[native_toolchain_c] Add linking for Android (#2347)

Author: goderbauer

pkgs/native_toolchain_c/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.16.3
+
+* Support linking for Android.
+
 ## 0.16.2
 
 * Bump the SDK constraint to at least the one from `package:hooks` to fix

pkgs/native_toolchain_c/lib/src/cbuilder/clinker.dart

@@ -53,10 +53,12 @@ class CLinker extends CTool implements Linker {
     required LinkOutputBuilder output,
     required Logger? logger,
   }) async {
-    if (OS.current != OS.linux || input.config.code.targetOS != OS.linux) {
+    const supportedTargetOSs = [OS.linux, OS.android];
+    if (!supportedTargetOSs.contains(input.config.code.targetOS)) {
       throw UnsupportedError(
-        'Currently, only linux is supported for this '
-        'feature. See also https://github.com/dart-lang/native/issues/1376',
+        'This feature is only supported when targeting '
+        '${supportedTargetOSs.join(', ')}. '
+        'See also https://github.com/dart-lang/native/issues/1376',
       );
     }
     final outDir = input.outputDirectory;

pkgs/native_toolchain_c/lib/src/cbuilder/compiler_resolver.dart

@@ -240,81 +240,4 @@ class CompilerResolver {
       ],
     );
   }
-
-  Future<ToolInstance> resolveLinker() async {
-    final targetOS = codeConfig.targetOS;
-    final targetArchitecture = codeConfig.targetArchitecture;
-    // First, check if the launcher provided a direct path to the compiler.
-    var result = await _tryLoadLinkerFromInput();
-
-    // Then, try to detect on the host machine.
-    final tool = _selectLinker();
-    if (tool != null) {
-      result ??= await _tryLoadToolFromNativeToolchain(tool);
-    }
-
-    if (result != null) {
-      return result;
-    }
-
-    final errorMessage =
-        "No linker configured on host '${hostOS}_$hostArchitecture' with "
-        "target '${targetOS}_$targetArchitecture'.";
-    logger?.severe(errorMessage);
-    throw ToolError(errorMessage);
-  }
-
-  Future<ToolInstance?> _tryLoadLinkerFromInput() async {
-    final inputLdUri = codeConfig.cCompiler?.linker;
-    if (inputLdUri != null) {
-      assert(await File.fromUri(inputLdUri).exists());
-      logger?.finer(
-        'Using linker ${inputLdUri.toFilePath()} '
-        'from cCompiler.ld.',
-      );
-      final tools = await LinkerRecognizer(inputLdUri).resolve(logger: logger);
-      return tools.first;
-    }
-    logger?.finer('No linker set in cCompiler.ld.');
-    return null;
-  }
-
-  /// Select the right compiler for cross compiling to the specified target.
-  Tool? _selectLinker() {
-    final targetOS = codeConfig.targetOS;
-    final targetArchitecture = codeConfig.targetArchitecture;
-
-    if (targetOS == OS.macOS || targetOS == OS.iOS) return appleLd;
-    if (targetOS == OS.android) return androidNdkLld;
-    if (hostOS == OS.linux) {
-      if (Architecture.current == targetArchitecture) {
-        return lld;
-      }
-      switch (targetArchitecture) {
-        case Architecture.arm:
-          return armLinuxGnueabihfLd;
-        case Architecture.arm64:
-          return aarch64LinuxGnuLd;
-        case Architecture.ia32:
-          return i686LinuxGnuLd;
-        case Architecture.x64:
-          return x86_64LinuxGnuLd;
-        case Architecture.riscv64:
-          return riscv64LinuxGnuLd;
-      }
-    }
-
-    if (hostOS == OS.windows) {
-      switch (targetArchitecture) {
-        case Architecture.ia32:
-          return linkIA32;
-        case Architecture.arm64:
-          return linkArm64;
-        case Architecture.x64:
-          return msvcLink;
-      }
-    }
-
-    return null;
-  }
 }

