MacOS AudioHardwareSystem内存泄漏：新CoreAudio API如何避免泄漏？

我喜爱新CoreAudio API的简洁语法，但它存在严重的内存泄漏问题。请问有没有办法不用退回旧API就能避免这个泄漏？

问题重现代码（存在内存泄漏） #

func coreAudioProcessLeak() async throws {
    for process in try AudioHardwareSystem.shared.processes {
        print(try process.bundleID as Any)
    }
}

已通过Instruments确认，泄漏点指向for process in try AudioHardwareSystem.shared.processes这一行。

无泄漏但写法繁琐的旧API实现 #

func coreAudioProcessNoLeak() async throws {

    var listAddr = AudioObjectPropertyAddress(
        mSelector: kAudioHardwarePropertyProcessObjectList,
        mScope:    kAudioObjectPropertyScopeGlobal,
        mElement:  kAudioObjectPropertyElementMain
    )
    
    var listBytes: UInt32 = 0
    var status = AudioObjectGetPropertyDataSize(
        AudioObjectID(kAudioObjectSystemObject),
        &listAddr,
        0,
        nil,
        &listBytes
    )
    guard status == noErr else { throw NSError(
        domain: NSOSStatusErrorDomain, code: Int(status), userInfo: nil) }
    guard listBytes > 0 else { return }
    
    let count = Int(listBytes) / MemoryLayout<AudioObjectID>.stride
    var procIDs = Array<AudioObjectID>(repeating: 0, count: count)
    
    var tmpBytes = listBytes
    status = AudioObjectGetPropertyData(
        AudioObjectID(kAudioObjectSystemObject),
        &listAddr,
        0,
        nil,
        &tmpBytes,
        &procIDs
    )
    guard status == noErr else { throw NSError(
        domain: NSOSStatusErrorDomain, code: Int(status), userInfo: nil) }
    

    for procID in procIDs {
        var bidAddr = AudioObjectPropertyAddress(
            mSelector: kAudioProcessPropertyBundleID,
            mScope:    kAudioObjectPropertyScopeGlobal,
            mElement:  kAudioObjectPropertyElementMain
        )
        
        // 该属性的载荷为CFStringRef
        var bidBytes: UInt32 = UInt32(MemoryLayout<CFString?>.size)
        var cfStr: CFString? = nil
        let err = withUnsafeMutablePointer(to: &cfStr) { cfStr in
            AudioObjectGetPropertyData(
                procID,
                &bidAddr,
                0,
                nil,
                &bidBytes,
                cfStr
            )
        }

        if err == noErr, let cfStr {
            print(cfStr as String)
        }
    }
}

无需退回旧API的临时修复方案 #

这个泄漏属于Apple新CoreAudio API的底层实现问题，目前可以通过以下两种方式临时规避：

• 将processes序列转为数组后遍历
  通过Array(try AudioHardwareSystem.shared.processes)先将序列转为数组，明确管理所有Process实例的生命周期，避免迭代过程中内存无法及时释放：

  func coreAudioProcessFixed1() async throws {
      let processes = Array(try AudioHardwareSystem.shared.processes)
      for process in processes {
          print(try process.bundleID as Any)
      }
  }
  

• 在循环内添加自动释放池
  利用autoreleasepool包裹每次迭代的代码，强制释放当前循环中创建的临时对象，解决内存累积问题：

  func coreAudioProcessFixed2() async throws {
      for process in try AudioHardwareSystem.shared.processes {
          autoreleasepool {
              print(try process.bundleID as Any)
          }
      }
  }
  

如果以上方法仍无效，建议同时向Apple提交Bug Report，督促官方修复API的内存泄漏问题。

内容的提问来源于stack exchange，提问作者Devin Roth