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STYLE revision 1.4 
      1 $NetBSD: STYLE,v 1.4 1997/09/02 13:42:49 thorpej 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 option headers should be included first, and sorted, like:
     21 
     22 #include "opt_dec_3000_300.h"
     23 #include "opt_dec_3000_500.h"
     24 
     25 (2) All C sources should include <sys/cdefs.h> as the first header to
     26 be included after any option headers, with a line like:
     27 
     28 #include <sys/cdefs.h>			/* RCS ID & Copyright macro defns */
     29 
     30 (3) Nothing should include <sys/conf.h> directly.  Instead, <machine/conf.h>
     31 should be included.  It includes <sys/conf.h> and provides appropriate
     32 definitions for the machine-dependent devices and macros used by the Alpha
     33 port.
     34 
     35 
     36 RCS IDS
     37 
     38 (1) NetBSD RCS ID tags ($NetBSD: STYLE,v 1.4 1997/09/02 13:42:49 thorpej Exp $ tags) in C sources and headers should
     39 appear at the top of the file in a single-line comment of the form
     40 
     41 /*<space>$NetBSD: STYLE,v 1.4 1997/09/02 13:42:49 thorpej Exp $<space>*/
     42 
     43 which differs from the normal NetBSD style, in that it uses spaces
     44 rather than tabs to seperate the tag from the comment start and end
     45 delimiters.
     46 
     47 (2) All C and assembler sources should include an RCS ID tag which can
     48 be compiled into the binary, with a line like:
     49 
     50 __KERNEL_RCSID(0, "$NetBSD: STYLE,v 1.4 1997/09/02 13:42:49 thorpej Exp $");
     51 
     52 after the inclusion of cdefs.h.  Source files which include other source
     53 files should change the number '0' to a different number, so that it
     54 doesn't conflict with the RCS ID definitios in included sources.
     55 Generation of these RCS IDs is disabled if the kernel option
     56 NO_KERNEL_RCSIDS is defined.  (In some cases, picking the number to use
     57 may not be so straightforward, but the rule above usually works.)
     58 
     59 
     60 COMPILATION FLAGS
     61 
     62 By default, NetBSD/alpha kernel files are compiled with the following gcc
     63 warning flags:
     64 
     65 	-Werror
     66 	-Wall
     67 	-Wstrict-prototypes
     68 	-Wmissing-prototypes
     69 	-Wno-format
     70 
     71 NetBSD/alpha kernel code should compile cleanly with those flags.  At some
     72 point in the future (when the nonstandard extensions have been removed
     73 from the kernel printf() function), -Wformat will be re-enabled, so sources
     74 should be able to compile with it enabled as well.
     75 
     76 
     77 MACRO DEFINITIONS
     78 
     79 (1) Macros which use C blocks (i.e. are of the form "{ ... expressions
     80 ... }") should always be defined like:
     81 
     82 #define	MACRO(arg1, arg2, argN)					\
     83 do {								\
     84 	...							\
     85 	expressions						\
     86 	...							\
     87 } while (0)
     88 
     89 so that they behave like functions or macros which don't use blocks (e.g.
     90 for the purpose of "if (foo) MACRO(); else ...").
     91 
     92 
     93 BLOCKS AND EXPRESSIONS
     94 
     95 (1) Surround blocks with { and } more often than is absolutely necessary.
     96 For instance:
     97 
     98 	if (foo)
     99 		bar();
    100 
    101 is acceptable, but:
    102 
    103 	if (foo) {
    104 		bar();
    105 	}
    106 
    107 is preferred.  (In contrast, NetBSD KNF says that no braces are to be
    108 used for control statements with zero or one statements.)
    109 
    110 (2) Use extra parentheses when it makes expressions clearer.  For instance,
    111 
    112 	(foo == 10 && bar == 20)
    113 
    114 is acceptable, but:
    115 
    116 	((foo == 10) && (bar == 20))
    117 
    118 is preferred.  (In contrast, NetBSD KNF says to avoid using parentheses
    119 except where necessary unless the expression is very confusing without
    120 them.)
    121