Style notes added to HACKING

Russ Allbery rra at
Sun Mar 10 06:26:27 UTC 2002

Don't know when people will get this; ISC mail seems to be temporarily

I've added the following notes to the style section of HACKING:

   *  Write in regular ANSI C whenever possible.  Use the normal ANSI and
      POSIX constructs and use autoconf or portability wrappers to fix
      things up beforehand so that the code itself can read like regular
      ANSI or POSIX code.  Code should be written so that it works as
      expected on a modern platform and is fixed up with portability tricks
      for older platforms, not the other way around.  You may assume an
      ANSI C compiler.

      Try to use const wherever appropriate.  Don't use register; modern
      compilers will do as good of a job as you will in choosing what to
      put into a register.  Don't bother with restrict (at least yet).

   *  Avoid #ifdef and friends whenever possible.  Particularly avoid using
      them in the middle of code blocks.  Try to hide all portability
      preprocessor magic in header files or in portability code in lib. 
      When something just has to be done two completely different ways
      depending on the platform or compile options or the like, try to
      abstract that functionality out into a generic function and provide
      two separate implementations using #ifdef; then the main code can
      just call that function.

      If you do have to use preprocessor defines, note that if you always
      define them to either 0 or 1 (never use #define without a second
      argument), you can use the preprocessor define in a regular if
      statement rather than using #if or #ifdef.  Make use of this instead
      of #ifdef when possible, since that way the compiler will still
      syntax-check the other branch for you and it makes it far easier to
      convert the code to use a run-time check if necessary. 
      (Unfortunately, this trick can't be used if one branch may call
      functions unavailable on a particular platform.)

Russ Allbery (rra at             <>

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