如何安全删除ATL DLL中的std :: thread

Question

I wrote an ATL DLL and I have problem with std::thread witch I used to run asyn method. I implemented method that performs operations asynchronously. The problem occurs when a client tries to remove the object class in which thread already done.

This is my code:

STDMETHODIMP CQRCodeGenerator::GenerateAsync(QRCodeTypeEnum QRCodeType, QRCodeFormatEnum QRCodeFormat, LONG QRCodePx, BSTR ImageFile)
{

if (ImageFile == nullptr) ImageFile = L"";

//stack to log file
OPFHelper::add_execute_method(this, L"CQRCodeGenerator::GenerateAsync",
    std::vector<std::wstring>{OPFHelper::ConvertToWSting((LONG)QRCodeType),
    OPFHelper::ConvertToWSting((LONG)QRCodeFormat), OPFHelper::ConvertToWSting((LONG)QRCodePx), ImageFile});

t = std::thread(&CQRCodeGenerator::run, this, QRCodeType, QRCodeFormat, QRCodePx, ImageFile);
return S_OK;
}

void CQRCodeGenerator::run(enum QRCodeTypeEnum QRCodeType, enum QRCodeFormatEnum QRCodeFormat, LONG QRCodePx, BSTR ImageFile)
{

 ......

Fire_OnGenerate(this,ImageFile, _pQRCode, _pInvoiceID, _pQRCodeMD5, _pKS,nullptr);
}   

1. std::thread is declared in .h file
2. when I reception event and I try delete obj QRCodeGenerator I get error.

I know that this is a problem with the removal of the thread of memory, because I carried out synchronous function Generate which did not give error.

But I don't know how Can I delete this thread and detect when Client wants to delete obj. The second thing it can not understand why there is a problem with releasing memory when thread-assistant no longer works.

Answer 1

Do you call std::thread::join() or detach() before destroying the thread? Otherwise the std::thread destructor is supposed to trigger terminate() and abort the program.

If something is owning the thread (as " client tries to remove the object class in which thread already done " suggests), the object might call t.join() in its destructor, for example.

Also note that you shouldn't destroy the object inside of Fire_OnGenerate - that is called in the scope of the running thread. So you would basically destroy a thread which is still running (it only can complete after Fire_OnGenerate returns back).