Stop embedding bitcode for iOS in tool (#112831)

Author: jmagman

dev/devicelab/bin/tasks/build_ios_framework_module_test.dart

@@ -171,7 +171,6 @@ Future<void> _testBuildIosFramework(Directory projectDir, { bool isModule = fals
     );
 
     await _checkDylib(appFrameworkPath);
-    await _checkBitcode(appFrameworkPath, mode);
 
     final String aotSymbols = await _dylibSymbols(appFrameworkPath);
 
@@ -228,15 +227,14 @@ Future<void> _testBuildIosFramework(Directory projectDir, { bool isModule = fals
   section("Check all modes' engine dylib");
 
   for (final String mode in <String>['Debug', 'Profile', 'Release']) {
-    final String engineBinary = path.join(
+    checkFileExists(path.join(
       outputPath,
       mode,
       'Flutter.xcframework',
       'ios-arm64',
       'Flutter.framework',
       'Flutter',
-    );
-    await _checkBitcode(engineBinary, mode);
+    ));
 
     checkFileExists(path.join(
       outputPath,
@@ -836,15 +834,6 @@ Future<void> _checkStatic(String pathToLibrary) async {
   }
 }
 
-Future<void> _checkBitcode(String frameworkPath, String mode) async {
-  checkFileExists(frameworkPath);
-
-  // Bitcode only needed in Release mode for archiving.
-  if (mode == 'Release' && !await containsBitcode(frameworkPath)) {
-    throw TaskResult.failure('$frameworkPath does not contain bitcode');
-  }
-}
-
 Future<String> _dylibSymbols(String pathToDylib) {
   return eval('nm', <String>[
     '-g',

dev/devicelab/lib/framework/ios.dart

@@ -47,43 +47,6 @@ Future<String?> minPhoneOSVersion(String pathToBinary) async {
   return minVersion;
 }
 
-Future<bool> containsBitcode(String pathToBinary) async {
-  // See: https://stackoverflow.com/questions/32755775/how-to-check-a-static-library-is-built-contain-bitcode
-  final String loadCommands = await eval('otool', <String>[
-    '-l',
-    '-arch',
-    'arm64',
-    pathToBinary,
-  ]);
-  if (!loadCommands.contains('__LLVM')) {
-    return false;
-  }
-  // Presence of the section may mean a bitcode marker was embedded (size=1), but there is no content.
-  if (!loadCommands.contains('size 0x0000000000000001')) {
-    return true;
-  }
-  // Check the false positives: size=1 wasn't referencing the __LLVM section.
-
-  bool emptyBitcodeMarkerFound = false;
-  //  Section
-  //  sectname __bundle
-  //  segname __LLVM
-  //  addr 0x003c4000
-  //  size 0x0042b633
-  //  offset 3932160
-  //  ...
-  final List<String> lines = LineSplitter.split(loadCommands).toList();
-  lines.asMap().forEach((int index, String line) {
-    if (line.contains('segname __LLVM') && lines.length - index - 1 > 3) {
-      emptyBitcodeMarkerFound |= lines
-        .skip(index - 1)
-        .take(4)
-        .any((String line) => line.contains(' size 0x0000000000000001'));
-    }
-  });
-  return !emptyBitcodeMarkerFound;
-}
-
 /// Creates and boots a new simulator, passes the new simulator's identifier to
 /// `testFunction`.
 ///

packages/flutter_tools/bin/podhelper.rb

@@ -65,6 +65,9 @@ def flutter_additional_ios_build_settings(target)
     # Skip other updates if it's not a Flutter plugin (transitive dependency).
     next unless target.dependencies.any? { |dependency| dependency.name == 'Flutter' }
 
