Chapter 14: Debugging Windows Services and DLLs That Load into Services

Overview

Next to device drivers, the hardest code to debug involves Microsoft Windows services and DLLs that load into services. You might think that because services are really just user-mode processes without a user interface, debugging them would be as easy as debugging a console application. Unfortunately, the story isn't that simple. In fact, so many issues come into play with Windows services and with DLLs that load into services, especially issues related to Windows security, that you might find yourself wanting to pull out your hair in frustration trying to work with them. In the early days of Microsoft Windows NT, very few developers wrote services or even knew what they were. However, in today's world of COM+, Microsoft Internet Information Services (IIS), Microsoft Exchange Server extensions, and Windows Clustering, many developers must start dealing with services—and debugging them.

In this chapter, I'll provide an overview of the basic characteristics of services. To understand how to debug services and DLLs that load into services, such as ISAPI filters and extensions, you need to know how services operate. I'll then explain issues directly related to debugging services. As I walk you through the different stages of debugging a service, I'll point out issues that apply to specific Microsoft service technologies.