ffigen: Don't generate setters for constant globals (#828)

pkgs/ffigen/CHANGELOG.md

@@ -4,6 +4,7 @@
 bindings to **not** be generated by default, since it may result in invalid
 bindings if the compiler makes a wrong guess. A flag `--ignore-source-errors` (or yaml config `ignore-source-errors: true`)
 must be passed to change this behaviour.
+- __Breaking change__: Stop generating setters for global variables marked `const` in C.
 
 ## 10.0.0
 

pkgs/ffigen/lib/src/code_generator/global.dart

@@ -22,6 +22,7 @@ import 'writer.dart';
 class Global extends LookUpBinding {
   final Type type;
   final bool exposeSymbolAddress;
+  final bool constant;
 
   Global({
     super.usr,
@@ -30,6 +31,7 @@ class Global extends LookUpBinding {
     required this.type,
     super.dartDoc,
     this.exposeSymbolAddress = false,
+    this.constant = false,
   });
 
   @override
@@ -55,8 +57,10 @@ class Global extends LookUpBinding {
       }
     } else {
       s.write('$dartType get $globalVarName => $pointerName.value;\n\n');
-      s.write(
-          'set $globalVarName($dartType value) => $pointerName.value = value;\n\n');
+      if (!constant) {
+        s.write(
+            'set $globalVarName($dartType value) => $pointerName.value = value;\n\n');
+      }
     }
 
     if (exposeSymbolAddress) {

pkgs/ffigen/lib/src/header_parser/clang_bindings/clang_bindings.dart

@@ -626,6 +626,23 @@ class Clang {
   late final _clang_getCanonicalType =
       _clang_getCanonicalTypePtr.asFunction<CXType Function(CXType)>();
 
+  /// Determine whether a CXType has the "const" qualifier set,
+  /// without looking through typedefs that may have added "const" at a
+  /// different level.
+  int clang_isConstQualifiedType(
+    CXType T,
+  ) {
+    return _clang_isConstQualifiedType(
+      T,
+    );
+  }
+
+  late final _clang_isConstQualifiedTypePtr =
+      _lookup<ffi.NativeFunction<ffi.UnsignedInt Function(CXType)>>(
+          'clang_isConstQualifiedType');
+  late final _clang_isConstQualifiedType =
+      _clang_isConstQualifiedTypePtr.asFunction<int Function(CXType)>();
+
   /// Determine whether a  CXCursor that is a macro, is
   /// function like.
   int clang_Cursor_isMacroFunctionLike(

pkgs/ffigen/lib/src/header_parser/sub_parsers/var_parser.dart

@@ -25,7 +25,8 @@ Global? parseVarDeclaration(clang_types.CXCursor cursor) {
 
   _logger.fine('++++ Adding Global: ${cursor.completeStringRepr()}');
 
-  final type = cursor.type().toCodeGenType();
+  final cType = cursor.type();
+  final type = cType.toCodeGenType();
   if (type.baseType is UnimplementedType) {
     _logger.fine('---- Removed Global, reason: unsupported type: '
         '${cursor.completeStringRepr()}');
@@ -46,6 +47,7 @@ Global? parseVarDeclaration(clang_types.CXCursor cursor) {
     type: type,
     dartDoc: getCursorDocComment(cursor),
     exposeSymbolAddress: config.functionDecl.shouldIncludeSymbolAddress(name),
+    constant: cType.isConstQualified,
   );
   bindingsIndex.addGlobalVarToSeen(usr, global);
   return global;

pkgs/ffigen/lib/src/header_parser/utils.dart

@@ -301,6 +301,10 @@ extension CXTypeExt on clang_types.CXType {
         '(Type) spelling: ${spelling()}, kind: ${kind()}, kindSpelling: ${kindSpelling()}';
     return s;
   }
+
+  bool get isConstQualified {
+    return clang.clang_isConstQualifiedType(this) != 0;
+  }
 }
 
 extension CXStringExt on clang_types.CXString {

pkgs/ffigen/test/code_generator_tests/code_generator_test.dart

@@ -250,6 +250,7 @@ void main() {
                 SupportedNativeType.Float,
               ),
             ),
+            constant: true,
           ),
           structSome,
           Global(

pkgs/ffigen/test/code_generator_tests/expected_bindings/_expected_global_bindings.dart

