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STYLE revision 1.2 
      1 $NetBSD: STYLE,v 1.2 1997/04/08 00:18:25 cgd Exp $
      2 
      3 Style guide for NetBSD/alpha kernel files.
      4 
      5 This file is meant to supplement the NetBSD KNF style guide (which covers
      6 most of the rest of the system, and can be found in /usr/share/misc/style).
      7 
      8 
      9 SECTIONS
     10 
     11 	* INCLUDE FILES
     12 	* RCS IDS
     13 	* COMPILATION FLAGS
     14 	* MACRO DEFINITIONS
     15 	* BLOCKS AND EXPRESSIONS
     16 
     17 
     18 INCLUDE FILES
     19 
     20 (1) All C and assembly sources (which are not included by other C or
     21 assembly sources) sources should include <machine/options.h> as the
     22 first header to be included, with a line like:
     23 
     24 #include <machine/options.h>		/* Pull in config options headers */
     25 
     26 (2) All C sources should include <sys/cdefs.h> (after <machine/options.h>,
     27 when it is included, otherwise as the first header to be included), with
     28 a line like:
     29 
     30 #include <sys/cdefs.h>			/* RCS ID & Copyright macro defns */
     31 
     32 (3) Nothing should include <sys/conf.h> directly.  Instead, <machine/conf.h>
     33 should be included.  It includes <sys/conf.h> and provides appropriate
     34 definitions for the machine-dependent devices and macros used by the Alpha
     35 port.
     36 
     37 
     38 RCS IDS
     39 
     40 (1) NetBSD RCS ID tags ($NetBSD: STYLE,v 1.2 1997/04/08 00:18:25 cgd Exp $ tags) in C sources and headers should
     41 appear at the top of the file in a single-line comment of the form
     42 
     43 /*<space>$NetBSD: STYLE,v 1.2 1997/04/08 00:18:25 cgd Exp $<space>*/
     44 
     45 which differs from the normal NetBSD style, in that it uses spaces
     46 rather than tabs to seperate the tag from the comment start and end
     47 delimiters.
     48 
     49 (2) All C and assembler sources should include an RCS ID tag which can
     50 be compiled into the binary, with a line like:
     51 
     52 __KERNEL_RCSID(0, "$NetBSD: STYLE,v 1.2 1997/04/08 00:18:25 cgd Exp $");
     53 
     54 after the inclusion of cdefs.h.  Source files which include other source
     55 files should change the number '0' to a different number, so that it
     56 doesn't conflict with the RCS ID definitios in included sources.
     57 Generation of these RCS IDs is disabled if the kernel option
     58 NO_KERNEL_RCSIDS is defined.  (In some cases, picking the number to use
     59 may not be so straightforward, but the rule above usually works.)
     60 
     61 
     62 COMPILATION FLAGS
     63 
     64 By default, NetBSD/alpha kernel files are compiled with the following gcc
     65 warning flags:
     66 
     67 	-Werror
     68 	-Wall
     69 	-Wstrict-prototypes
     70 	-Wmissing-prototypes
     71 	-Wno-format
     72 
     73 NetBSD/alpha kernel code should compile cleanly with those flags.  At some
     74 point in the future (when the nonstandard extensions have been removed
     75 from the kernel printf() function), -Wformat will be re-enabled, so sources
     76 should be able to compile with it enabled as well.
     77 
     78 
     79 MACRO DEFINITIONS
     80 
     81 (1) Macros which use C blocks (i.e. are of the form "{ ... expressions
     82 ... }") should always be defined like:
     83 
     84 #define	MACRO(arg1, arg2, argN)					\
     85 do {								\
     86 	...							\
     87 	expressions						\
     88 	...							\
     89 } while (0)
     90 
     91 so that they behave like functions or macros which don't use blocks (e.g.
     92 for the purpose of "if (foo) MACRO(); else ...").
     93 
     94 
     95 BLOCKS AND EXPRESSIONS
     96 
     97 (1) Surround blocks with { and } more often than is absolutely necessary.
     98 For instance:
     99 
    100 	if (foo)
    101 		bar();
    102 
    103 is acceptable, but:
    104 
    105 	if (foo) {
    106 		bar();
    107 	}
    108 
    109 is preferred.  (In contrast, NetBSD KNF says that no braces are to be
    110 used for control statements with zero or one statements.)
    111 
    112 (2) Use extra parentheses when it makes expressions clearer.  For instance,
    113 
    114 	(foo == 10 && bar == 20)
    115 
    116 is acceptable, but:
    117 
    118 	((foo == 10) && (bar == 20))
    119 
    120 is preferred.  (In contrast, NetBSD KNF says to avoid using parentheses
    121 except where necessary unless the expression is very confusing without
    122 them.)
    123