Question

Let’s say I have the following code:

typedef std::function<void ()> func_type;

void some_func()
{
  // Irrelevant stuff here. Might take some time...
}

DWORD WINAPI thread_proc(LPVOID lpParameter)
{
  func_type& func = *static_cast<func_type*>(lpParameter);

  func();

  return 0;
}

int main()
{
  HANDLE handle;

  {
    std::function<void ()> my_func(some_func);

    handle = ::CreateThread(NULL, 0, &thread_proc, &my_func, 0, NULL);

    // Here we consider my_func won't be destroyed before its operator() is called in the other thread.
    // I know nothing guarantees that, but let's just say it does for this sample.
  }

  ::WaitForSingleObject(handle, INFINITE);

  return EXIT_SUCCESS;
}

My current implementation seems to work, but this doesn’t prove that I’m not facing undefined behavior.

Here my_func might be destroyed before the call to its operator() returns. But since I’m not refering to my_func anywhere in some_func(), is it really a problem ?

Note: I cannot use std::thread or boost::thread unfortunately. I wish I could.

Answer 1

If it gets destroyed before func() happens, then you’re calling a member function on an invalid object. You need to make a copy that will live at least until func() call.