@@ -29,8 +29,6 @@ class Bindings {
 
   ffi.Pointer<ffi.Float> get test2 => _test2.value;
 
-  set test2(ffi.Pointer<ffi.Float> value) => _test2.value = value;
-
   late final ffi.Pointer<ffi.Pointer<Some>> _test5 =
       _lookup<ffi.Pointer<Some>>('test5');
 

pkgs/ffigen/test/header_parser_tests/globals.h

@@ -7,7 +7,10 @@
 
 bool coolGlobal;
 int32_t myInt;
-int32_t *aGlobalPointer;
+int32_t *aGlobalPointer0;
+int32_t *const aGlobalPointer1;
+const int32_t *aGlobalPointer2;
+const int32_t *const aGlobalPointer3;
 long double longDouble;
 long double *pointerToLongDouble;
 

pkgs/ffigen/test/header_parser_tests/globals_test.dart

@@ -35,6 +35,7 @@ ${strings.globals}:
       - pointerToLongDouble
       - globalStruct
 ${strings.compilerOpts}: '-Wno-nullability-completeness'
+${strings.ignoreSourceErrors}: true
         '''),
       );
     });
@@ -48,8 +49,14 @@ ${strings.compilerOpts}: '-Wno-nullability-completeness'
           expected.getBindingAsString('coolGlobal'));
       expect(actual.getBindingAsString('myInt'),
           expected.getBindingAsString('myInt'));
-      expect(actual.getBindingAsString('aGlobalPointer'),
-          expected.getBindingAsString('aGlobalPointer'));
+      expect(actual.getBindingAsString('aGlobalPointer0'),
+          expected.getBindingAsString('aGlobalPointer0'));
+      expect(actual.getBindingAsString('aGlobalPointer1'),
+          expected.getBindingAsString('aGlobalPointer1'));
+      expect(actual.getBindingAsString('aGlobalPointer2'),
+          expected.getBindingAsString('aGlobalPointer2'));
+      expect(actual.getBindingAsString('aGlobalPointer3'),
+          expected.getBindingAsString('aGlobalPointer3'));
     });
 
     test('Ignore global values', () {
@@ -60,6 +67,18 @@ ${strings.compilerOpts}: '-Wno-nullability-completeness'
       expect(() => actual.getBindingAsString('pointerToLongDouble'),
           throwsA(TypeMatcher<NotFoundException>()));
     });
+
+    test('identifies constant globals', () {
+      final globalPointers = [
+        for (var i = 0; i < 4; i++)
+          actual.getBinding('aGlobalPointer$i') as Global,
+      ];
+
+      expect(globalPointers[0].constant, isFalse); // int32_t*
+      expect(globalPointers[1].constant, isTrue); // int32_t* const
+      expect(globalPointers[2].constant, isFalse); // const int32_t*
+      expect(globalPointers[3].constant, isTrue); // const int32_t* const
+    });
   });
 }
 
@@ -76,8 +95,25 @@ Library expectedLibrary() {
       ),
       Global(
         type: PointerType(NativeType(SupportedNativeType.Int32)),
-        name: 'aGlobalPointer',
+        name: 'aGlobalPointer0',
+        exposeSymbolAddress: true,
+      ),
+      Global(
+        type: PointerType(NativeType(SupportedNativeType.Int32)),
+        name: 'aGlobalPointer1',
+        exposeSymbolAddress: true,
+        constant: true,
+      ),
+      Global(
+        type: PointerType(NativeType(SupportedNativeType.Int32)),
+        name: 'aGlobalPointer2',
+        exposeSymbolAddress: true,
+      ),
+      Global(
+        type: PointerType(NativeType(SupportedNativeType.Int32)),
+        name: 'aGlobalPointer3',
         exposeSymbolAddress: true,
+        constant: true,
       ),
       globalStruct,
       Global(

pkgs/ffigen/tool/libclang_config.yaml

@@ -94,6 +94,7 @@ functions:
     - clang_Cursor_getArgument
     - clang_getNumArgTypes
     - clang_getArgType
+    - clang_isConstQualifiedType
     - clang_isFunctionTypeVariadic
     - clang_Cursor_getStorageClass
     - clang_getCursorResultType