pkgs/native_toolchain_c/lib/src/cbuilder/linker_options.dart

@@ -51,7 +51,7 @@ class LinkerOptions {
   }) : _linkerFlags = <String>[
          ...flags ?? [],
          '--strip-debug',
-         if (symbols != null) ...symbols.expand((e) => ['-u', e]),
+         if (symbols != null) ...symbols.map((e) => '-u,$e'),
        ].toList(),
        gcSections = true,
        _wholeArchiveSandwich = symbols == null,

pkgs/native_toolchain_c/lib/src/cbuilder/run_cbuilder.dart

@@ -96,8 +96,6 @@ class RunCBuilder {
 
   Future<Uri> archiver() async => (await _resolver.resolveArchiver()).uri;
 
-  Future<ToolInstance> linker() async => await _resolver.resolveLinker();
-
   Future<Uri> iosSdk(IOSSdk iosSdk, {required Logger? logger}) async {
     if (iosSdk == IOSSdk.iPhoneOS) {
       return (await iPhoneOSSdk.defaultResolver!.resolve(
@@ -119,9 +117,7 @@ class RunCBuilder {
       compiler.uri.resolve('../sysroot/');
 
   Future<void> run() async {
-    final toolInstance_ = linkerOptions != null
-        ? await linker()
-        : await compiler();
+    final toolInstance_ = await compiler();
     final tool = toolInstance_.tool;
     if (tool.isClangLike || tool.isLdLike) {
       await runClangLike(tool: toolInstance_);
@@ -333,10 +329,7 @@ class RunCBuilder {
             // During bundling code assets are all placed in the same directory.
             // Setting this rpath allows the binary to find other code assets
             // it is linked against.
-            if (linkerOptions != null)
-              '-rpath=\$ORIGIN'
-            else
-              '-Wl,-rpath=\$ORIGIN',
+            '-Wl,-rpath=\$ORIGIN',
           for (final directory in libraryDirectories)
             '-L${directory.toFilePath()}',
           for (final library in libraries) '-l$library',

pkgs/native_toolchain_c/pubspec.yaml

@@ -1,7 +1,7 @@
 name: native_toolchain_c
 description: >-
   A library to invoke the native C compiler installed on the host machine.
-version: 0.16.2
+version: 0.16.3
 repository: https://github.com/dart-lang/native/tree/main/pkgs/native_toolchain_c
 
 topics:

pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_android_test.dart

@@ -7,7 +7,6 @@ import 'dart:io';
 import 'package:code_assets/code_assets.dart';
 import 'package:hooks/hooks.dart';
 import 'package:native_toolchain_c/native_toolchain_c.dart';
-import 'package:native_toolchain_c/src/utils/run_process.dart';
 import 'package:test/test.dart';
 
 import '../helpers.dart';
@@ -21,20 +20,6 @@ void main() {
     Architecture.riscv64,
   ];
 
-  const objdumpFileFormat = {
-    Architecture.arm: 'elf32-littlearm',
-    Architecture.arm64: 'elf64-littleaarch64',
-    Architecture.ia32: 'elf32-i386',
-    Architecture.x64: 'elf64-x86-64',
-    Architecture.riscv64: 'elf64-littleriscv',
-  };
-
-  /// From https://docs.flutter.dev/reference/supported-platforms.
-  const flutterAndroidNdkVersionLowestSupported = 21;
-
-  /// From https://docs.flutter.dev/reference/supported-platforms.
-  const flutterAndroidNdkVersionHighestSupported = 34;
-
   const optimizationLevels = OptimizationLevel.values;
   var selectOptimizationLevel = 0;
 
