Memory Leak to OpenFile Async in create_task?

Question

In C++ code I opened file by using create_task. But there is no close file. Is OpenFileAsync in create_task will close old file and open a new file in the operation? Otherwise a memory leak may be happened.  In Win32 we deal with this kind of reentry by close previous file handle first.

---

Charlie Chang L

Answer 1

Hi Charlie,

Your file will be closed when the stream accessing it is Closed. In C++, delete the stream (or DataReader or DataWriter) object.

--Rob

Answer 2

Hi Charlie,

Your file will be closed when the stream accessing it is Closed. In C++, delete the stream (or DataReader or DataWriter) object.

--Rob

So when I opened a file and then a stream, the file was closed, that is fine but the stream still live. The problem still in there. I do not know where to delete the stream. For example,

create_task(...).then([=](StorageFile^ file){    
  create_task(file->OpenAsync(...)).then(=)(IRandomAccessStream^ stream)   {         
     if (stream != nullptr) {            
        ME->SetSource(stream, file->ContentType);         
     }    
  }
}

You see, when I reentry this code clip, there is no place to delete stream!

Is stream like ref new type that can be auto removed?

 

---

Charlie Chang L

Answer 3

add "delete stream" after the line ME->SetSource(...);

see this sample: http://code.msdn.microsoft.com/windowsapps/File-access-sample-d723e597/sourcecode?fileId=44739&pathId=1519713705

      create_task(file->OpenAsync(FileAccessMode::Read)).then([this, file](task<IRandomAccessStream^> task) 
        { 
            try 
            { 
                IRandomAccessStream^ readStream = task.get(); 
                UINT64 const size = readStream->Size; 
                if (size <= MAXUINT32) 
                { 
                    DataReader^ dataReader = ref new DataReader(readStream); 
                    create_task(dataReader->LoadAsync(static_cast<UINT32>(size))).then([this, file, dataReader](unsigned int numBytesLoaded) 
                    { 
                        String^ fileContent = dataReader->ReadString(numBytesLoaded); 
                        delete dataReader; // As a best practice, explicitly close the dataReader resource as soon as it is no longer needed. 
                        OutputTextBlock->Text = "The following text was read from '" + file->Name + "' using a stream:\n\n" + fileContent; 
                    }); 
                } 
                else 
                { 
                    delete readStream; // As a best practice, explicitly close the readStream resource as soon as it is no longer needed. 
                    OutputTextBlock->Text = "File " + file->Name + " is too big for LoadAsync to load in a single chunk. Files larger than 4GB need to be broken into multiple chunks to be loaded by LoadAsync."; 
                } 
            } 
            catch(COMException^ ex) 
            { 
                rootPage->HandleFileNotFoundException(ex); 
            } 
        });