Kernel Programming Style
As described in “Keep Out”, programming in the kernel is fraught with hazards that can cause instability, crashes, or security holes. In addition to these issues, programming in the kernel has the potential for compatibility problems. If you program only to the interfaces discussed in this document or other Apple documents, you will avoid the majority of these.
However, even limiting yourself to documented interfaces does not protect you from a handful of pitfalls. The biggest potential problem that you face is namespace collision, which occurs when your function, variable, or class name is the same as someone else’s. Since this makes one kernel extension or the other fail to load correctly (in a non-deterministic fashion), Apple has established function naming conventions for C and C++ code within the kernel. These are described in “Standard C Naming Conventions” and “C++ Naming Conventions”, respectively.
In addition to compatibility problems, kernel extensions that misbehave can also dramatically decrease the system’s overall performance or cause crashes. Some of these issues are described in “Performance and Stability Tips”. For more thorough coverage of performance and stability, you should also read the chapters “Security Considerations” and “Performance Considerations”.
