
           kSdkRoot: 'path/to/iPhoneOS.sdk',
+          kBitcodeFlag: 'true',
         },
       );
 
@@ -524,5 +530,100 @@ void main() {
       await const DebugUnpackIOS().build(environment);
       expect(processManager.hasRemainingExpectations, isFalse);
     });
+
+    testWithoutContext('fails when bitcode strip fails', () async {
+      final File binary = outputDir.childDirectory('Flutter.framework').childFile('Flutter')..createSync(recursive: true);
+
+      final Environment environment = Environment.test(
+        fileSystem.currentDirectory,
+        processManager: processManager,
+        artifacts: artifacts,
+        logger: logger,
+        fileSystem: fileSystem,
+        outputDir: outputDir,
+        defines: <String, String>{
+          kIosArchs: 'arm64',
+          kSdkRoot: 'path/to/iPhoneOS.sdk',
+          kBitcodeFlag: '',
+        },
+      );
+
+      processManager.addCommands(<FakeCommand>[
+        copyPhysicalFrameworkCommand,
+        FakeCommand(command: <String>[
+          'lipo',
+          '-info',
+          binary.path,
+        ], stdout: 'Non-fat file:'),
+        FakeCommand(command: <String>[
+          'lipo',
+          binary.path,
+          '-verify_arch',
+          'arm64',
+        ]),
+        FakeCommand(command: <String>[
+          'xcrun',
+          'bitcode_strip',
+          binary.path,
+          '-m',
+          '-o',
+          binary.path,
+        ], exitCode: 1, stderr: 'bitcode_strip error'),
+      ]);
+
+      await expectLater(
+          const DebugUnpackIOS().build(environment),
+          throwsA(isA<Exception>().having(
+                (Exception exception) => exception.toString(),
+            'description',
+            contains('Failed to strip bitcode for output/Flutter.framework/Flutter.\nbitcode_strip error'),
+          )));
+
+      expect(processManager.hasRemainingExpectations, isFalse);
+    });
+
+    testWithoutContext('strips framework', () async {
+      final File binary = outputDir.childDirectory('Flutter.framework').childFile('Flutter')..createSync(recursive: true);
+
+      final Environment environment = Environment.test(
+        fileSystem.currentDirectory,
+        processManager: processManager,
+        artifacts: artifacts,
+        logger: logger,
+        fileSystem: fileSystem,
+        outputDir: outputDir,
+        defines: <String, String>{
+          kIosArchs: 'arm64',
+          kSdkRoot: 'path/to/iPhoneOS.sdk',
+          kBitcodeFlag: '',
+        },
+      );
+
+      processManager.addCommands(<FakeCommand>[
+        copyPhysicalFrameworkCommand,
+        FakeCommand(command: <String>[
+          'lipo',
+          '-info',
+          binary.path,
+        ], stdout: 'Non-fat file:'),
+        FakeCommand(command: <String>[
+          'lipo',
+          binary.path,
+          '-verify_arch',
+          'arm64',
+        ]),
+        FakeCommand(command: <String>[
+          'xcrun',
+          'bitcode_strip',
+          binary.path,
+          '-m',
+          '-o',
+          binary.path,
+        ]),
+      ]);
+      await const DebugUnpackIOS().build(environment);
+
+      expect(processManager.hasRemainingExpectations, isFalse);
+    });
   });
 }

packages/flutter_tools/test/src/darwin_common.dart

@@ -40,7 +40,7 @@ bool containsBitcode(String pathToBinary, ProcessManager processManager) {
   lines.asMap().forEach((int index, String line) {
     if (line.contains('segname __LLVM') && lines.length - index - 1 > 3) {
       final String emptyBitcodeMarker =
-      lines.skip(index - 1).take(3).firstWhere(
+      lines.skip(index - 1).take(4).firstWhere(
             (String line) => line.contains(' size 0x0000000000000001'),
         orElse: () => null,
       );