如何发现DLL是否在Windows服务的上下文中运行？

Question

I am writing a DLL which may run in the context of a service and may be loaded into a standard win32 process. How can I detect whether it is running in the context of a service or in the context of a standard win32 process ?

Answer 1

According to Session 0 Isolation , introduced in Vista, Windows Services run in session 0. To determine if the process is executing in session 0 you could use ProcessIdToSessionId function:

DWORD session_id;
if (ProcessIdToSessionId(GetCurrentProcessId(), &session_id))
{
    std::cout << "session_id=" << session_id << "\n";
}
else
{
    std::cout << "Failed : " << GetLastError() << "\n";
}

In relation to your comment regarding GUI, to quote directly from the linked document:

Because Session 0 is no longer a user session, services that are running in Session 0 do not have access to the video driver. This means that any attempt that a service makes to render graphics fails.