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Manual Pages  — INTRO


intro – introduction to system kernel interfaces



This section contains information about the interfaces and subroutines in the kernel.


Yes please.

We would like all code to be fully prototyped.

If your code compiles cleanly with cc -Wall we would feel happy about it. It is important to understand that this is not a question of just shutting up cc, it is a question about avoiding the things it complains about. To put it bluntly, do not hide the problem by casting and other obfuscating practices, solve the problem.


Believe it or not, there actually exists a guide for indentation and style. It is not generally applied though.

We would appreciate if people would pay attention to it, and at least not violate it blatantly.

We do not mind it too badly if you have your own style, but please make sure we can read it too.

Please take time to read style(9) for more information.


Some general rules exist:
  1. If a function is meant as a debugging aid in DDB, it should be enclosed in
    #ifdef DDB

    #endif /* DDB */

    And the name of the procedure should start with the prefix DDB_ to clearly identify the procedure as a debugger routine.


It is important to carefully consider the scope of symbols in the kernel. The default is to make everything static, unless some reason requires the opposite.

There are several reasons for this policy, the main one is that the kernel is one monolithic name-space, and pollution is not a good idea here either.

For device drivers and other modules that do not add new internal interfaces to the kernel, the entire source should be in one file if possible. That way all symbols can be made static.

If for some reason a module is split over multiple source files, then try to split the module along some major fault-line and consider using the number of global symbols as your guide. The fewer the better.




The intro section manual page appeared in FreeBSD 2.2 .

INTRO (9) December 13, 1995

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Please direct any comments about this manual page service to Ben Bullock. Privacy policy.

As soon as we started programming, we found to our surprise that it wasn't as easy to get programs right as we had thought. Debugging had to be discovered. I can remember the exact instant when I realized that a large part of my life from then on was going to be spent in finding mistakes in my own programs.
— Maurice Wilkes