+    # Bitcode is deprecated, Flutter.framework bitcode blob will have been stripped.
+    build_configuration.build_settings['ENABLE_BITCODE'] = 'NO'
+
     # Profile can't be derived from the CocoaPods build configuration. Use release framework (for linking only).
     configuration_engine_dir = build_configuration.type == :debug ? debug_framework_dir : release_framework_dir
     Dir.new(configuration_engine_dir).each_child do |xcframework_file|

packages/flutter_tools/bin/xcode_backend.dart

@@ -333,11 +333,6 @@ class Context {
       );
     }
 
-    String bitcodeFlag = '';
-    if (environment['ENABLE_BITCODE'] == 'YES' && environment['ACTION'] == 'install') {
-      bitcodeFlag = 'true';
-    }
-
     final List<String> flutterArgs = <String>[];
 
     if (verbose) {
@@ -365,7 +360,6 @@ class Context {
       '-dTreeShakeIcons=${environment['TREE_SHAKE_ICONS'] ?? ''}',
       '-dTrackWidgetCreation=${environment['TRACK_WIDGET_CREATION'] ?? ''}',
       '-dDartObfuscation=${environment['DART_OBFUSCATION'] ?? ''}',
-      '-dEnableBitcode=$bitcodeFlag',
       '-dAction=${environment['ACTION'] ?? ''}',
       '--ExtraGenSnapshotOptions=${environment['EXTRA_GEN_SNAPSHOT_OPTIONS'] ?? ''}',
       '--DartDefines=${environment['DART_DEFINES'] ?? ''}',

packages/flutter_tools/lib/src/base/build.dart

@@ -116,16 +116,11 @@ class AOTSnapshotter {
     DarwinArch? darwinArch,
     String? sdkRoot,
     List<String> extraGenSnapshotOptions = const <String>[],
-    required bool bitcode,
     String? splitDebugInfo,
     required bool dartObfuscation,
     bool quiet = false,
   }) async {
     assert(platform != TargetPlatform.ios || darwinArch != null);
-    if (bitcode && platform != TargetPlatform.ios) {
-      _logger.printError('Bitcode is only supported for iOS.');
-      return 1;
-    }
 
     if (!_isValidAotPlatform(platform, buildMode)) {
       _logger.printError('${getNameForTargetPlatform(platform)} does not support AOT compilation.');
@@ -244,7 +239,6 @@ class AOTSnapshotter {
         sdkRoot: sdkRoot,
         assemblyPath: assembly,
         outputPath: outputDir.path,
-        bitcode: bitcode,
         quiet: quiet,
         stripAfterBuild: stripAfterBuild,
         extractAppleDebugSymbols: extractAppleDebugSymbols
@@ -262,7 +256,6 @@ class AOTSnapshotter {
     String? sdkRoot,
     required String assemblyPath,
     required String outputPath,
-    required bool bitcode,
     required bool quiet,
     required bool stripAfterBuild,
     required bool extractAppleDebugSymbols
@@ -286,12 +279,10 @@ class AOTSnapshotter {
       ],
     ];
 
-    const String embedBitcodeArg = '-fembed-bitcode';
     final String assemblyO = _fileSystem.path.join(outputPath, 'snapshot_assembly.o');
 
     final RunResult compileResult = await _xcode.cc(<String>[
       ...commonBuildOptions,
-      if (bitcode) embedBitcodeArg,
       '-c',
       assemblyPath,
       '-o',
@@ -311,7 +302,6 @@ class AOTSnapshotter {
       '-Xlinker', '-rpath', '-Xlinker', '@executable_path/Frameworks',
       '-Xlinker', '-rpath', '-Xlinker', '@loader_path/Frameworks',
       '-install_name', '@rpath/App.framework/App',
-      if (bitcode) embedBitcodeArg,
       '-o', appLib,
       assemblyO,
     ];

packages/flutter_tools/lib/src/build_info.dart

@@ -942,9 +942,6 @@ const String kTargetPlatform = 'TargetPlatform';
 /// The define to control what target file is used.
 const String kTargetFile = 'TargetFile';
 
-/// The define to control whether the AOT snapshot is built with bitcode.
-const String kBitcodeFlag = 'EnableBitcode';
-
 /// Whether to enable or disable track widget creation.
 const String kTrackWidgetCreation = 'TrackWidgetCreation';
 

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

@@ -250,7 +250,6 @@ class AndroidAot extends AotElfBase {
       buildMode: buildMode,
       mainPath: environment.buildDir.childFile('app.dill').path,
       outputPath: output.path,
-      bitcode: false,
       extraGenSnapshotOptions: extraGenSnapshotOptions,
       splitDebugInfo: splitDebugInfo,
       dartObfuscation: dartObfuscation,

