ATL / WTL / STL

#include <algorithm>
#include <fstream>
#include <sstream>

int main()
{
	std::fstream fs("d:/test.txt");
	std::stringstream ss;
	ss << "hello" << std::endl;
	std::copy(std::istream_iterator<char>(ss),
		std::istream_iterator<char>(),
		std::ostream_iterator<char>(fs));
	fs.close();
	return 0;
}

STDMETHODIMP MyObject::SomeMethod(...)
{
  CreateThread(NULL, 0, ThreadProc, this, 0, NULL);
  // Succeeds with S_OK
  FireEvent(L"Hello, world!");
  return S_OK;
}

DWORD WINAPI ThreadProc(LPVOID param)
{
  CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);
  MyObject* comObject = reinterpret_cast<MyObject*>(param);
  // Fails with 0x8000FFFF
  comObject->FireEvent(L"Hello, world!");
}

void MyObject::FireEvent(BSTR str)
{
  ...
  // Returns 0x8000FFFF if called from ThreadProc
  // Returns S_OK if called from SomeMethod
  pConnection->Invoke(dispid, IID_NULL, LOCALE_USER_DEFAULT, DISPATCH_METHOD, &params, NULL, NULL, NULL);
}