[native_toolchain_c] Default handling for PIC/PIE compiler flags (#121)

Author: blaugold

pkgs/native_toolchain_c/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.2.2
+
+- Generate position independent code for libraries by default and add
+  `pic` option to control this behavior.
+
 ## 0.2.1
 
 - Added `defines` for specifying custom defines.

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

@@ -81,6 +81,20 @@ class CBuilder implements Builder {
   /// Defaults to `true`.
   final bool ndebugDefine;
 
+  /// Whether the compiler will emit position independent code.
+  ///
+  /// When set to `true`, libraries will be compiled with `-fPIC` and
+  /// executables with `-fPIE`. Accordingly the corresponding parameter of the
+  /// [executable] constructor is named `pie`.
+  ///
+  /// When set to `null`, the default behavior of the compiler will be used.
+  ///
+  /// This option has no effect when building for Windows, where generation of
+  /// position independent code is not configurable.
+  ///
+  /// Defaults to `true` for libraries and `false` for executables.
+  final bool? pic;
+
   CBuilder.library({
     required this.name,
     required this.assetId,
@@ -90,6 +104,7 @@ class CBuilder implements Builder {
     this.defines = const {},
     this.buildModeDefine = true,
     this.ndebugDefine = true,
+    this.pic = true,
   }) : _type = _CBuilderType.library;
 
   CBuilder.executable({
@@ -99,9 +114,11 @@ class CBuilder implements Builder {
     this.defines = const {},
     this.buildModeDefine = true,
     this.ndebugDefine = true,
+    bool? pie = false,
   })  : _type = _CBuilderType.executable,
         assetId = null,
-        installName = null;
+        installName = null,
+        pic = pie;
 
   /// Runs the C Compiler with on this C build spec.
   ///
@@ -148,6 +165,7 @@ class CBuilder implements Builder {
           if (ndebugDefine && buildConfig.buildMode != BuildMode.debug)
             'NDEBUG': null,
         },
+        pic: pic,
       );
       await task.run();
     }

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

@@ -25,14 +25,15 @@ class RunCBuilder {
   final Uri outDir;
   final Target target;
 
-  /// The install of the [dynamicLibrary].
+  /// The install name of the [dynamicLibrary].
   ///
   /// Can be inspected with `otool -D <path-to-dylib>`.
   ///
   /// Can be modified with `install_name_tool`.
   final Uri? installName;
 
   final Map<String, String?> defines;
+  final bool? pic;
 
   RunCBuilder({
     required this.buildConfig,
@@ -43,6 +44,7 @@ class RunCBuilder {
     this.staticLibrary,
     this.installName,
     this.defines = const {},
+    this.pic,
   })  : outDir = buildConfig.outDir,
         target = buildConfig.target,
         assert([executable, dynamicLibrary, staticLibrary]
@@ -145,6 +147,20 @@ class RunCBuilder {
           '-o',
           outDir.resolve('out.o').toFilePath(),
         ],
+        if (pic != null)
+          if (pic!) ...[
+            if (dynamicLibrary != null) '-fPIC',
+            // Using PIC for static libraries allows them to be linked into
+            // any executable, but it is not necessarily the best option in
+            // terms of overhead. We would have to know wether the target into
+            // which the static library is linked is PIC, PIE or neither. Then
+            // we could use the same option for the static library.
+            if (staticLibrary != null) '-fPIC',
+            if (executable != null) '-fPIE',
+          ] else ...[
+            '-fno-PIC',
+            '-fno-PIE',
+          ],
         for (final MapEntry(key: name, :value) in defines.entries)
           if (value == null) '-D$name' else '-D$name=$value',
       ],

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: 0.2.1
+version: 0.2.2
 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

@@ -41,7 +41,7 @@ void main() {
 
   for (final linkMode in LinkMode.values) {
     for (final target in targets) {
-      test('Cbuilder $linkMode library $target', () async {
+      test('CBuilder $linkMode library $target', () async {
         await inTempDir((tempUri) async {
           final libUri = await buildLib(
             tempUri,
@@ -77,7 +77,7 @@ void main() {
     }
   }
 
-  test('Cbuilder API levels binary difference', () async {
+  test('CBuilder API levels binary difference', () async {
     const target = Target.androidArm64;
     const linkMode = LinkMode.dynamic;
     const apiLevel1 = flutterAndroidNdkVersionLowestSupported;

pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_ios_test.dart

@@ -50,7 +50,7 @@ void main() {
             Uri.file('@executable_path/Frameworks/$libName'),
         ]) {
           test(
-              'Cbuilder $linkMode library $targetIOSSdk $target'
+              'CBuilder $linkMode library $targetIOSSdk $target'
                       ' ${installName ?? ''}'
                   .trim(), () async {
             await inTempDir((tempUri) async {

pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_linux_host_test.dart

@@ -36,7 +36,7 @@ void main() {
 
   for (final linkMode in LinkMode.values) {
     for (final target in targets) {
-      test('Cbuilder $linkMode library $target', () async {
+      test('CBuilder $linkMode library $target', () async {
         await inTempDir((tempUri) async {
           final addCUri =
               packageUri.resolve('test/cbuilder/testfiles/add/src/add.c');

pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_macos_host_test.dart

@@ -36,7 +36,7 @@ void main() {
 
   for (final linkMode in LinkMode.values) {
     for (final target in targets) {
-      test('Cbuilder $linkMode library $target', () async {
+      test('CBuilder $linkMode library $target', () async {
         await inTempDir((tempUri) async {
           final addCUri =
               packageUri.resolve('test/cbuilder/testfiles/add/src/add.c');

pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_windows_host_test.dart

@@ -48,7 +48,7 @@ void main() {
 
   for (final linkMode in LinkMode.values) {
     for (final target in targets) {
-      test('Cbuilder $linkMode library $target', () async {
+      test('CBuilder $linkMode library $target', () async {
         await inTempDir((tempUri) async {
           final addCUri =
               packageUri.resolve('test/cbuilder/testfiles/add/src/add.c');