@@ -58,21 +43,7 @@ void main() {
             linkMode,
             optimizationLevel: optimizationLevel,
           );
-          if (Platform.isLinux) {
-            final machine = await readelfMachine(libUri.path);
-            expect(machine, contains(readElfMachine[target]));
-          } else if (Platform.isMacOS) {
-            final result = await runProcess(
-              executable: Uri.file('objdump'),
-              arguments: ['-T', libUri.path],
-              logger: logger,
-            );
-            expect(result.exitCode, 0);
-            final machine = result.stdout
-                .split('\n')
-                .firstWhere((e) => e.contains('file format'));
-            expect(machine, contains(objdumpFileFormat[target]));
-          }
+          await expectMachineArchitecture(libUri, target);
           if (linkMode == DynamicLoadingBundled()) {
             await expectPageSize(libUri, 16 * 1024);
           }

pkgs/native_toolchain_c/test/clinker/build_testfiles.dart

@@ -13,9 +13,11 @@ import '../helpers.dart';
 Future<Uri> buildTestArchive(
   Uri tempUri,
   Uri tempUri2,
-  OS os,
-  Architecture architecture,
-) async {
+  OS targetOS,
+  Architecture architecture, {
+  int? androidTargetNdkApi, // Must be specified iff targetOS is OS.android.
+}) async {
+  assert((targetOS != OS.android) == (androidTargetNdkApi == null));
   final test1Uri = packageUri.resolve('test/clinker/testfiles/linker/test1.c');
   final test2Uri = packageUri.resolve('test/clinker/testfiles/linker/test2.c');
   if (!await File.fromUri(test1Uri).exists() ||
@@ -27,7 +29,6 @@ Future<Uri> buildTestArchive(
   final logMessages = <String>[];
   final logger = createCapturingLogger(logMessages);
 
-  assert(os == OS.linux); // Setup code input for other OSes.
   final buildInputBuilder = BuildInputBuilder()
     ..setupShared(
       packageName: name,
@@ -38,10 +39,13 @@ Future<Uri> buildTestArchive(
     ..config.setupBuild(linkingEnabled: false)
     ..addExtension(
       CodeAssetExtension(
-        targetOS: os,
+        targetOS: targetOS,
         targetArchitecture: architecture,
         linkModePreference: LinkModePreference.dynamic,
         cCompiler: cCompiler,
+        android: androidTargetNdkApi != null
+            ? AndroidCodeConfig(targetNdkApi: androidTargetNdkApi)
+            : null,
       ),
     );
 

pkgs/native_toolchain_c/test/clinker/objects_cross_android_test.dart

@@ -0,0 +1,30 @@
+// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:code_assets/code_assets.dart';
+import 'package:test/test.dart';
+
+import '../helpers.dart';
+import 'objects_helper.dart';
+
+void main() {
+  final architectures = [
+    Architecture.arm,
+    Architecture.arm64,
+    Architecture.ia32,
+    Architecture.x64,
+    Architecture.riscv64,
+  ];
+
+  const targetOS = OS.android;
+
+  for (final apiLevel in [
+    flutterAndroidNdkVersionLowestSupported,
+    flutterAndroidNdkVersionHighestSupported,
+  ]) {
+    group('Android API$apiLevel', () {
+      runObjectsTests(targetOS, architectures, androidTargetNdkApi: apiLevel);
+    });
+  }
+}

pkgs/native_toolchain_c/test/clinker/objects_cross_test.dart

@@ -0,0 +1,32 @@
+// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+//TODO(mosuem): Enable for windows and mac.
+// See https://github.com/dart-lang/native/issues/1376.
+@TestOn('linux')
+library;
+
+import 'dart:io';
+
+import 'package:code_assets/code_assets.dart';
+import 'package:test/test.dart';
+
+import 'objects_helper.dart';
+
+void main() {
+  if (!Platform.isLinux) {
+    // Avoid needing status files on Dart SDK CI.
+    return;
+  }
+
+  final architectures = [
+    Architecture.arm,
+    Architecture.arm64,
+    Architecture.ia32,
+    Architecture.x64,
+    Architecture.riscv64,
+  ]..remove(Architecture.current);
+
+  runObjectsTests(OS.current, architectures);
+}