[native_toolchain_c] Support Module Definitions for linking on Windows (#2386)

Author: goderbauer

pkgs/native_toolchain_c/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.16.7
+
+* Support Module Definitions for linking on Windows.
+
 ## 0.16.6
 
 * Support linking for Windows.

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

@@ -38,6 +38,8 @@ class LinkerOptions {
   /// If null all symbols will be kept.
   final List<String>? _symbolsToKeep;
 
+  final bool _generateLinkerScript;
+
   /// Create linking options manually for fine-grained control.
   LinkerOptions.manual({
     List<String>? flags,
@@ -47,7 +49,8 @@ class LinkerOptions {
     Iterable<String>? symbolsToKeep,
   }) : _linkerFlags = flags ?? [],
        gcSections = gcSections ?? true,
-       _symbolsToKeep = symbolsToKeep?.toList(growable: false);
+       _symbolsToKeep = symbolsToKeep?.toList(growable: false),
+       _generateLinkerScript = false;
 
   /// Create linking options to tree-shake symbols from the input files.
   ///
@@ -59,7 +62,8 @@ class LinkerOptions {
   }) : _linkerFlags = flags?.toList(growable: false) ?? [],
        _symbolsToKeep = symbols?.toList(growable: false),
        gcSections = true,
-       linkerScript = _createLinkerScript(symbols);
+       linkerScript = null,
+       _generateLinkerScript = symbols != null;
 
   Iterable<String> _toLinkerSyntax(Tool linker, Iterable<String> flagList) {
     if (linker.isClangLike) {
@@ -70,22 +74,6 @@ class LinkerOptions {
       throw UnsupportedError('Linker flags for $linker are not supported');
     }
   }
-
-  static Uri? _createLinkerScript(Iterable<String>? symbols) {
-    if (symbols == null) return null;
-    final tempDir = Directory.systemTemp.createTempSync();
-    final symbolsFileUri = tempDir.uri.resolve('symbols.lds');
-    final symbolsFile = File.fromUri(symbolsFileUri)..createSync();
-    symbolsFile.writeAsStringSync('''
-{
-  global:
-    ${symbols.map((e) => '$e;').join('\n    ')}
-  local:
-    *;
-};
-''');
-    return symbolsFileUri;
-  }
 }
 
 extension LinkerOptionsExt on LinkerOptions {
@@ -145,7 +133,9 @@ extension LinkerOptionsExt on LinkerOptions {
             if (stripDebug) '--strip-debug',
             if (gcSections) '--gc-sections',
             if (linkerScript != null)
-              '--version-script=${linkerScript!.toFilePath()}',
+              '--version-script=${linkerScript!.toFilePath()}'
+            else if (_generateLinkerScript && _symbolsToKeep != null)
+              '--version-script=${_createClangLikeLinkScript(_symbolsToKeep)}',
             if (wholeArchiveSandwich) '--no-whole-archive',
           ]),
         ];
@@ -169,7 +159,38 @@ extension LinkerOptionsExt on LinkerOptions {
               '/INCLUDE:${targetArch == Architecture.ia32 ? '_' : ''}$symbol',
         ) ??
         [],
+    if (linkerScript != null)
+      '/DEF:${linkerScript!.toFilePath()}'
+    else if (_generateLinkerScript && _symbolsToKeep != null)
+      '/DEF:${_createClLinkScript(_symbolsToKeep)}',
     if (stripDebug) '/PDBSTRIPPED',
     if (gcSections) '/OPT:REF',
   ];
+
+  static String _createClangLikeLinkScript(Iterable<String> symbols) {
+    final tempDir = Directory.systemTemp.createTempSync();
+    final symbolsFileUri = tempDir.uri.resolve('symbols.lds');
+    final symbolsFile = File.fromUri(symbolsFileUri)..createSync();
+    symbolsFile.writeAsStringSync('''
+{
+  global:
+    ${symbols.map((e) => '$e;').join('\n    ')}
+  local:
+    *;
+};
+''');
+    return symbolsFileUri.toFilePath();
+  }
+
+  static String _createClLinkScript(Iterable<String> symbols) {
+    final tempDir = Directory.systemTemp.createTempSync();
+    final symbolsFileUri = tempDir.uri.resolve('symbols.def');
+    final symbolsFile = File.fromUri(symbolsFileUri)..createSync();
+    symbolsFile.writeAsStringSync('''
+LIBRARY MyDLL
+EXPORTS
+${symbols.map((s) => '    $s').join('\n')}      
+''');
+    return symbolsFileUri.toFilePath();
+  }
 }

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: 0.16.6
+version: 0.16.7
 repository: https://github.com/dart-lang/native/tree/main/pkgs/native_toolchain_c
 
 topics:

pkgs/native_toolchain_c/test/clinker/build_testfiles.dart

@@ -15,6 +15,7 @@ Future<Uri> buildTestArchive(
   Uri tempUri2,
   OS targetOS,
   Architecture architecture, {
+  List<Uri>? extraSources,
   int? androidTargetNdkApi, // Must be specified iff targetOS is OS.android.
   int? macOSTargetVersion, // Must be specified iff targetOS is OS.macos.
   int? iOSTargetVersion, // Must be specified iff targetOS is OS.iOS.
@@ -77,7 +78,11 @@ Future<Uri> buildTestArchive(
   final cbuilder = CBuilder.library(
     name: name,
     assetName: '',
-    sources: [test1Uri.toFilePath(), test2Uri.toFilePath()],
+    sources: [
+      test1Uri.toFilePath(),
+      test2Uri.toFilePath(),
+      ...?extraSources?.map((src) => src.toFilePath()),
+    ],
     linkModePreference: LinkModePreference.static,
     buildMode: BuildMode.release,
   );