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

@@ -296,7 +296,6 @@ abstract class AotElfBase extends Target {
       buildMode: buildMode,
       mainPath: environment.buildDir.childFile('app.dill').path,
       outputPath: outputPath,
-      bitcode: false,
       extraGenSnapshotOptions: extraGenSnapshotOptions,
       splitDebugInfo: splitDebugInfo,
       dartObfuscation: dartObfuscation,

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

@@ -56,7 +56,6 @@ abstract class AotAssemblyBase extends Target {
     }
 
     final List<String> extraGenSnapshotOptions = decodeCommaSeparated(environment.defines, kExtraGenSnapshotOptions);
-    final bool bitcode = environment.defines[kBitcodeFlag] == 'true';
     final BuildMode buildMode = getBuildModeForName(environmentBuildMode);
     final TargetPlatform targetPlatform = getTargetPlatformForName(environmentTargetPlatform);
     final String? splitDebugInfo = environment.defines[kSplitDebugInfo];
@@ -101,7 +100,6 @@ abstract class AotAssemblyBase extends Target {
         outputPath: environment.fileSystem.path.join(buildOutputPath, getNameForDarwinArch(darwinArch)),
         darwinArch: darwinArch,
         sdkRoot: sdkRoot,
-        bitcode: bitcode,
         quiet: true,
         splitDebugInfo: splitDebugInfo,
         dartObfuscation: dartObfuscation,
@@ -287,9 +285,6 @@ abstract class UnpackIOS extends Target {
     if (archs == null) {
       throw MissingDefineException(kIosArchs, name);
     }
-    if (environment.defines[kBitcodeFlag] == null) {
-      throw MissingDefineException(kBitcodeFlag, name);
-    }
     _copyFramework(environment, sdkRoot);
 
     final File frameworkBinary = environment.outputDir.childDirectory('Flutter.framework').childFile('Flutter');
@@ -298,7 +293,9 @@ abstract class UnpackIOS extends Target {
       throw Exception('Binary $frameworkBinaryPath does not exist, cannot thin');
     }
     _thinFramework(environment, frameworkBinaryPath, archs);
-    _bitcodeStripFramework(environment, frameworkBinaryPath);
+    if (buildMode == BuildMode.release) {
+      _bitcodeStripFramework(environment, frameworkBinaryPath);
+    }
     _signFramework(environment, frameworkBinaryPath, buildMode);
   }
 
@@ -373,16 +370,14 @@ abstract class UnpackIOS extends Target {
     }
   }
 
-  /// Destructively strip bitcode from the framework, if needed.
+  /// Destructively strip bitcode from the framework. This can be removed
+  /// when the framework is no longer built with bitcode.
   void _bitcodeStripFramework(Environment environment, String frameworkBinaryPath) {
-    if (environment.defines[kBitcodeFlag] == 'true') {
-      return;
-    }
     final ProcessResult stripResult = environment.processManager.runSync(<String>[
       'xcrun',
       'bitcode_strip',
       frameworkBinaryPath,
-      '-m', // leave the bitcode marker.
+      '-r', // Delete the bitcode segment.
       '-o',
       frameworkBinaryPath,
     ]);
@@ -669,7 +664,6 @@ Future<void> _createStubAppFramework(File outputFile, Environment environment,
       for (String arch in iosArchNames ?? <String>{}) ...<String>['-arch', arch],
       stubSource.path,
       '-dynamiclib',
-      '-fembed-bitcode-marker',
       // Keep version in sync with AOTSnapshotter flag
       if (environmentType == EnvironmentType.physical)
         '-miphoneos-version-min=11.0'

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

@@ -285,7 +285,6 @@ class CompileMacOSFramework extends Target {
       }
 
       pending.add(snapshotter.build(
-        bitcode: false,
         buildMode: buildMode,
         mainPath: environment.buildDir.childFile('app.dill').path,
         outputPath: environment.fileSystem.path.join(buildOutputPath, getNameForDarwinArch(darwinArch)),