pkgs/objective_c/test/util.dart

// 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.

// ignore_for_file: avoid_catching_errors

import 'dart:ffi';

import 'package:ffi/ffi.dart';
import 'package:native_test_helpers/native_test_helpers.dart';
import 'package:objective_c/objective_c.dart';
import 'package:objective_c/src/internal.dart'
    as internal_for_testing
    show isValidClass;
import 'package:path/path.dart' as p;

final _executeInternalCommand = () {
  try {
    return DynamicLibrary.process()
        .lookup<NativeFunction<Void Function(Pointer<Char>, Pointer<Void>)>>(
          'Dart_ExecuteInternalCommand',
        )
        .asFunction<void Function(Pointer<Char>, Pointer<Void>)>();
  } on ArgumentError {
    return null;
  }
}();

bool canDoGC = _executeInternalCommand != null;

void doGC() {
  final gcNow = 'gc-now'.toNativeUtf8();
  _executeInternalCommand!(gcNow.cast(), nullptr);
  calloc.free(gcNow);
}

@Native<Int Function(Pointer<Void>)>(isLeaf: true, symbol: 'isReadableMemory')
external int _isReadableMemory(Pointer<Void> ptr);

@Native<Uint64 Function(Pointer<Void>)>(
  isLeaf: true,
  symbol: 'getObjectRetainCount',
)
external int _getObjectRetainCount(Pointer<Void> object);

int objectRetainCount(Pointer<ObjCObject> object) {
  if (_isReadableMemory(object.cast()) == 0) return 0;
  final header = object.cast<Uint64>().value;

  // package:objective_c's isValidObject function internally calls
  // object_getClass then isValidClass. But object_getClass can occasionally
  // crash for invalid objects. This masking logic is a simplified version of
  // what object_getClass does internally. This is less likely to crash, but
  // more likely to break due to ObjC runtime updates, which is a reasonable
  // trade off to make in tests where we're explicitly calling it many times
  // on invalid objects. In package:objective_c's case, it doesn't matter so
  // much if isValidObject crashes, since it's a best effort attempt to give a
  // nice stack trace before the real crash, but it would be a problem if
  // isValidObject broke due to a runtime update.
  // These constants are the ISA_MASK macro defined in runtime/objc-private.h.
  const maskX64 = 0x00007ffffffffff8;
  const maskArm = 0x00000001fffffff8;
  final mask = Abi.current() == Abi.macosX64 ? maskX64 : maskArm;
  final clazz = Pointer<ObjCObject>.fromAddress(header & mask);

  if (!internal_for_testing.isValidClass(clazz)) return 0;
  return _getObjectRetainCount(object.cast());
}

String pkgDir = findPackageRoot('objective_c').toFilePath();

// TODO(https://github.com/dart-lang/native/issues/1068): Remove this.
String testDylib = p.join(pkgDir, 'test', 'objective_c.dylib');