pkgs/native_toolchain_c/test/clinker/testfiles/linker/symbols.def

@@ -0,0 +1,3 @@
+LIBRARY MyDLL
+EXPORTS
+    my_other_func

pkgs/native_toolchain_c/test/clinker/testfiles/linker/test3.c

@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+// Explicitly not marked for export.
+void my_unexported_func()
+{
+  printf("Hello unexported World");
+}

pkgs/native_toolchain_c/test/clinker/treeshake_helper.dart

@@ -39,9 +39,9 @@ void runTreeshakeTests(
       symbolsToKeep: ['my_other_func'],
       stripDebug: true,
       gcSections: true,
-      linkerScript: packageUri.resolve(
-        'test/clinker/testfiles/linker/symbols.lds',
-      ),
+      linkerScript: targetOS == OS.windows
+          ? packageUri.resolve('test/clinker/testfiles/linker/symbols.def')
+          : packageUri.resolve('test/clinker/testfiles/linker/symbols.lds'),
     ),
   );
   CLinker linkerAuto(List<String> sources) => CLinker.library(

pkgs/native_toolchain_c/test/clinker/windows_module_definition_cross_test.dart

@@ -0,0 +1,26 @@
+// Copyright (c) 2024, 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.
+
+@TestOn('windows')
+library;
+
+import 'dart:io';
+
+import 'package:code_assets/code_assets.dart';
+import 'package:test/test.dart';
+
+import '../helpers.dart';
+import 'windows_module_definition_helper.dart';
+
+void main() {
+  if (!Platform.isWindows) {
+    // Avoid needing status files on Dart SDK CI.
+    return;
+  }
+
+  final architectures = supportedArchitecturesFor(OS.current)
+    // See windows_module_definition_test.dart for current arch.
+    ..remove(Architecture.current);
+  runWindowsModuleDefinitionTests(architectures);
+}

pkgs/native_toolchain_c/test/clinker/windows_module_definition_helper.dart

@@ -0,0 +1,83 @@
+// 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 '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:test/test.dart';
+
+import '../helpers.dart';
+import 'build_testfiles.dart';
+
+void runWindowsModuleDefinitionTests(List<Architecture> architectures) {
+  const name = 'mylibname';
+  const targetOS = OS.windows;
+
+  for (final architecture in architectures) {
+    test(
+      'Module definition script can export unexported function ($architecture)',
+      () async {
+        final tempUri = await tempDirForTest();
+        final tempUri2 = await tempDirForTest();
+
+        final uri = await buildTestArchive(
+          tempUri,
+          tempUri2,
+          targetOS,
+          architecture,
+          extraSources: [
+            packageUri.resolve('test/clinker/testfiles/linker/test3.c'),
+          ],
+        );
+
+        final linkInputBuilder = LinkInputBuilder()
+          ..setupShared(
+            packageName: 'testpackage',
+            packageRoot: tempUri,
+            outputFile: tempUri.resolve('output.json'),
+            outputDirectoryShared: tempUri2,
+          )
+          ..setupLink(assets: [], recordedUsesFile: null)
+          ..addExtension(
+            CodeAssetExtension(
+              targetOS: targetOS,
+              targetArchitecture: architecture,
+              linkModePreference: LinkModePreference.dynamic,
+              cCompiler: cCompiler,
+            ),
+          );
+
+        final linkInput = linkInputBuilder.build();
+        final linkOutput = LinkOutputBuilder();
+
+        printOnFailure(linkInput.config.code.cCompiler.toString());
+        printOnFailure(Platform.environment.keys.toList().toString());
+        await CLinker.library(
+          name: name,
+          assetName: '',
+          linkerOptions: LinkerOptions.treeshake(
+            symbols: ['my_func', 'my_unexported_func'],
+          ),
+          sources: [uri.toFilePath()],
+        ).run(input: linkInput, output: linkOutput, logger: logger);
+
+        final codeAssets = LinkOutput(linkOutput.json).assets.code;
+        expect(codeAssets, hasLength(1));
+        final asset = codeAssets.first;
+        expect(asset, isA<CodeAsset>());
+        final symbols = await readSymbols(asset, targetOS);
+        final skipReason = symbols == null
+            ? 'tool to extract symbols unavailable'
+            : false;
+        expect(symbols, contains('my_func'), skip: skipReason);
+        // Module Definition file causes my_unexported_func to be exported even
+        // though it wasn't marked for export.
+        expect(symbols, contains('my_unexported_func'), skip: skipReason);
+        expect(symbols, isNot(contains('my_other_func')), skip: skipReason);
+      },
+    );
+  }
+}

pkgs/native_toolchain_c/test/clinker/windows_module_definition_test.dart

@@ -0,0 +1,21 @@
+// Copyright (c) 2024, 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.
+
+@TestOn('windows')
+library;
+
+import 'dart:io';
+
+import 'package:code_assets/code_assets.dart';
+import 'package:test/test.dart';
+
+import 'windows_module_definition_helper.dart';
+
+void main() {
+  if (!Platform.isWindows) {
+    // Avoid needing status files on Dart SDK CI.
+    return;
+  }
+  runWindowsModuleDefinitionTests([Architecture.current]);
+}